- 13 May, 2020 29 commits
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Davidlohr Bueso authored
The use of any sort of waitqueue (simple or regular) for wait/waking vcpus has always been an overkill and semantically wrong. Because this is per-vcpu (which is blocked) there is only ever a single waiting vcpu, thus no need for any sort of queue. As such, make use of the rcuwait primitive, with the following considerations: - rcuwait already provides the proper barriers that serialize concurrent waiter and waker. - Task wakeup is done in rcu read critical region, with a stable task pointer. - Because there is no concurrency among waiters, we need not worry about rcuwait_wait_event() calls corrupting the wait->task. As a consequence, this saves the locking done in swait when modifying the queue. This also applies to per-vcore wait for powerpc kvm-hv. The x86 tscdeadline_latency test mentioned in 8577370f ("KVM: Use simple waitqueue for vcpu->wq") shows that, on avg, latency is reduced by around 15-20% with this change. Cc: Paul Mackerras <paulus@ozlabs.org> Cc: kvmarm@lists.cs.columbia.edu Cc: linux-mips@vger.kernel.org Reviewed-by:
Marc Zyngier <maz@kernel.org> Signed-off-by:
Davidlohr Bueso <dbueso@suse.de> Message-Id: <20200424054837.5138-6-dave@stgolabs.net> [Avoid extra logic changes. - Paolo] Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Davidlohr Bueso authored
This call is lockless and thus should not be trusted blindly. For example, the return value of rcuwait_wakeup() should be used to track whether a process was woken up. Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by:
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Davidlohr Bueso authored
This allows further flexibility for some callers to implement ad-hoc versions of the generic rcuwait_wait_event(). For example, kvm will need this to maintain tracing semantics. The naming is of course similar to what waitqueue apis offer. Also go ahead and make use of rcu_assign_pointer() for both task writes as it will make the __rcu sparse people happy - this will be the special nil case, thus no added serialization. Acked-by:
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Davidlohr Bueso authored
Propagating the return value of wake_up_process() back to the caller can come in handy for future users, such as for statistics or accounting purposes. Acked-by:
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Davidlohr Bueso authored
The 'trywake' name was renamed to simply 'wake', update the comment. Acked-by:
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Paolo Bonzini authored
Add an argument to interrupt_allowed and nmi_allowed, to checking if interrupt injection is blocked. Use the hook to handle the case where an interrupt arrives between check_nested_events() and the injection logic. Drop the retry of check_nested_events() that hack-a-fixed the same condition. Blocking injection is also a bit of a hack, e.g. KVM should do exiting and non-exiting interrupt processing in a single pass, but it's a more precise hack. The old comment is also misleading, e.g. KVM_REQ_EVENT is purely an optimization, setting it on every run loop (which KVM doesn't do) should not affect functionality, only performance. Signed-off-by:
Sean Christopherson <sean.j.christopherson@intel.com> Message-Id: <20200423022550.15113-13-sean.j.christopherson@intel.com> [Extend to SVM, add SMI and NMI. Even though NMI and SMI cannot come asynchronously right now, making the fix generic is easy and removes a special case. - Paolo] Signed-off-by:
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Sean Christopherson authored
Use vmx_get_rflags() instead of manually reading vmcs.GUEST_RFLAGS when querying RFLAGS.IF so that multiple checks against interrupt blocking in a single run loop only require a single VMREAD. Signed-off-by:
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Sean Christopherson authored
Use vmx_interrupt_blocked() instead of bouncing through vmx_interrupt_allowed() when handling edge cases in vmx_handle_exit(). The nested_run_pending check in vmx_interrupt_allowed() should never evaluate true in the VM-Exit path. Hoist the WARN in handle_invalid_guest_state() up to vmx_handle_exit() to enforce the above assumption for the !enable_vnmi case, and to detect any other potential bugs with nested VM-Enter. Signed-off-by:
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Sean Christopherson authored
WARN if a pending exception is coincident with an injected exception before calling check_nested_events() so that the WARN will fire even if inject_pending_event() bails early because check_nested_events() detects the conflict. Bailing early isn't problematic (quite the opposite), but suppressing the WARN is undesirable as it could mask a bug elsewhere in KVM. Signed-off-by:
