- 29 Dec, 2022 40 commits
-
-
Chao Gao authored
Disable CPU hotplug when enabling/disabling hardware to prevent the corner case where if the following sequence occurs: 1. A hotplugged CPU marks itself online in cpu_online_mask 2. The hotplugged CPU enables interrupt before invoking KVM's ONLINE callback 3 hardware_{en,dis}able_all() is invoked on another CPU the hotplugged CPU will be included in on_each_cpu() and thus get sent through hardware_{en,dis}able_nolock() before kvm_online_cpu() is called. start_secondary { ... set_cpu_online(smp_processor_id(), true); <- 1 ... local_irq_enable(); <- 2 ... cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); <- 3 } KVM currently fudges around this race by keeping track of which CPUs have done hardware enabling (see commit 1b6c0168 "KVM: Keep track of which cpus have virtualization enabled"), but that's an inefficient, convoluted, and hacky solution. Signed-off-by:Chao Gao <chao.gao@intel.com> [sean: split to separate patch, write changelog] Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20221130230934.1014142-43-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
-
Chao Gao authored
The CPU STARTING section doesn't allow callbacks to fail. Move KVM's hotplug callback to ONLINE section so that it can abort onlining a CPU in certain cases to avoid potentially breaking VMs running on existing CPUs. For example, when KVM fails to enable hardware virtualization on the hotplugged CPU. Place KVM's hotplug state before CPUHP_AP_SCHED_WAIT_EMPTY as it ensures when offlining a CPU, all user tasks and non-pinned kernel tasks have left the CPU, i.e. there cannot be a vCPU task around. So, it is safe for KVM's CPU offline callback to disable hardware virtualization at that point. Likewise, KVM's online callback can enable hardware virtualization before any vCPU task gets a chance to run on hotplugged CPUs. Drop kvm_x86_check_processor_compatibility()'s WARN that IRQs are disabled, as the ONLINE section runs with IRQs disabled. The WARN wasn't intended to be a requirement, e.g. disabling preemption is sufficient, the IRQ thing was purely an aggressive sanity check since the helper was only ever invoked via SMP function call. Rename KVM's CPU hotplug callbacks accordingly. Suggested-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Isaku Yamahata <isaku.yamahata@intel.com> Reviewed-by:
Yuan Yao <yuan.yao@intel.com> [sean: drop WARN that IRQs are disabled] Signed-off-by:
-
Chao Gao authored
Do compatibility checks when enabling hardware to effectively add compatibility checks when onlining a CPU. Abort enabling, i.e. the online process, if the (hotplugged) CPU is incompatible with the known good setup. At init time, KVM does compatibility checks to ensure that all online CPUs support hardware virtualization and a common set of features. But KVM uses hotplugged CPUs without such compatibility checks. On Intel CPUs, this leads to #GP if the hotplugged CPU doesn't support VMX, or VM-Entry failure if the hotplugged CPU doesn't support all features enabled by KVM. Note, this is little more than a NOP on SVM, as SVM already checks for full SVM support during hardware enabling. Opportunistically add a pr_err() if setup_vmcs_config() fails, and tweak all error messages to output which CPU failed. Signed-off-by:
Kai Huang <kai.huang@intel.com> Message-Id: <20221130230934.1014142-41-seanjc@google.com> Signed-off-by:
-
Sean Christopherson authored
Move the .check_processor_compatibility() callback from kvm_x86_init_ops to kvm_x86_ops to allow a future patch to do compatibility checks during CPU hotplug. Do kvm_ops_update() before compat checks so that static_call() can be used during compat checks. Signed-off-by:
-
Sean Christopherson authored
Check that SVM is supported and enabled in the processor compatibility checks. SVM already checks for support during hardware enabling, i.e. this doesn't really add new functionality. The net effect is that KVM will refuse to load if a CPU doesn't have SVM fully enabled, as opposed to failing KVM_CREATE_VM. Opportunistically move svm_check_processor_compat() up in svm.c so that it can be invoked during hardware enabling in a future patch. Signed-off-by:
-
Sean Christopherson authored
Reorder code in vmx.c so that the VMX support check helpers reside above the hardware enabling helpers, which will allow KVM to perform support checks during hardware enabling (in a future patch). No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Do basic VMX/SVM support checks directly in vendor code instead of implementing them via kvm_x86_ops hooks. Beyond the superficial benefit of providing common messages, which isn't even clearly a net positive since vendor code can provide more precise/detailed messages, there's zero advantage to bouncing through common x86 code. Consolidating the checks will also simplify performing the checks across all CPUs (in a future patch). Signed-off-by:
-
Sean Christopherson authored
Use this_cpu_has() instead of boot_cpu_has() to perform the effective "disabled by BIOS?" checks for VMX. This will allow consolidating code between vmx_disabled_by_bios() and vmx_check_processor_compat(). Checking the boot CPU isn't a strict requirement as any divergence in VMX enabling between the boot CPU and other CPUs will result in KVM refusing to load thanks to the aforementioned vmx_check_processor_compat(). Furthermore, using the boot CPU was an unintentional change introduced by commit a4d0b2fd ("KVM: VMX: Use VMX feature flag to query BIOS enabling"). Prior to using the feature flags, KVM checked the raw MSR value from the current CPU. Reported-by:
-
Sean Christopherson authored
Define pr_fmt using KBUILD_MODNAME for all KVM x86 code so that printks use consistent formatting across common x86, Intel, and AMD code. In addition to providing consistent print formatting, using KBUILD_MODNAME, e.g. kvm_amd and kvm_intel, allows referencing SVM and VMX (and SEV and SGX and ...) as technologies without generating weird messages, and without causing naming conflicts with other kernel code, e.g. "SEV: ", "tdx: ", "sgx: " etc.. are all used by the kernel for non-KVM subsystems. Opportunistically move away from printk() for prints that need to be modified anyways, e.g. to drop a manual "kvm: " prefix. Opportunistically convert a few SGX WARNs that are similarly modified to WARN_ONCE; in the very unlikely event that the WARNs fire, odds are good that they would fire repeatedly and spam the kernel log without providing unique information in each print. Note, defining pr_fmt yields undesirable results for code that uses KVM's printk wrappers, e.g. vcpu_unimpl(). But, that's a pre-existing problem as SVM/kvm_amd already defines a pr_fmt, and thankfully use of KVM's wrappers is relatively limited in KVM x86 code. Signed-off-by:
Paul Durrant <paul@xen.org> Message-Id: <20221130230934.1014142-35-seanjc@google.com> Signed-off-by:
-
Sean Christopherson authored
Use KBUILD_MODNAME to specify the vendor module name instead of manually writing out the name to make it a bit more obvious that the name isn't completely arbitrary. A future patch will also use KBUILD_MODNAME to define pr_fmt, at which point using KBUILD_MODNAME for kvm_x86_ops.name further reinforces the intended usage of kvm_x86_ops.name. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Drop kvm_arch_check_processor_compat() and its support code now that all architecture implementations are nops. Signed-off-by:
Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Eric Farman <farman@linux.ibm.com> # s390 Acked-by:
Anup Patel <anup@brainfault.org> Reviewed-by:
-
Sean Christopherson authored
Move the CPU compatibility checks to pure x86 code, i.e. drop x86's use of the common kvm_x86_check_cpu_compat() arch hook. x86 is the only architecture that "needs" to do per-CPU compatibility checks, moving the logic to x86 will allow dropping the common code, and will also give x86 more control over when/how the compatibility checks are performed, e.g. TDX will need to enable hardware (do VMXON) in order to perform compatibility checks. Signed-off-by:
-
Sean Christopherson authored
