When a P9 sPAPR VM boots, the CAS negotiation process determines which
interrupt mode to use (XICS legacy or XIVE native) and invokes a
machine reset to activate the chosen mode.

To be able to switch from one interrupt mode to another, we introduce
the capability to release a KVM device without destroying the VM. The
KVM device interface is extended with a new 'release' method which is
called when the file descriptor of the device is closed.

Once 'release' is called, the 'destroy' method will not be called
anymore as the device is removed from the device list of the VM.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Full support for the XIVE native exploitation mode is now available,
advertise the capability KVM_CAP_PPC_IRQ_XIVE for guests running on
PowerNV KVM Hypervisors only. Support for nested guests (pseries KVM
Hypervisor) is not yet available. XIVE should also have been activated
which is default setting on POWER9 systems running a recent Linux
kernel.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The KVM XICS-over-XIVE device and the proposed KVM XIVE native device
implement an IRQ space for the guest using the generic IPI interrupts
of the XIVE IC controller. These interrupts are allocated at the OPAL
level and "mapped" into the guest IRQ number space in the range 0-0x1FFF.
Interrupt management is performed in the XIVE way: using loads and
stores on the addresses of the XIVE IPI interrupt ESB pages.

Both KVM devices share the same internal structure caching information
on the interrupts, among which the xive_irq_data struct containing the
addresses of the IPI ESB pages and an extra one in case of pass-through.
The later contains the addresses of the ESB pages of the underlying HW
controller interrupts, PHB4 in all cases for now.

A guest, when running in the XICS legacy interrupt mode, lets the KVM
XICS-over-XIVE device "handle" interrupt management, that is to
perform the loads and stores on the addresses of the ESB pages of the
guest interrupts. However, when running in XIVE native exploitation
mode, the KVM XIVE native device exposes the interrupt ESB pages to
the guest and lets the guest perform directly the loads and stores.

The VMA exposing the ESB pages make use of a custom VM fault handler
which role is to populate the VMA with appropriate pages. When a fault
occurs, the guest IRQ number is deduced from the offset, and the ESB
pages of associated XIVE IPI interrupt are inserted in the VMA (using
the internal structure caching information on the interrupts).

Supporting device passthrough in the guest running in XIVE native
exploitation mode adds some extra refinements because the ESB pages
of a different HW controller (PHB4) need to be exposed to the guest
along with the initial IPI ESB pages of the XIVE IC controller. But
the overall mechanic is the same.

When the device HW irqs are mapped into or unmapped from the guest
IRQ number space, the passthru_irq helpers, kvmppc_xive_set_mapped()
and kvmppc_xive_clr_mapped(), are called to record or clear the
passthrough interrupt information and to perform the switch.

The approach taken by this patch is to clear the ESB pages of the
guest IRQ number being mapped and let the VM fault handler repopulate.
The handler will insert the ESB page corresponding to the HW interrupt
of the device being passed-through or the initial IPI ESB page if the
device is being removed.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Each source is associated with an Event State Buffer (ESB) with a
even/odd pair of pages which provides commands to manage the source:
to trigger, to EOI, to turn off the source for instance.

The custom VM fault handler will deduce the guest IRQ number from the
offset of the fault, and the ESB page of the associated XIVE interrupt
will be inserted into the VMA using the internal structure caching
information on the interrupts.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Each thread has an associated Thread Interrupt Management context
composed of a set of registers. These registers let the thread handle
priority management and interrupt acknowledgment. The most important
are :

    - Interrupt Pending Buffer     (IPB)
    - Current Processor Priority   (CPPR)
    - Notification Source Register (NSR)

They are exposed to software in four different pages each proposing a
view with a different privilege. The first page is for the physical
thread context and the second for the hypervisor. Only the third
(operating system) and the fourth (user level) are exposed the guest.

A custom VM fault handler will populate the VMA with the appropriate
pages, which should only be the OS page for now.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Some KVM devices will want to handle special mappings related to the
underlying HW. For instance, the XIVE interrupt controller of the
POWER9 processor has MMIO pages for thread interrupt management and
for interrupt source control that need to be exposed to the guest when
the OS has the required support.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The state of the thread interrupt management registers needs to be
collected for migration. These registers are cached under the
'xive_saved_state.w01' field of the VCPU when the VPCU context is
pulled from the HW thread. An OPAL call retrieves the backup of the
IPB register in the underlying XIVE NVT structure and merges it in the
KVM state.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

When migration of a VM is initiated, a first copy of the RAM is
transferred to the destination before the VM is stopped, but there is
no guarantee that the EQ pages in which the event notifications are
queued have not been modified.