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Paolo Bonzini authored
Short circuit vmx_check_nested_events() if an unblocked IRQ/NMI/SMI is pending and needs to be injected into L2, priority between coincident events is not dependent on exiting behavior. Fixes: b518ba9f ("KVM: nSVM: implement check_nested_events for interrupts") Signed-off-by:
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Paolo Bonzini authored
Report interrupts as allowed when the vCPU is in L2 and L2 is being run with exit-on-interrupts enabled and EFLAGS.IF=1 (either on the host or on the guest according to VINTR). Interrupts are always unblocked from L1's perspective in this case. While moving nested_exit_on_intr to svm.h, use INTERCEPT_INTR properly instead of assuming it's zero (which it is of course). Signed-off-by: -
Sean Christopherson authored
Check for an unblocked SMI in vmx_check_nested_events() so that pending SMIs are correctly prioritized over IRQs and NMIs when the latter events will trigger VM-Exit. This also fixes an issue where an SMI that was marked pending while processing a nested VM-Enter wouldn't trigger an immediate exit, i.e. would be incorrectly delayed until L2 happened to take a VM-Exit. Fixes: 64d60670 ("KVM: x86: stubs for SMM support") Signed-off-by:
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Sean Christopherson authored
Short circuit vmx_check_nested_events() if an unblocked IRQ/NMI is pending and needs to be injected into L2, priority between coincident events is not dependent on exiting behavior. Fixes: b6b8a145 ("KVM: nVMX: Rework interception of IRQs and NMIs") Signed-off-by:
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Paolo Bonzini authored
Move the architectural (non-KVM specific) interrupt/NMI/SMI blocking checks to a separate helper so that they can be used in a future patch by svm_check_nested_events(). No functional change intended. Signed-off-by: -
Sean Christopherson authored
Move the architectural (non-KVM specific) interrupt/NMI blocking checks to a separate helper so that they can be used in a future patch by vmx_check_nested_events(). No functional change intended. Signed-off-by:
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Paolo Bonzini authored
Unlike VMX, SVM allows a hypervisor to take a SMI vmexit without having any special SMM-monitor enablement sequence. Therefore, it has to be handled like interrupts and NMIs. Check for an unblocked SMI in svm_check_nested_events() so that pending SMIs are correctly prioritized over IRQs and NMIs when the latter events will trigger VM-Exit. Note that there is no need to test explicitly for SMI vmexits, because guests always runs outside SMM and therefore can never get an SMI while they are blocked. Signed-off-by: -
Paolo Bonzini authored
Report NMIs as allowed when the vCPU is in L2 and L2 is being run with Exit-on-NMI enabled, as NMIs are always unblocked from L1's perspective in this case. Signed-off-by: -
Sean Christopherson authored
Report NMIs as allowed when the vCPU is in L2 and L2 is being run with Exit-on-NMI enabled, as NMIs are always unblocked from L1's perspective in this case. Signed-off-by:
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Paolo Bonzini authored
Do not hardcode is_smm so that all the architectural conditions for blocking SMIs are listed in a single place. Well, in two places because this introduces some code duplication between Intel and AMD. This ensures that nested SVM obeys GIF in kvm_vcpu_has_events. Signed-off-by: -
Sean Christopherson authored
Return an actual bool for kvm_x86_ops' {interrupt_nmi}_allowed() hook to better reflect the return semantics, and to avoid creating an even bigger mess when the related VMX code is refactored in upcoming patches. Signed-off-by: -
Sean Christopherson authored
Re-request KVM_REQ_EVENT if vcpu_enter_guest() bails after processing pending requests and an immediate exit was requested. This fixes a bug where a pending event, e.g. VMX preemption timer, is delayed and/or lost if the exit was deferred due to something other than a higher priority _injected_ event, e.g. due to a pending nested VM-Enter. This bug only affects the !injected case as kvm_x86_ops.cancel_injection() sets KVM_REQ_EVENT to redo the injection, but that's purely serendipitous behavior with respect to the deferred event. Note, emulated preemption timer isn't the only event that can be affected, it simply happens to be the only event where not re-requesting KVM_REQ_EVENT is blatantly visible to the guest. Fixes: f4124500 ("KVM: nVMX: Fully emulate preemption timer") Signed-off-by:
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Sean Christopherson authored