Tag vmcs_config and vmx_capability structs as __init, the canonical configuration is generated during hardware_setup() and must never be modified after that point. Signed-off-by:
-
Sean Christopherson authored
Drop kvm_arch_init() and kvm_arch_exit() now that all implementations are nops. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Tag __kvm_s390_init() and its unique helpers as __init. These functions are only ever called during module_init(), but could not be tagged accordingly while they were invoked from the common kvm_arch_init(), which is not __init because of x86. Signed-off-by:
Eric Farman <farman@linux.ibm.com> Message-Id: <20221130230934.1014142-29-seanjc@google.com> Signed-off-by:
-
Sean Christopherson authored
Move the guts of kvm_arch_init() into a new helper, __kvm_s390_init(), and invoke the new helper directly from kvm_s390_init() instead of bouncing through kvm_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), i.e. this is a glorified nop. Moving setup to __kvm_s390_init() will allow tagging more functions as __init, and emptying kvm_arch_init() will allow dropping the hook entirely once all architecture implementations are nops. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Move KVM PPC's compatibility checks to their respective module_init() hooks, there's no need to wait until KVM's common compat check, nor is there a need to perform the check on every CPU (provided by common KVM's hook), as the compatibility checks operate on global data. arch/powerpc/include/asm/cputable.h: extern struct cpu_spec *cur_cpu_spec; arch/powerpc/kvm/book3s.c: return 0 arch/powerpc/kvm/e500.c: strcmp(cur_cpu_spec->cpu_name, "e500v2") arch/powerpc/kvm/e500mc.c: strcmp(cur_cpu_spec->cpu_name, "e500mc") strcmp(cur_cpu_spec->cpu_name, "e5500") strcmp(cur_cpu_spec->cpu_name, "e6500") Cc: Fabiano Rosas <farosas@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: -
Sean Christopherson authored
Now that KVM setup is handled directly in riscv_kvm_init(), tag functions and data that are used/set only during init with __init/__ro_after_init. Signed-off-by:
-
Sean Christopherson authored
Fold the guts of kvm_arch_init() into riscv_kvm_init() instead of bouncing through kvm_init()=>kvm_arch_init(). Functionally, this is a glorified nop as invoking kvm_arch_init() is the very first action performed by kvm_init(). Moving setup to riscv_kvm_init(), which is tagged __init, will allow tagging more functions and data with __init and __ro_after_init. And emptying kvm_arch_init() will allow dropping the hook entirely once all architecture implementations are nops. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Call kvm_init() only after _all_ setup is complete, as kvm_init() exposes /dev/kvm to userspace and thus allows userspace to create VMs (and call other ioctls). Signed-off-by:
-
Sean Christopherson authored
Invoke kvm_mips_emulation_init() directly from kvm_mips_init() instead of bouncing through kvm_init()=>kvm_arch_init(). Functionally, this is a glorified nop as invoking kvm_arch_init() is the very first action performed by kvm_init(). Emptying kvm_arch_init() will allow dropping the hook entirely once all architecture implementations are nops. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Now that KVM no longer supports trap-and-emulate (see commit 45c7e8af "MIPS: Remove KVM_TE support"), hardcode the MIPS callbacks to the virtualization callbacks. Harcoding the callbacks eliminates the technically-unnecessary check on non-NULL kvm_mips_callbacks in kvm_arch_init(). MIPS has never supported multiple in-tree modules, i.e. barring an out-of-tree module, where copying and renaming kvm.ko counts as "out-of-tree", KVM could never encounter a non-NULL set of callbacks during module init. The callback check is also subtly broken, as it is not thread safe, i.e. if there were multiple modules, loading both concurrently would create a race between checking and setting kvm_mips_callbacks. Given that out-of-tree shenanigans are not the kernel's responsibility, hardcode the callbacks to simplify the code. Signed-off-by:
-
Sean Christopherson authored
Tag kvm_arm_init() and its unique helper as __init, and tag data that is only ever modified under the kvm_arm_init() umbrella as read-only after init. Opportunistically name the boolean param in kvm_timer_hyp_init()'s prototype to match its definition. Signed-off-by:
-
Sean Christopherson authored
Do arm/arch specific initialization directly in arm's module_init(), now called kvm_arm_init(), instead of bouncing through kvm_init() to reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), so from a initialization perspective this is a glorified nop. Avoiding kvm_arch_init() also fixes a mostly benign bug as kvm_arch_exit() doesn't properly unwind if a later stage of kvm_init() fails. While the soon-to-be-deleted comment about compiling as a module being unsupported is correct, kvm_arch_exit() can still be called by kvm_init() if any step after the call to kvm_arch_init() succeeds. Add a FIXME to call out that pKVM initialization isn't unwound if kvm_init() fails, which is a pre-existing problem inherited from kvm_arch_exit(). Making kvm_arch_init() a nop will also allow dropping kvm_arch_init() and kvm_arch_exit() entirely once all other architectures follow suit. Signed-off-by:
-
Sean Christopherson authored
Undo everything done by init_subsystems() if a later initialization step fails, i.e. unregister perf callbacks in addition to unregistering the power management notifier. Fixes: bfa79a80 ("KVM: arm64: Elevate hypervisor mappings creation at EL2") Signed-off-by:
-
Sean Christopherson authored
Teardown hypervisor mode if vector slot setup fails in order to avoid leaking any allocations done by init_hyp_mode(). Fixes: b881cdce ("KVM: arm64: Allocate hyp vectors statically") Signed-off-by:
-
Marc Zyngier authored
For a number of historical reasons, the KVM/arm64 hotplug setup is pretty complicated, and we have two extra CPUHP notifiers for vGIC and timers. It looks pretty pointless, and gets in the way of further changes. So let's just expose some helpers that can be called from the core CPUHP callback, and get rid of everything else. This gives us the opportunity to drop a useless notifier entry, as well as tidy-up the timer enable/disable, which was a bit odd. Signed-off-by:
Marc Zyngier <maz@kernel.org> Signed-off-by:
-
Sean Christopherson authored
Acquire a new mutex, vendor_module_lock, in kvm_x86_vendor_init() while doing hardware setup to ensure that concurrent calls are fully serialized. KVM rejects attempts to load vendor modules if a different module has already been loaded, but doesn't handle the case where multiple vendor modules are loaded at the same time, and module_init() doesn't run under the global module_mutex. Note, in practice, this is likely a benign bug as no platform exists that supports both SVM and VMX, i.e. barring a weird VM setup, one of the vendor modules is guaranteed to fail a support check before modifying common KVM state. Alternatively, KVM could perform an atomic CMPXCHG on .hardware_enable, but that comes with its own ugliness as it would require setting .hardware_enable before success is guaranteed, e.g. attempting to load the "wrong" could result in spurious failure to load the "right" module. Introduce a new mutex as using kvm_lock is extremely deadlock prone due to kvm_lock being taken under cpus_write_lock(), and in the future, under under cpus_read_lock(). Any operation that takes cpus_read_lock() while holding kvm_lock would potentially deadlock, e.g. kvm_timer_init() takes cpus_read_lock() to register a callback. In theory, KVM could avoid such problematic paths, i.e. do less setup under kvm_lock, but avoiding all calls to cpus_read_lock() is subtly difficult and thus fragile. E.g. updating static calls also acquires cpus_read_lock(). Inverting the lock ordering, i.e. always taking kvm_lock outside cpus_read_lock(), is not a viable option as kvm_lock is taken in various callbacks that may be invoked under cpus_read_lock(), e.g. x86's kvmclock_cpufreq_notifier(). The lockdep splat below is dependent on future patches to take cpus_read_lock() in hardware_enable_all(), but as above, deadlock is already is already possible. ====================================================== WARNING: possible circular locking dependency detected 6.0.0-smp--7ec93244f194-init2 #27 Tainted: G O ------------------------------------------------------ stable/251833 is trying to acquire lock: ffffffffc097ea28 (kvm_lock){+.