To make sure migration will capture a consistent memory state, the
XIVE device should perform a XIVE quiesce sequence to stop the flow of
event notifications and stabilize the EQs. This is the purpose of the
KVM_DEV_XIVE_EQ_SYNC control which will also marks the EQ pages dirty
to force their transfer.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This control will be used by the H_INT_SYNC hcall from QEMU to flush
event notifications on the XIVE IC owning the source.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This control is to be used by the H_INT_RESET hcall from QEMU. Its
purpose is to clear all configuration of the sources and EQs. This is
necessary in case of a kexec (for a kdump kernel for instance) to make
sure that no remaining configuration is left from the previous boot
setup so that the new kernel can start safely from a clean state.

The queue 7 is ignored when the XIVE device is configured to run in
single escalation mode. Prio 7 is used by escalations.

The XIVE VP is kept enabled as the vCPU is still active and connected
to the XIVE device.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

These controls will be used by the H_INT_SET_QUEUE_CONFIG and
H_INT_GET_QUEUE_CONFIG hcalls from QEMU to configure the underlying
Event Queue in the XIVE IC. They will also be used to restore the
configuration of the XIVE EQs and to capture the internal run-time
state of the EQs. Both 'get' and 'set' rely on an OPAL call to access
the EQ toggle bit and EQ index which are updated by the XIVE IC when
event notifications are enqueued in the EQ.

The value of the guest physical address of the event queue is saved in
the XIVE internal xive_q structure for later use. That is when
migration needs to mark the EQ pages dirty to capture a consistent
memory state of the VM.

To be noted that H_INT_SET_QUEUE_CONFIG does not require the extra
OPAL call setting the EQ toggle bit and EQ index to configure the EQ,
but restoring the EQ state will.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This control will be used by the H_INT_SET_SOURCE_CONFIG hcall from
QEMU to configure the target of a source and also to restore the
configuration of a source when migrating the VM.

The XIVE source interrupt structure is extended with the value of the
Effective Interrupt Source Number. The EISN is the interrupt number
pushed in the event queue that the guest OS will use to dispatch
events internally. Caching the EISN value in KVM eases the test when
checking if a reconfiguration is indeed needed.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The XIVE KVM device maintains a list of interrupt sources for the VM
which are allocated in the pool of generic interrupts (IPIs) of the
main XIVE IC controller. These are used for the CPU IPIs as well as
for virtual device interrupts. The IRQ number space is defined by
QEMU.

The XIVE device reuses the source structures of the XICS-on-XIVE
device for the source blocks (2-level tree) and for the source
interrupts. Under XIVE native, the source interrupt caches mostly
configuration information and is less used than under the XICS-on-XIVE
device in which hcalls are still necessary at run-time.

When a source is initialized in KVM, an IPI interrupt source is simply
allocated at the OPAL level and then MASKED. KVM only needs to know
about its type: LSI or MSI.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The user interface exposes a new capability KVM_CAP_PPC_IRQ_XIVE to
let QEMU connect the vCPU presenters to the XIVE KVM device if
required. The capability is not advertised for now as the full support
for the XIVE native exploitation mode is not yet available. When this
is case, the capability will be advertised on PowerNV Hypervisors
only. Nested guests (pseries KVM Hypervisor) are not supported.

Internally, the interface to the new KVM device is protected with a
new interrupt mode: KVMPPC_IRQ_XIVE.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This is the basic framework for the new KVM device supporting the XIVE
native exploitation mode. The user interface exposes a new KVM device
to be created by QEMU, only available when running on a L0 hypervisor.
Support for nested guests is not available yet.

The XIVE device reuses the device structure of the XICS-on-XIVE device
as they have a lot in common. That could possibly change in the future
if the need arise.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This merges in the ppc-kvm topic branch from the powerpc tree to get
patches which touch both general powerpc code and KVM code, one of
which is a prerequisite for following patches.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

On POWER9 and later processors where the host can schedule vcpus on a
per thread basis, there is a streamlined entry path used when the guest
is radix. This entry path saves/restores the fp and vr state in
kvmhv_p9_guest_entry() by calling store_[fp/vr]_state() and
load_[fp/vr]_state(). This is the same as the old entry path however the
old entry path also saved/restored the VRSAVE register, which isn't done
in the new entry path.

This means that the vrsave register is now volatile across guest exit,
which is an incorrect change in behaviour.

Fix this by saving/restoring the vrsave register in kvmhv_p9_guest_entry().
This restores the old, correct, behaviour.