Add a kvm_x86_ops hook to detect a nested pending "hypervisor timer" and use it to effectively open a window for servicing the expired timer. Like pending SMIs on VMX, opening a window simply means requesting an immediate exit. This fixes a bug where an expired VMX preemption timer (for L2) will be delayed and/or lost if a pending exception is injected into L2. The pending exception is rightly prioritized by vmx_check_nested_events() and injected into L2, with the preemption timer left pending. Because no window opened, L2 is free to run uninterrupted. Fixes: f4124500 ("KVM: nVMX: Fully emulate preemption timer") Reported-by:
Jim Mattson <jmattson@google.com> Cc: Oliver Upton <oupton@google.com> Cc: Peter Shier <pshier@google.com> Signed-off-by:
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Sean Christopherson authored
Short circuit vmx_check_nested_events() if an exception is pending and needs to be injected into L2, priority between coincident events is not dependent on exiting behavior. This fixes a bug where a single-step #DB that is not intercepted by L1 is incorrectly dropped due to servicing a VMX Preemption Timer VM-Exit. Injected exceptions also need to be blocked if nested VM-Enter is pending or an exception was already injected, otherwise injecting the exception could overwrite an existing event injection from L1. Technically, this scenario should be impossible, i.e. KVM shouldn't inject its own exception during nested VM-Enter. This will be addressed in a future patch. Note, event priority between SMI, NMI and INTR is incorrect for L2, e.g. SMI should take priority over VM-Exit on NMI/INTR, and NMI that is injected into L2 should take priority over VM-Exit INTR. This will also be addressed in a future patch. Fixes: b6b8a145 ("KVM: nVMX: Rework interception of IRQs and NMIs") Reported-by:
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Cathy Avery authored
Migrate nested guest NMI intercept processing to new check_nested_events. Signed-off-by:
Cathy Avery <cavery@redhat.com> Message-Id: <20200414201107.22952-2-cavery@redhat.com> [Reorder clauses as NMIs have higher priority than IRQs; inject immediate vmexit as is now done for IRQ vmexits. - Paolo] Signed-off-by:
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Paolo Bonzini authored
We can immediately leave SVM guest mode in svm_check_nested_events now that we have the nested_run_pending mechanism. This makes things easier because we can run the rest of inject_pending_event with GIF=0, and KVM will naturally end up requesting the next interrupt window. Signed-off-by: -
Paolo Bonzini authored
Similar to VMX, we need to leave the halted state when performing a vmexit. Failure to do so will cause a hang after vmexit. Signed-off-by: -
Paolo Bonzini authored
We want to inject vmexits immediately from svm_check_nested_events, so that the interrupt/NMI window requests happen in inject_pending_event right after it returns. This however has the same issue as in vmx_check_nested_events, so introduce a nested_run_pending flag with the exact same purpose of delaying vmexit injection after the vmentry. Signed-off-by: -
Paolo Bonzini authored
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Babu Moger authored
Though rdpkru and wrpkru are contingent upon CR4.PKE, the PKRU resource isn't. It can be read with XSAVE and written with XRSTOR. So, if we don't set the guest PKRU value here(kvm_load_guest_xsave_state), the guest can read the host value. In case of kvm_load_host_xsave_state, guest with CR4.PKE clear could potentially use XRSTOR to change the host PKRU value. While at it, move pkru state save/restore to common code and the host_pkru field to kvm_vcpu_arch. This will let SVM support protection keys. Cc: stable@vger.kernel.org Reported-by:
Babu Moger <babu.moger@amd.com> Message-Id: <158932794619.44260.14508381096663848853.stgit@naples-babu.amd.com> Signed-off-by:
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- 08 May, 2020 5 commits
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Suravee Suthikulpanit authored
The commit 64b5bd27 ("KVM: nSVM: ignore L1 interrupt window while running L2 with V_INTR_MASKING=1") introduced a WARN_ON, which checks if AVIC is enabled when trying to set V_IRQ in the VMCB for enabling irq window. The following warning is triggered because the requesting vcpu (to deactivate AVIC) does not get to process APICv update request for itself until the next #vmexit. WARNING: CPU: 0 PID: 118232 at arch/x86/kvm/svm/svm.c:1372 enable_irq_window+0x6a/0xa0 [kvm_amd] RIP: 0010:enable_irq_window+0x6a/0xa0 [kvm_amd] Call Trace: kvm_arch_vcpu_ioctl_run+0x6e3/0x1b50 [kvm] ? kvm_vm_ioctl_irq_line+0x27/0x40 [kvm] ? _copy_to_user+0x26/0x30 ? kvm_vm_ioctl+0xb3e/0xd90 [kvm] ? set_next_entity+0x78/0xc0 kvm_vcpu_ioctl+0x236/0x610 [kvm] ksys_ioctl+0x8a/0xc0 __x64_sys_ioctl+0x1a/0x20 do_syscall_64+0x58/0x210 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes by sending APICV update request to all other vcpus, and immediately update APIC for itself. Signed-off-by:
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> Link: https://lkml.org/lkml/2020/5/2/167 Fixes: 64b5bd27 ("KVM: nSVM: ignore L1 interrupt window while running L2 with V_INTR_MASKING=1") Message-Id: <1588818939-54264-1-git-send-email-suravee.suthikulpanit@amd.com> Signed-off-by:
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Suravee Suthikulpanit authored
This allows making request to all other vcpus except the one specified in the parameter. Signed-off-by:
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Paolo Bonzini authored
When KVM_EXIT_DEBUG is raised for the disabled-breakpoints case (DR7.GD), DR6 was incorrectly copied from the value in the VM. Instead, DR6.BD should be set in order to catch this case. On AMD this does not need any special code because the processor triggers a #DB exception that is intercepted. However, the testcase would fail without the previous patch because both DR6.BS and DR6.BD would be set. Signed-off-by: -
Paolo Bonzini authored
There are two issues with KVM_EXIT_DEBUG on AMD, whose root cause is the different handling of DR6 on intercepted #DB exceptions on Intel and AMD. On Intel, #DB exceptions transmit the DR6 value via the exit qualification field of the VMCS, and the exit qualification only contains the description of the precise event that caused a vmexit. On AMD, instead the DR6 field of the VMCB is filled in as if the #DB exception was to be injected into the guest. This has two effects when guest debugging is in use: * the guest DR6 is clobbered * the kvm_run->debug.arch.dr6 field can accumulate more debug events, rather than just the last one that happened (the testcase in the next patch covers this issue). This patch fixes both issues by emulating, so to speak, the Intel behavior on AMD processors. The important observation is that (after the previous patches) the VMCB value of DR6 is only ever observable from the guest is KVM_DEBUGREG_WONT_EXIT is set. Therefore we can actually set vmcb->save.dr6 to any value we want as long as KVM_DEBUGREG_WONT_EXIT is clear, which it will be if guest debugging is enabled. Therefore it is possible to enter the guest with an all-zero DR6, reconstruct the #DB payload from the DR6 we get at exit time, and let kvm_deliver_exception_payload move the newly set bits into vcpu->arch.dr6. Some extra bits may be included in the payload if KVM_DEBUGREG_WONT_EXIT is set, but this is harmless. This may not be the most optimized way to deal with this, but it is simple and, being confined within SVM code, it gets rid of the set_dr6 callback and kvm_update_dr6. Signed-off-by: -
Paolo Bonzini authored
kvm_x86_ops.set_dr6 is only ever called with vcpu->arch.dr6 as the second argument. Ensure that the VMCB value is synchronized to vcpu->arch.dr6 on #DB (both "normal" and nested) and nested vmentry, so that the current value of DR6 is always available in vcpu->arch.dr6. The get_dr6 callback can just access vcpu->arch.dr6 and becomes redundant. Signed-off-by:
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- 07 May, 2020 6 commits
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Paolo Bonzini authored
Signed-off-by: -
Peter Xu authored
Covers fundamental tests for KVM_SET_GUEST_DEBUG. It is very close to the debug test in kvm-unit-test, but doing it from outside the guest. Signed-off-by:
Peter Xu <peterx@redhat.com> Message-Id: <20200505205000.188252-4-peterx@redhat.com> Signed-off-by:
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Peter Xu authored
When single-step triggered with KVM_SET_GUEST_DEBUG, we should fill in the pc value with current linear RIP rather than the cached singlestep address. Signed-off-by:
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Peter Xu authored
RTM should always been set even with KVM_EXIT_DEBUG on #DB. Signed-off-by:
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Paolo Bonzini authored
Go through kvm_queue_exception_p so that the payload is correctly delivered through the exit qualification, and add a kvm_update_dr6 call to kvm_deliver_exception_payload that is needed on AMD. Reported-by:
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Peter Xu authored
KVM_CAP_SET_GUEST_DEBUG should be supported for x86 however it's not declared as supported. My wild guess is that userspaces like QEMU are using "#ifdef KVM_CAP_SET_GUEST_DEBUG" to check for the capability instead, but that could be wrong because the compilation host may not be the runtime host. The userspace might still want to keep the old "#ifdef" though to not break the guest debug on old kernels. Signed-off-by:
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