+.}-{3:3}, at: hardware_enable_all+0x1f/0xc0 [kvm] but task is already holding lock: ffffffffa2456828 (cpu_hotplug_lock){++++}-{0:0}, at: hardware_enable_all+0xf/0xc0 [kvm] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (cpu_hotplug_lock){++++}-{0:0}: cpus_read_lock+0x2a/0xa0 __cpuhp_setup_state+0x2b/0x60 __kvm_x86_vendor_init+0x16a/0x1870 [kvm] kvm_x86_vendor_init+0x23/0x40 [kvm] 0xffffffffc0a4d02b do_one_initcall+0x110/0x200 do_init_module+0x4f/0x250 load_module+0x1730/0x18f0 __se_sys_finit_module+0xca/0x100 __x64_sys_finit_module+0x1d/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (kvm_lock){+.+.}-{3:3}: __lock_acquire+0x16f4/0x30d0 lock_acquire+0xb2/0x190 __mutex_lock+0x98/0x6f0 mutex_lock_nested+0x1b/0x20 hardware_enable_all+0x1f/0xc0 [kvm] kvm_dev_ioctl+0x45e/0x930 [kvm] __se_sys_ioctl+0x77/0xc0 __x64_sys_ioctl+0x1d/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(cpu_hotplug_lock); lock(kvm_lock); lock(cpu_hotplug_lock); lock(kvm_lock); *** DEADLOCK *** 1 lock held by stable/251833: #0: ffffffffa2456828 (cpu_hotplug_lock){++++}-{0:0}, at: hardware_enable_all+0xf/0xc0 [kvm] Signed-off-by: -
Sean Christopherson authored
Call kvm_init() only after _all_ setup is complete, as kvm_init() exposes /dev/kvm to userspace and thus allows userspace to create VMs (and call other ioctls). E.g. KVM will encounter a NULL pointer when attempting to add a vCPU to the per-CPU loaded_vmcss_on_cpu list if userspace is able to create a VM before vmx_init() configures said list. BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP CPU: 6 PID: 1143 Comm: stable Not tainted 6.0.0-rc7+ #988 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:vmx_vcpu_load_vmcs+0x68/0x230 [kvm_intel] <TASK> vmx_vcpu_load+0x16/0x60 [kvm_intel] kvm_arch_vcpu_load+0x32/0x1f0 [kvm] vcpu_load+0x2f/0x40 [kvm] kvm_arch_vcpu_create+0x231/0x310 [kvm] kvm_vm_ioctl+0x79f/0xe10 [kvm] ? handle_mm_fault+0xb1/0x220 __x64_sys_ioctl+0x80/0xb0 do_syscall_64+0x2b/0x50 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7f5a6b05743b </TASK> Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel(+) kvm irqbypass Cc: stable@vger.kernel.org Signed-off-by:
-
Sean Christopherson authored
Move the guts of kvm_arch_init() to a new helper, kvm_x86_vendor_init(), so that VMX can do _all_ arch and vendor initialization before calling kvm_init(). Calling kvm_init() must be the _very_ last step during init, as kvm_init() exposes /dev/kvm to userspace, i.e. allows creating VMs. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Move Hyper-V's eVMCS initialization to a dedicated helper to clean up vmx_init(), and add a comment to call out that the Hyper-V init code doesn't need to be unwound if vmx_init() ultimately fails. No functional change intended. Signed-off-by:
Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20221130230934.1014142-13-seanjc@google.com> Signed-off-by:
-
Sean Christopherson authored
Don't disable the eVMCS static key on module exit, kvm_intel.ko owns the key so there can't possibly be users after the kvm_intel.ko is unloaded, at least not without much bigger issues. Signed-off-by:
-
Sean Christopherson authored
Reset the eVMCS controls in the per-CPU VP assist page during hardware disabling instead of waiting until kvm-intel's module exit. The controls are activated if and only if KVM creates a VM, i.e. don't need to be reset if hardware is never enabled. Doing the reset during hardware disabling will naturally fix a potential NULL pointer deref bug once KVM disables CPU hotplug while enabling and disabling hardware (which is necessary to fix a variety of bugs). If the kernel is running as the root partition, the VP assist page is unmapped during CPU hot unplug, and so KVM's clearing of the eVMCS controls needs to occur with CPU hot(un)plug disabled, otherwise KVM could attempt to write to a CPU's VP assist page after it's unmapped. Reported-by:
-
Sean Christopherson authored
Drop kvm_arch_hardware_setup() and kvm_arch_hardware_unsetup() now that all implementations are nops. No functional change intended. Signed-off-by:
-
Sean Christopherson authored
Now that kvm_arch_hardware_setup() is called immediately after kvm_arch_init(), fold the guts of kvm_arch_hardware_(un)setup() into kvm_arch_{init,exit}() as a step towards dropping one of the hooks. To avoid having to unwind various setup, e.g registration of several notifiers, slot in the vendor hardware setup before the registration of said notifiers and callbacks. Introducing a functional change while moving code is less than ideal, but the alternative is adding a pile of unwinding code, which is much more error prone, e.g. several attempts to move the setup code verbatim all introduced bugs. Add a comment to document that kvm_ops_update() is effectively the point of no return, e.g. it sets the kvm_x86_ops.hardware_enable canary and so needs to be unwound. Signed-off-by: -
Sean Christopherson authored
Move kvm_arch_init()'s call to kvm_timer_init() down a few lines below the XCR0 configuration code. A future patch will move hardware setup into kvm_arch_init() and slot in vendor hardware setup before the call to kvm_timer_init() so that timer initialization (among other stuff) doesn't need to be unwound if vendor setup fails. XCR0 setup on the other hand needs to happen before vendor hardware setup. Signed-off-by:
-
Sean Christopherson authored
Now that kvm_arch_hardware_setup() is called immediately after kvm_arch_init(), fold the guts of kvm_arch_hardware_(un)setup() into kvm_arch_{init,exit}() as a step towards dropping one of the hooks. No functional change intended. Signed-off-by: -
Sean Christopherson authored
In preparation for folding kvm_arch_hardware_setup() into kvm_arch_init(), unwind initialization one step at a time instead of simply calling kvm_arch_exit(). Using kvm_arch_exit() regardless of which initialization step failed relies on all affected state playing nice with being undone even if said state wasn't first setup. That holds true for state that is currently configured by kvm_arch_init(), but not for state that's handled by kvm_arch_hardware_setup(), e.g. calling gmap_unregister_pte_notifier() without first registering a notifier would result in list corruption due to attempting to delete an entry that was never added to the list. Signed-off-by:
-
Sean Christopherson authored
Move the call to kvm_vfio_ops_exit() further up kvm_exit() to try and bring some amount of symmetry to the setup order in kvm_init(), and more importantly so that the arch hooks are invoked dead last by kvm_exit(). This will allow arch code to move away from the arch hooks without any change in ordering between arch code and common code in kvm_exit(). That kvm_vfio_ops_exit() is called last appears to be 100% arbitrary. It was bolted on after the fact by commit 571ee1b6 ("kvm: vfio: fix unregister kvm_device_ops of vfio"). The nullified kvm_device_ops_table is also local to kvm_main.c and is used only when there are active VMs, so unless arch code is doing something truly bizarre, nullifying the table earlier in kvm_exit() is little more than a nop. Signed-off-by:
Cornelia Huck <cohuck@redhat.com> Reviewed-by:
-
Sean Christopherson authored
Allocate cpus_hardware_enabled after arch hardware setup so that arch "init" and "hardware setup" are called back-to-back and thus can be combined in a future patch. cpus_hardware_enabled is never used before kvm_create_vm(), i.e. doesn't have a dependency with hardware setup and only needs to be allocated before /dev/kvm is exposed to userspace. Free the object before the arch hooks are invoked to maintain symmetry, and so that arch code can move away from the hooks without having to worry about ordering changes. Signed-off-by:
-