Fixes: 95a6432c ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

When running on POWER9 with kvm_hv.indep_threads_mode = N and the host
in SMT1 mode, KVM will run guest VCPUs on offline secondary threads.
If those guests are in radix mode, we fail to load the LPID and flush
the TLB if necessary, leading to the guest crashing with an
unsupported MMU fault.  This arises from commit 9a4506e1 ("KVM:
PPC: Book3S HV: Make radix handle process scoped LPID flush in C,
with relocation on", 2018-05-17), which didn't consider the case
where indep_threads_mode = N.

For simplicity, this makes the real-mode guest entry path flush the
TLB in the same place for both radix and hash guests, as we did before
9a4506e1, though the code is now C code rather than assembly code.
We also have the radix TLB flush open-coded rather than calling
radix__local_flush_tlb_lpid_guest(), because the TLB flush can be
called in real mode, and in real mode we don't want to invoke the
tracepoint code.

Fixes: 9a4506e1 ("KVM: PPC: Book3S HV: Make radix handle process scoped LPID flush in C, with relocation on")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This replaces assembler code in book3s_hv_rmhandlers.S that checks
the kvm->arch.need_tlb_flush cpumask and optionally does a TLB flush
with C code in book3s_hv_builtin.c.  Note that unlike the radix
version, the hash version doesn't do an explicit ERAT invalidation
because we will invalidate and load up the SLB before entering the
guest, and that will invalidate the ERAT.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The code in book3s_hv_rmhandlers.S that pushes the XIVE virtual CPU
context to the hardware currently assumes it is being called in real
mode, which is usually true.  There is however a path by which it can
be executed in virtual mode, in the case where indep_threads_mode = N.
A virtual CPU executing on an offline secondary thread can take a
hypervisor interrupt in virtual mode and return from the
kvmppc_hv_entry() call after the kvm_secondary_got_guest label.
It is possible for it to be given another vcpu to execute before it
gets to execute the stop instruction.  In that case it will call
kvmppc_hv_entry() for the second VCPU in virtual mode, and the XIVE
vCPU push code will be executed in virtual mode.  The result in that
case will be a host crash due to an unexpected data storage interrupt
caused by executing the stdcix instruction in virtual mode.

This fixes it by adding a code path for virtual mode, which uses the
virtual TIMA pointer and normal load/store instructions.

[paulus@ozlabs.org - wrote patch description]
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This fixes a bug in the XICS emulation on POWER9 machines which is
triggered by the guest doing a H_IPI with priority = 0 (the highest
priority).  What happens is that the notification interrupt arrives
at the destination at priority zero.  The loop in scan_interrupts()
sees that a priority 0 interrupt is pending, but because xc->mfrr is
zero, we break out of the loop before taking the notification
interrupt out of the queue and EOI-ing it.  (This doesn't happen
when xc->mfrr != 0; in that case we process the priority-0 notification
interrupt on the first iteration of the loop, and then break out of
a subsequent iteration of the loop with hirq == XICS_IPI.)

To fix this, we move the prio >= xc->mfrr check down to near the end
of the loop.  However, there are then some other things that need to
be adjusted.  Since we are potentially handling the notification
interrupt and also delivering an IPI to the guest in the same loop
iteration, we need to update pending and handle any q->pending_count
value before the xc->mfrr check, rather than at the end of the loop.
Also, we need to update the queue pointers when we have processed and
EOI-ed the notification interrupt, since we may not do it later.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

I made the same typo when trying to grep for uses of smp_wmb and figured
I might as well fix it.
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

We already allocate hardware TCE tables in multiple levels and skip
intermediate levels when we can, now it is a turn of the KVM TCE tables.
Thankfully these are allocated already in 2 levels.

This moves the table's last level allocation from the creating helper to
kvmppc_tce_put() and kvm_spapr_tce_fault(). Since such allocation cannot
be done in real mode, this creates a virtual mode version of
kvmppc_tce_put() which handles allocations.

This adds kvmppc_rm_ioba_validate() to do an additional test if
the consequent kvmppc_tce_put() needs a page which has not been allocated;
if this is the case, we bail out to virtual mode handlers.

The allocations are protected by a new mutex as kvm->lock is not suitable
for the task because the fault handler is called with the mmap_sem held
but kvmhv_setup_mmu() locks kvm->lock and mmap_sem in the reverse order.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The kvmppc_tce_to_ua() helper is called from real and virtual modes
and it works fine as long as CONFIG_DEBUG_LOCKDEP is not enabled.
However if the lockdep debugging is on, the lockdep will most likely break
in kvm_memslots() because of srcu_dereference_check() so we need to use
PPC-own kvm_memslots_raw() which uses realmode safe
rcu_dereference_raw_notrace().

