- 08 Dec, 2021 40 commits
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Sean Christopherson authored
Use READ_ONCE() when loading the posted interrupt descriptor control field to ensure "old" and "new" have the same base value. If the compiler emits separate loads, and loads into "new" before "old", KVM could theoretically drop the ON bit if it were set between the loads. Fixes: 28b835d6 ("KVM: Update Posted-Interrupts Descriptor when vCPU is preempted") Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20211009021236.4122790-27-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Sean Christopherson authored
Save/restore IRQs when disabling IRQs in posted interrupt pre/post block in preparation for moving the code into vcpu_put/load(), where it would be called with IRQs already disabled. No functional changed intended. Signed-off-by:
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Sean Christopherson authored
Don't update Posted Interrupt's NDST, a.k.a. the target pCPU, in the pre-block path, as NDST is guaranteed to be up-to-date. The comment about the vCPU being preempted during the update is simply wrong, as the update path runs with IRQs disabled (from before snapshotting vcpu->cpu, until after the update completes). Since commit 8b306e2f ("KVM: VMX: avoid double list add with VT-d posted interrupts", 2017-09-27) The vCPU can get preempted _before_ the update starts, but not during. And if the vCPU is preempted before, vmx_vcpu_pi_load() is responsible for updating NDST when the vCPU is scheduled back in. In that case, the check against the wakeup vector in vmx_vcpu_pi_load() cannot be true as that would require the notification vector to have been set to the wakeup vector _before_ blocking. Opportunistically switch to using vcpu->cpu for the list/lock lookups, which do not need pre_pcpu since the same commit. Signed-off-by:
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Sean Christopherson authored
Return bools instead of ints for the posted interrupt "test" helpers. The bit position of the flag being test does not matter to the callers, and is in fact lost by virtue of test_bit() itself returning a bool. Returning ints is potentially dangerous, e.g. "pi_test_on(pi_desc) == 1" is safe-ish because ON is bit 0 and thus any sane implementation of pi_test_on() will work, but for SN (bit 1), checking "== 1" would rely on pi_test_on() to return 0 or 1, a.k.a. bools, as opposed to 0 or 2 (the positive bit position). Signed-off-by:
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Sean Christopherson authored
Drop sanity checks on the validity of the previous pCPU when handling vCPU block/unlock for posted interrupts. The intention behind the sanity checks is to avoid memory corruption in case of a race or incorrect locking, but the code has been stable for a few years now and the checks get in the way of eliminating kvm_vcpu.pre_cpu. Signed-off-by:
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Sean Christopherson authored
Explicitly skip posted interrupt updates if APICv is disabled in all of KVM, or if the guest doesn't have an in-kernel APIC. The PI descriptor is kept up-to-date if APICv is inhibited, e.g. so that re-enabling APICv doesn't require a bunch of updates, but neither the module param nor the APIC type can be changed on-the-fly. Signed-off-by:
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Sean Christopherson authored
Add helpers to wake and query a blocking vCPU. In addition to providing nice names, the helpers reduce the probability of KVM neglecting to use kvm_arch_vcpu_get_wait(). No functional change intended. Signed-off-by:
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Sean Christopherson authored
Call kvm_vcpu_block() directly for all wait states except HALTED so that kvm_vcpu_halt() is no longer a misnomer on x86. Functionally, this means KVM will never attempt halt-polling or adjust vcpu->halt_poll_ns for INIT_RECEIVED (a.k.a. Wait-For-SIPI (WFS)) or AP_RESET_HOLD; UNINITIALIZED is handled in kvm_arch_vcpu_ioctl_run(), and x86 doesn't use any other "wait" states. As mentioned above, the motivation of this is purely so that "halt" isn't overloaded on x86, e.g. in KVM's stats. Skipping halt-polling for WFS (and RESET_HOLD) has no meaningful effect on guest performance as there are typically single-digit numbers of INIT-SIPI sequences per AP vCPU, per boot, versus thousands of HLTs just to boot to console. Reviewed-by:
David Matlack <dmatlack@google.com> Signed-off-by:
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Sean Christopherson authored
Go directly to kvm_vcpu_block() when handling the case where userspace attempts to run an UNINITIALIZED vCPU. The vCPU is not halted, nor is it likely that halt-polling will be successful in this case. Reviewed-by:
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Sean Christopherson authored
Calculate the halt-polling "stop" time using "start" instead of redoing ktime_get(). In practice, the numbers involved are in the noise (e.g., in the happy case where hardware correctly predicts do_halt_poll and there are no interrupts, "start" is probably only a few cycles old) and either approach is perfectly ok. But it's more precise to count any extra latency toward the halt-polling time. Reviewed-by:
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Jing Zhang authored
Add a "blocking" stat that userspace can use to detect the case where a vCPU is not being run because of an vCPU/guest action, e.g. HLT or WFS on x86, WFI on arm64, etc... Current guest/host/halt stats don't show this well, e.g. if a guest halts for a long period of time then the vCPU could could appear pathologically blocked due to a host condition, when in reality the vCPU has been put into a not-runnable state by the guest. Originally-by:
Cannon Matthews <cannonmatthews@google.com> Suggested-by:
Jing Zhang <jingzhangos@google.com> [sean: renamed stat to "blocking", massaged changelog] Signed-off-by:
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Sean Christopherson authored
Factor out the "block" part of kvm_vcpu_halt() so that x86 can emulate non-halt wait/sleep/block conditions that should not be subjected to halt-polling. No functional change intended. Reviewed-by:
Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by:
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Sean Christopherson authored
Rename kvm_vcpu_block() to kvm_vcpu_halt() in preparation for splitting the actual "block" sequences into a separate helper (to be named kvm_vcpu_block()). x86 will use the standalone block-only path to handle non-halt cases where the vCPU is not runnable. Rename block_ns to halt_ns to match the new function name. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Drop kvm_arch_vcpu_block_finish() now that all arch implementations are nops. No functional change intended. Acked-by:
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Sean Christopherson authored
Rename a variety of HLT-related helpers to free up the function name "kvm_vcpu_halt" for future use in generic KVM code, e.g. to differentiate between "block" and "halt". No functional change intended. Reviewed-by:
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Sean Christopherson authored
Invoke the arch hooks for block+unblock if and only if KVM actually attempts to block the vCPU. The only non-nop implementation is on x86, specifically SVM's AVIC, and there is no need to put the AVIC prior to halt-polling; KVM x86's kvm_vcpu_has_events() will scour the full vIRR to find pending IRQs regardless of whether the AVIC is loaded/"running". The primary motivation is to allow future cleanup to split out "block" from "halt", but this is also likely a small performance boost on x86 SVM when halt-polling is successful. Adjust the post-block path to update "cur" after unblocking, i.e. include AVIC load time in halt_wait_ns and halt_wait_hist, so that the behavior is consistent. Moving just the pre-block arch hook would result in only the AVIC put latency being included in the halt_wait stats. There is no obvious evidence that one way or the other is correct, so just ensure KVM is consistent. Note, x86 has two separate paths for handling APICv with respect to vCPU blocking. VMX uses hooks in x86's vcpu_block(), while SVM uses the arch hooks in kvm_vcpu_block(). Prior to this path, the two paths were more or less functionally identical. That is very much not the case after this patch, as the hooks used by VMX _must_ fire before halt-polling. x86's entire mess will be cleaned up in future patches. Signed-off-by:
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Sean Christopherson authored
Move the put and reload of the vGIC out of the block/unblock callbacks and into a dedicated WFI helper. Functionally, this is nearly a nop as the block hook is called at the very beginning of kvm_vcpu_block(), and the only code in kvm_vcpu_block() after the unblock hook is to update the halt-polling controls, i.e. can only affect the next WFI. Back when the arch (un)blocking hooks were added by commits 3217f7c2 ("KVM: Add kvm_arch_vcpu_{un}blocking callbacks) and d35268da ("arm/arm64: KVM: arch_timer: Only schedule soft timer on vcpu_block"), the hooks were invoked only when KVM was about to "block", i.e. schedule out the vCPU. The use case at the time was to schedule a timer in the host based on the earliest timer in the guest in order to wake the blocking vCPU when the emulated guest timer fired. Commit accb99bc ("KVM: arm/arm64: Simplify bg_timer programming") reworked the timer logic to be even more precise, by waiting until the vCPU was actually scheduled out, and so move the timer logic from the (un)blocking hooks to vcpu_load/put. In the meantime, the hooks gained usage for enabling vGIC v4 doorbells in commit df9ba959 ("KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking source"), and added related logic for the VMCR in commit 5eeaf10e ("KVM: arm/arm64: Sync ICH_VMCR_EL2 back when about to block"). Finally, commit 07ab0f8d ("KVM: Call kvm_arch_vcpu_blocking early into the blocking sequence") hoisted the (un)blocking hooks so that they wrapped KVM's halt-polling logic in addition to the core "block" logic. In other words, the original need for arch hooks to take action _only_ in the block path is long since gone. Cc: Oliver Upton <oupton@google.com> Cc: Marc Zyngier <maz@kernel.org> Signed-off-by:
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Sean Christopherson authored
Move the clearing of valid_wakeup from kvm_arch_vcpu_block_finish() so that a future patch can drop said arch hook. Unlike the other blocking- related arch hooks, vcpu_blocking/unblocking(), vcpu_block_finish() needs to be called even if the KVM doesn't actually block the vCPU. This will allow future patches to differentiate between truly blocking the vCPU and emulating a halt condition without introducing a contradiction. Alternatively, the hook could be renamed to kvm_arch_vcpu_halt_finish(), but there's literally one call site in s390, and future cleanup can also be done to handle valid_wakeup fully within kvm_s390_handle_wait() and allow generic KVM to drop vcpu_valid_wakeup(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the halt-polling "success" and histogram stats update into the dedicated helper to fix a discrepancy where the success/fail "time" stats consider polling successful so long as the wait is avoided, but the main "success" and histogram stats consider polling successful if and only if a wake event was detected by the halt-polling loop. Move halt_attempted_poll to the helper as well so that all the stats are updated in a single location. While it's a bit odd to update the stat well after the fact, practically speaking there's no meaningful advantage to updating before polling. Note, there is a functional change in addition to the success vs. fail change. The histogram updates previously called ktime_get() instead of using "cur". But that change is desirable as it means all the stats are now updated with the same polling time, and avoids the extra ktime_get(), which isn't expensive but isn't free either. Reviewed-by:
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Sean Christopherson authored
Add a comment to document that halt-polling is considered successful even if the polling loop itself didn't detect a wake event, i.e. if a wake event was detect in the final kvm_vcpu_check_block(). Invert the param to update helper so that the helper is a dumb function that is "told" whether or not polling was successful, as opposed to determining success based on blocking behavior. Opportunistically tweak the params to the update helper to reduce the line length for the call site so that it fits on a single line, and so that the prototype conforms to the more traditional kernel style. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Don't update halt-polling stats if halt-polling wasn't attempted. This is a nop as @poll_ns is guaranteed to be '0' (poll_end == start); in a future patch (to move the histogram stats into the helper), it will avoid to avoid a discrepancy in what is considered a "successful" halt-poll. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Do not define/reference kvm_vcpu.wait if __KVM_HAVE_ARCH_WQP is true, and instead force the architecture (PPC) to define its own rcuwait object. Allowing common KVM to directly access vcpu->wait without a guard makes it all too easy to introduce potential bugs, e.g. kvm_vcpu_block(), kvm_vcpu_on_spin(), and async_pf_execute() all operate on vcpu->wait, not the result of kvm_arch_vcpu_get_wait(), and so may do the wrong thing for PPC. Due to PPC's shenanigans with respect to callbacks and waits (it switches to the virtual core's wait object at KVM_RUN!?!?), it's not clear whether or not this fixes any bugs. Signed-off-by:
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Sean Christopherson authored
Wrap s390's halt_poll_max_steal with READ_ONCE and snapshot the result of kvm_arch_no_poll() in kvm_vcpu_block() to avoid a mostly-theoretical, largely benign bug on s390 where the result of kvm_arch_no_poll() could change due to userspace modifying halt_poll_max_steal while the vCPU is blocking. The bug is largely benign as it will either cause KVM to skip updating halt-polling times (no_poll toggles false=>true) or to update halt-polling times with a slightly flawed block_ns. Note, READ_ONCE is unnecessary in the current code, add it in case the arch hook is ever inlined, and to provide a hint that userspace can change the param at will. Fixes: 8b905d28 ("KVM: s390: provide kvm_arch_no_poll function") Reviewed-by:
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Sean Christopherson authored
Ensure vcpu->cpu is read once when signalling the AVIC doorbell. If the compiler rereads the field and the vCPU is migrated between the check and writing the doorbell, KVM would signal the wrong physical CPU. Functionally, signalling the wrong CPU in this case is not an issue as task migration means the vCPU has exited and will pick up any pending interrupts on the next VMRUN. Add the READ_ONCE() purely to clean up the code. Opportunistically add a comment explaining the task migration behavior, and rename cpuid=>cpu to avoid conflating the CPU number with KVM's more common usage of CPUID. Signed-off-by:
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Paolo Bonzini authored