This creates a realmode copy of kvmppc_tce_to_ua() which replaces
kvm_memslots() with kvm_memslots_raw().

Since kvmppc_rm_tce_to_ua() becomes static and can only be used inside
HV KVM, this moves it earlier under CONFIG_KVM_BOOK3S_HV_POSSIBLE.

This moves truly virtual-mode kvmppc_tce_to_ua() to where it belongs and
drops the prmap parameter which was never used in the virtual mode.

Fixes: d3695aa4 ("KVM: PPC: Add support for multiple-TCE hcalls", 2016-02-15)
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

The trace_hardirqs_on() sets current->hardirqs_enabled and from here
the lockdep assumes interrupts are enabled although they are remain
disabled until the context switches to the guest. Consequent
srcu_read_lock() checks the flags in rcu_lock_acquire(), observes
disabled interrupts and prints a warning (see below).

This moves trace_hardirqs_on/off closer to __kvmppc_vcore_entry to
prevent lockdep from being confused.

DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
WARNING: CPU: 16 PID: 8038 at kernel/locking/lockdep.c:4128 check_flags.part.25+0x224/0x280
[...]
NIP [c000000000185b84] check_flags.part.25+0x224/0x280
LR [c000000000185b80] check_flags.part.25+0x220/0x280
Call Trace:
[c000003fec253710] [c000000000185b80] check_flags.part.25+0x220/0x280 (unreliable)
[c000003fec253780] [c000000000187ea4] lock_acquire+0x94/0x260
[c000003fec253840] [c00800001a1e9768] kvmppc_run_core+0xa60/0x1ab0 [kvm_hv]
[c000003fec253a10] [c00800001a1ed944] kvmppc_vcpu_run_hv+0x73c/0xec0 [kvm_hv]
[c000003fec253ae0] [c00800001a1095dc] kvmppc_vcpu_run+0x34/0x48 [kvm]
[c000003fec253b00] [c00800001a1056bc] kvm_arch_vcpu_ioctl_run+0x2f4/0x400 [kvm]
[c000003fec253b90] [c00800001a0f3618] kvm_vcpu_ioctl+0x460/0x850 [kvm]
[c000003fec253d00] [c00000000041c4f4] do_vfs_ioctl+0xe4/0x930
[c000003fec253db0] [c00000000041ce04] ksys_ioctl+0xc4/0x110
[c000003fec253e00] [c00000000041ce78] sys_ioctl+0x28/0x80
[c000003fec253e20] [c00000000000b5a4] system_call+0x5c/0x70
Instruction dump:
419e0034 3d220004 39291730 81290000 2f890000 409e0020 3c82ffc6 3c62ffc5
3884be70 386329c0 4bf6ea71 60000000 <0fe00000> 3c62ffc6 3863be90 4801273d
irq event stamp: 1025
hardirqs last  enabled at (1025): [<c00800001a1e9728>] kvmppc_run_core+0xa20/0x1ab0 [kvm_hv]
hardirqs last disabled at (1024): [<c00800001a1e9358>] kvmppc_run_core+0x650/0x1ab0 [kvm_hv]
softirqs last  enabled at (0): [<c0000000000f1210>] copy_process.isra.4.part.5+0x5f0/0x1d00
softirqs last disabled at (0): [<0000000000000000>]           (null)
---[ end trace 31180adcc848993e ]---
possible reason: unannotated irqs-off.
irq event stamp: 1025
hardirqs last  enabled at (1025): [<c00800001a1e9728>] kvmppc_run_core+0xa20/0x1ab0 [kvm_hv]
hardirqs last disabled at (1024): [<c00800001a1e9358>] kvmppc_run_core+0x650/0x1ab0 [kvm_hv]
softirqs last  enabled at (0): [<c0000000000f1210>] copy_process.isra.4.part.5+0x5f0/0x1d00
softirqs last disabled at (0): [<0000000000000000>]           (null)

Fixes: 8b24e69f ("KVM: PPC: Book3S HV: Close race with testing for signals on guest entry", 2017-06-26)
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Implement a real mode handler for the H_CALL H_PAGE_INIT which can be
used to zero or copy a guest page. The page is defined to be 4k and must
be 4k aligned.

The in-kernel real mode handler halves the time to handle this H_CALL
compared to handling it in userspace for a hash guest.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Implement a virtual mode handler for the H_CALL H_PAGE_INIT which can be
used to zero or copy a guest page. The page is defined to be 4k and must
be 4k aligned.

The in-kernel handler halves the time to handle this H_CALL compared to
handling it in userspace for a radix guest.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

This adds a flag so that the DAWR can be enabled on P9 via:
  echo Y > /sys/kernel/debug/powerpc/dawr_enable_dangerous

The DAWR was previously force disabled on POWER9 in:
  96541531 powerpc: Disable DAWR in the base POWER9 CPU features
Also see Documentation/powerpc/DAWR-POWER9.txt

This is a dangerous setting, USE AT YOUR OWN RISK.

Some users may not care about a bad user crashing their box
(ie. single user/desktop systems) and really want the DAWR.  This
allows them to force enable DAWR.

This flag can also be used to disable DAWR access. Once this is
cleared, all DAWR access should be cleared immediately and your
machine once again safe from crashing.

Userspace may get confused by toggling this. If DAWR is force
enabled/disabled between getting the number of breakpoints (via
PTRACE_GETHWDBGINFO) and setting the breakpoint, userspace will get an
inconsistent view of what's available. Similarly for guests.

For the DAWR to be enabled in a KVM guest, the DAWR needs to be force
enabled in the host AND the guest. For this reason, this won't work on
POWERVM as it doesn't allow the HCALL to work. Writes of 'Y' to the
dawr_enable_dangerous file will fail if the hypervisor doesn't support
writing the DAWR.

To double check the DAWR is working, run this kernel selftest:
  tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
Any errors/failures/skips mean something is wrong.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The support for XIVE native exploitation mode in Linux/KVM needs a
couple more OPAL calls to get and set the state of the XIVE internal
structures being used by a sPAPR guest.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Guest physical to user address translation uses KVM memslots and reading
these requires holding the kvm->srcu lock. However recently introduced
kvmppc_tce_validate() broke the rule (see the lockdep warning below).

This moves srcu_read_lock(&vcpu->kvm->srcu) earlier to protect
kvmppc_tce_validate() as well.

=============================
WARNING: suspicious RCU usage
5.1.0-rc2-le_nv2_aikATfstn1-p1 #380 Not tainted
-----------------------------
include/linux/kvm_host.h:605 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by qemu-system-ppc/8020:
 #0: 0000000094972fe9 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0xdc/0x850 [kvm]

stack backtrace:
CPU: 44 PID: 8020 Comm: qemu-system-ppc Not tainted 5.1.0-rc2-le_nv2_aikATfstn1-p1 #380
Call Trace:
[c000003fece8f740] [c000000000bcc134] dump_stack+0xe8/0x164 (unreliable)
[c000003fece8f790] [c000000000181be0] lockdep_rcu_suspicious+0x130/0x170
[c000003fece8f810] [c0000000000d5f50] kvmppc_tce_to_ua+0x280/0x290
[c000003fece8f870] [c00800001a7e2c78] kvmppc_tce_validate+0x80/0x1b0 [kvm]
[c000003fece8f8e0] [c00800001a7e3fac] kvmppc_h_put_tce+0x94/0x3e4 [kvm]
[c000003fece8f9a0] [c00800001a8baac4] kvmppc_pseries_do_hcall+0x30c/0xce0 [kvm_hv]
[c000003fece8fa10] [c00800001a8bd89c] kvmppc_vcpu_run_hv+0x694/0xec0 [kvm_hv]
[c000003fece8fae0] [c00800001a7d95dc] kvmppc_vcpu_run+0x34/0x48 [kvm]
[c000003fece8fb00] [c00800001a7d56bc] kvm_arch_vcpu_ioctl_run+0x2f4/0x400 [kvm]
[c000003fece8fb90] [c00800001a7c3618] kvm_vcpu_ioctl+0x460/0x850 [kvm]
[c000003fece8fd00] [c00000000041c4f4] do_vfs_ioctl+0xe4/0x930
[c000003fece8fdb0] [c00000000041ce04] ksys_ioctl+0xc4/0x110
[c000003fece8fe00] [c00000000041ce78] sys_ioctl+0x28/0x80
[c000003fece8fe20] [c00000000000b5a4] system_call+0x5c/0x70

Fixes: 42de7b9e ("KVM: PPC: Validate TCEs against preregistered memory page sizes", 2018-09-10)
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

There is a hardware bug in some POWER9 processors where a treclaim in
fake suspend mode can cause an inconsistency in the XER[SO] bit across
the threads of a core, the workaround being to force the core into SMT4
when doing the treclaim.

The FAKE_SUSPEND bit (bit 10) in the PSSCR is used to control whether a
thread is in fake suspend or real suspend. The important difference here
being that thread reconfiguration is blocked in real suspend but not
fake suspend mode.

When we exit a guest which was in fake suspend mode, we force the core
into SMT4 while we do the treclaim in kvmppc_save_tm_hv().
However on the new exit path introduced with the function
kvmhv_run_single_vcpu() we restore the host PSSCR before calling
kvmppc_save_tm_hv() which means that if we were in fake suspend mode we
put the thread into real suspend mode when we clear the
PSSCR[FAKE_SUSPEND] bit. This means that we block thread reconfiguration
and the thread which is trying to get the core into SMT4 before it can
do the treclaim spins forever since it itself is blocking thread
reconfiguration. The result is that that core is essentially lost.

This results in a trace such as:
[   93.512904] CPU: 7 PID: 13352 Comm: qemu-system-ppc Not tainted 5.0.0 #4
[   93.512905] NIP:  c000000000098a04 LR: c0000000000cc59c CTR: 0000000000000000
[   93.512908] REGS: c000003fffd2bd70 TRAP: 0100   Not tainted  (5.0.0)
[   93.512908] MSR:  9000000302883033 <SF,HV,VEC,VSX,FP,ME,IR,DR,RI,LE,TM[SE]>  CR: 22222444  XER: 00000000
[   93.512914] CFAR: c000000000098a5c IRQMASK: 3
[   93.512915] PACATMSCRATCH: 0000000000000001
[   93.512916] GPR00: 0000000000000001 c000003f6cc1b830 c000000001033100 0000000000000004
[   93.512928] GPR04: 0000000000000004 0000000000000002 0000000000000004 0000000000000007
[   93.512930] GPR08: 0000000000000000 0000000000000004 0000000000000000 0000000000000004
[   93.512932] GPR12: c000203fff7fc000 c000003fffff9500 0000000000000000 0000000000000000
[   93.512935] GPR16: 2000000000300375 000000000000059f 0000000000000000 0000000000000000
[   93.512951] GPR20: 0000000000000000 0000000000080053 004000000256f41f c000003f6aa88ef0
[   93.512953] GPR24: c000003f6aa89100 0000000000000010 0000000000000000 0000000000000000
[   93.512956] GPR28: c000003f9e9a0800 0000000000000000 0000000000000001 c000203fff7fc000
[   93.512959] NIP [c000000000098a04] pnv_power9_force_smt4_catch+0x1b4/0x2c0
[   93.512960] LR [c0000000000cc59c] kvmppc_save_tm_hv+0x40/0x88
[   93.512960] Call Trace:
[   93.512961] [c000003f6cc1b830] [0000000000080053] 0x80053 (unreliable)
[   93.512965] [c000003f6cc1b8a0] [c00800001e9cb030] kvmhv_p9_guest_entry+0x508/0x6b0 [kvm_hv]
[   93.512967] [c000003f6cc1b940] [c00800001e9cba44] kvmhv_run_single_vcpu+0x2dc/0xb90 [kvm_hv]
[   93.512968] [c000003f6cc1ba10] [c00800001e9cc948] kvmppc_vcpu_run_hv+0x650/0xb90 [kvm_hv]
[   93.512969] [c000003f6cc1bae0] [c00800001e8f620c] kvmppc_vcpu_run+0x34/0x48 [kvm]
[   93.512971] [c000003f6cc1bb00] [c00800001e8f2d4c] kvm_arch_vcpu_ioctl_run+0x2f4/0x400 [kvm]
[   93.512972] [c000003f6cc1bb90] [c00800001e8e3918] kvm_vcpu_ioctl+0x460/0x7d0 [kvm]
[   93.512974] [c000003f6cc1bd00] [c0000000003ae2c0] do_vfs_ioctl+0xe0/0x8e0
[   93.512975] [c000003f6cc1bdb0] [c0000000003aeb24] ksys_ioctl+0x64/0xe0
[   93.512978] [c000003f6cc1be00] [c0000000003aebc8] sys_ioctl+0x28/0x80
[   93.512981] [c000003f6cc1be20] [c00000000000b3a4] system_call+0x5c/0x70
[   93.512983] Instruction dump:
[   93.512986] 419dffbc e98c0000 2e8b0000 38000001 60000000 60000000 60000000 40950068
[   93.512993] 392bffff 39400000 79290020 39290001 <7d2903a6> 60000000 60000000 7d235214

To fix this we preserve the PSSCR[FAKE_SUSPEND] bit until we call
kvmppc_save_tm_hv() which will mean the core can get into SMT4 and
perform the treclaim. Note kvmppc_save_tm_hv() clears the
PSSCR[FAKE_SUSPEND] bit again so there is no need to explicitly do that.

Fixes: 95a6432c ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Merge tag 'kvmarm-fixes-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-master

KVM/ARM fixes for 5.1

- Fix THP handling in the presence of pre-existing PTEs
- Honor request for PTE mappings even when THPs are available
- GICv4 performance improvement
- Take the srcu lock when writing to guest-controlled ITS data structures
- Reset the virtual PMU in preemptible context
- Various cleanups

The documentation does not mention how to delete a slot, add the
information.
Reported-by: Nathaniel McCallum <npmccallum@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

The series to add memcg accounting to KVM allocations[1] states:

  There are many KVM kernel memory allocations which are tied to the
  life of the VM process and should be charged to the VM process's
  cgroup.

While it is correct to account KVM kernel allocations to the cgroup of
the process that created the VM, it's technically incorrect to state
that the KVM kernel memory allocations are tied to the life of the VM
process.  This is because the VM itself, i.e. struct kvm, is not tied to
the life of the process which created it, rather it is tied to the life
of its associated file descriptor.  In other words, kvm_destroy_vm() is
not invoked until fput() decrements its associated file's refcount to
zero.  A simple example is to fork() in Qemu and have the child sleep
indefinitely; kvm_destroy_vm() isn't called until Qemu closes its file
descriptor *and* the rogue child is killed.

The allocations are guaranteed to be *accounted* to the process which
created the VM, but only because KVM's per-{VM,vCPU} ioctls reject the
ioctl() with -EIO if kvm->mm != current->mm.  I.e. the child can keep
the VM "alive" but can't do anything useful with its reference.

Note that because 'struct kvm' also holds a reference to the mm_struct
of its owner, the above behavior also applies to userspace allocations.

Given that mucking with a VM's file descriptor can lead to subtle and
undesirable behavior, e.g. memcg charges persisting after a VM is shut
down, explicitly document a VM's lifecycle and its impact on the VM's
resources.

Alternatively, KVM could aggressively free resources when the creating
process exits, e.g. via mmu_notifier->release().  However, mmu_notifier
isn't guaranteed to be available, and freeing resources when the creator
exits is likely to be error prone and fragile as KVM would need to
ensure that it only freed resources that are truly out of reach. In
practice, the existing behavior shouldn't be problematic as a properly
configured system will prevent a child process from being moved out of
the appropriate cgroup hierarchy, i.e. prevent hiding the process from
the OOM killer, and will prevent an unprivileged user from being able to
to hold a reference to struct kvm via another method, e.g. debugfs.

[1]https://patchwork.kernel.org/patch/10806707/Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virtual/kvm/api.txt states:

  NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and
        KVM_EXIT_EPR the corresponding operations are complete (and guest
        state is consistent) only after userspace has re-entered the
        kernel with KVM_RUN.  The kernel side will first finish incomplete
        operations and then check for pending signals.  Userspace can
        re-enter the guest with an unmasked signal pending to complete
        pending operations.

Because guest state may be inconsistent, starting state migration after
an IO exit without first completing IO may result in test failures, e.g.
a proposed change to KVM's handling of %rip in its fast PIO handling[1]
will cause the new VM, i.e. the post-migration VM, to have its %rip set
to the IN instruction that triggered KVM_EXIT_IO, leading to a test
assertion due to a stage mismatch.

For simplicitly, require KVM_CAP_IMMEDIATE_EXIT to complete IO and skip
the test if it's not available.  The addition of KVM_CAP_IMMEDIATE_EXIT
predates the state selftest by more than a year.

[1] https://patchwork.kernel.org/patch/10848545/

Fixes: fa3899ad ("kvm: selftests: add basic test for state save and restore")
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Since 4.8.3, gcc has enabled -fstack-protector by default.  This is
problematic for the KVM selftests as they do not configure fs or gs
segments (the stack canary is pulled from fs:0x28).  With the default
behavior, gcc will insert a stack canary on any function that creates
buffers of 8 bytes or more.  As a result, ucall() will hit a triple
fault shutdown due to reading a bad fs segment when inserting its
stack canary, i.e. every test fails with an unexpected SHUTDOWN.

Fixes: 14c47b75 ("kvm: selftests: introduce ucall")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

KVM selftests embed the guest "image" as a function in the test itself
and extract the guest code at runtime by manually parsing the elf
headers.  The parsing is very simple and doesn't supporting fancy things
like position independent executables.  Recent versions of gcc enable
pie by default, which results in triple fault shutdowns in the guest due
to the virtual address in the headers not matching up with the virtual
address retrieved from the function pointer.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...so that the test doesn't end up in an infinite loop if it fails for
whatever reason, e.g. SHUTDOWN due to gcc inserting stack canary code
into ucall() and attempting to derefence a null segment.

Fixes: ca359066 ("kvm: selftests: add cr4_cpuid_sync_test")
Cc: Wei Huang <wei@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Most (all?) x86 platforms provide a port IO based reset mechanism, e.g.
OUT 92h or CF9h.  Userspace may emulate said mechanism, i.e. reset a
vCPU in response to KVM_EXIT_IO, without explicitly announcing to KVM
that it is doing a reset, e.g. Qemu jams vCPU state and resumes running.

To avoid corruping %rip after such a reset, commit 0967b7bf ("KVM:
Skip pio instruction when it is emulated, not executed") changed the
behavior of PIO handlers, i.e. today's "fast" PIO handling to skip the
instruction prior to exiting to userspace.  Full emulation doesn't need
such tricks becase re-emulating the instruction will naturally handle
%rip being changed to point at the reset vector.

Updating %rip prior to executing to userspace has several drawbacks:

  - Userspace sees the wrong %rip on the exit, e.g. if PIO emulation
    fails it will likely yell about the wrong address.
  - Single step exits to userspace for are effectively dropped as
    KVM_EXIT_DEBUG is overwritten with KVM_EXIT_IO.
  - Behavior of PIO emulation is different depending on whether it
    goes down the fast path or the slow path.

Rather than skip the PIO instruction before exiting to userspace,
snapshot the linear %rip and cancel PIO completion if the current
value does not match the snapshot.  For a 64-bit vCPU, i.e. the most
common scenario, the snapshot and comparison has negligible overhead
as VMCS.GUEST_RIP will be cached regardless, i.e. there is no extra
VMREAD in this case.

All other alternatives to snapshotting the linear %rip that don't
rely on an explicit reset announcenment suffer from one corner case
or another.  For example, canceling PIO completion on any write to
%rip fails if userspace does a save/restore of %rip, and attempting to
avoid that issue by canceling PIO only if %rip changed then fails if PIO
collides with the reset %rip.  Attempting to zero in on the exact reset
vector won't work for APs, which means adding more hooks such as the
vCPU's MP_STATE, and so on and so forth.

Checking for a linear %rip match technically suffers from corner cases,
e.g. userspace could theoretically rewrite the underlying code page and
expect a different instruction to execute, or the guest hardcodes a PIO
reset at 0xfffffff0, but those are far, far outside of what can be
considered normal operation.

Fixes: 432baf60 ("KVM: VMX: use kvm_fast_pio_in for handling IN I/O")
Cc: <stable@vger.kernel.org>
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

When userspace initializes guest vCPUs it may want to zero all supported
MSRs including Hyper-V related ones including HV_X64_MSR_STIMERn_CONFIG/
HV_X64_MSR_STIMERn_COUNT. With commit f3b138c5 ("kvm/x86: Update SynIC
timers on guest entry only") we began doing stimer_mark_pending()
unconditionally on every config change.

The issue I'm observing manifests itself as following:
- Qemu writes 0 to STIMERn_{CONFIG,COUNT} MSRs and marks all stimers as
  pending in stimer_pending_bitmap, arms KVM_REQ_HV_STIMER;
- kvm_hv_has_stimer_pending() starts returning true;
- kvm_vcpu_has_events() starts returning true;
- kvm_arch_vcpu_runnable() starts returning true;
- when kvm_arch_vcpu_ioctl_run() gets into
  (vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED) case:
  - kvm_vcpu_block() gets in 'kvm_vcpu_check_block(vcpu) < 0' and returns
    immediately, avoiding normal wait path;
  - -EAGAIN is returned from kvm_arch_vcpu_ioctl_run() immediately forcing
    userspace to retry.

So instead of normal wait path we get a busy loop on all secondary vCPUs
before they get INIT signal. This seems to be undesirable, especially given
that this happens even when Hyper-V extensions are not used.

Generally, it seems to be pointless to mark an stimer as pending in
stimer_pending_bitmap and arm KVM_REQ_HV_STIMER as the only thing
kvm_hv_process_stimers() will do is clear the corresponding bit. We may
just not mark disabled timers as pending instead.

Fixes: f3b138c5 ("kvm/x86: Update SynIC timers on guest entry only")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>