Don't configure the wakeup handler when a vCPU is blocking with IRQs disabled, in which case any IRQ, posted or otherwise, should not be recognized and thus should not wake the vCPU. Fixes: bf9f6ac8 ("KVM: Update Posted-Interrupts Descriptor when vCPU is blocked") Signed-off-by:
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Vihas Mak authored
change 0 to false and 1 to true to fix following cocci warnings: arch/x86/kvm/mmu/mmu.c:1485:9-10: WARNING: return of 0/1 in function 'kvm_set_pte_rmapp' with return type bool arch/x86/kvm/mmu/mmu.c:1636:10-11: WARNING: return of 0/1 in function 'kvm_test_age_rmapp' with return type bool Signed-off-by:Vihas Mak <makvihas@gmail.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Message-Id: <20211114164312.GA28736@makvihas> Signed-off-by:
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Paolo Bonzini authored
If we do have the vcpu mutex, as is the case if kvm_running_vcpu is set to the target vcpu of the kick, changes to vcpu->mode do not need atomic operations; cmpxchg is only needed _outside_ the mutex to ensure that the IN_GUEST_MODE->EXITING_GUEST_MODE change does not race with the vcpu thread going OUTSIDE_GUEST_MODE. Use this to optimize the case of a vCPU sending an interrupt to itself. Signed-off-by: -
Ben Gardon authored
Remove the gotos from vmx_get_mt_mask. It's easier to build the whole memory type at once, than it is to combine separate cacheability and ipat fields. No functional change intended. Signed-off-by:
Ben Gardon <bgardon@google.com> Message-Id: <20211115234603.2908381-12-bgardon@google.com> Signed-off-by:
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Ben Gardon authored
In preparation for implementing in-place hugepage promotion, various functions will need to be called from zap_collapsible_spte_range, which has the const qualifier on its memslot argument. Propagate the const qualifier to the various functions which will be needed. This just serves to simplify the following patch. No functional change intended. Signed-off-by:
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Ben Gardon authored
The vCPU argument to mmu_try_to_unsync_pages is now only used to get a pointer to the associated struct kvm, so pass in the kvm pointer from the beginning to remove the need for a vCPU when calling the function. Signed-off-by:
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Ben Gardon authored
kvm_slot_page_track_is_active only uses its vCPU argument to get a pointer to the assoicated struct kvm, so just pass in the struct KVM to remove the need for a vCPU pointer. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Rework make_spte() to query the shadow page's role, specifically whether or not it's a guest_mode page, a.k.a. a page for L2, when determining if the SPTE is compatible with PML. This eliminates a dependency on @vcpu, with a future goal of being able to create SPTEs without a specific vCPU. Signed-off-by:
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Emanuele Giuseppe Esposito authored
This structure will replace vmcb_control_area in svm_nested_state, providing only the fields that are actually used by the nested state. This avoids having and copying around uninitialized fields. The cost of this, however, is that all functions (in this case vmcb_is_intercept) expect the old structure, so they need to be duplicated. In addition, in svm_get_nested_state() user space expects a vmcb_control_area struct, so we need to copy back all fields in a temporary structure before copying it to userspace. Signed-off-by:
Emanuele Giuseppe Esposito <eesposit@redhat.com> Reviewed-by:
Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20211103140527.752797-7-eesposit@redhat.com> Signed-off-by:
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Paolo Bonzini authored
Remove the struct vmcb_control_area parameter from nested_vmcb_check_controls, for consistency with the functions that operate on the save area. This way, VMRUN uses the version without underscores for both areas, while KVM_SET_NESTED_STATE uses the version with underscores. Signed-off-by: -
Emanuele Giuseppe Esposito authored
Use the already checked svm->nested.save cached fields (EFER, CR0, CR4, ...) instead of vmcb12's in nested_vmcb02_prepare_save(). This prevents from creating TOC/TOU races, since the guest could modify the vmcb12 fields. This also avoids the need of force-setting EFER_SVME in nested_vmcb02_prepare_save. Signed-off-by:
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Emanuele Giuseppe Esposito authored
Now that struct vmcb_save_area_cached contains the required vmcb fields values (done in nested_load_save_from_vmcb12()), check them to see if they are correct in nested_vmcb_valid_sregs(). While at it, rename nested_vmcb_valid_sregs in nested_vmcb_check_save. __nested_vmcb_check_save takes the additional @save parameter, so it is helpful when we want to check a non-svm save state, like in svm_set_nested_state. The reason for that is that save is the L1 state, not L2, so we check it without moving it to svm->nested.save. Signed-off-by:
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Emanuele Giuseppe Esposito authored
Following the same naming convention of the previous patch, rename nested_load_control_from_vmcb12. In addition, inline copy_vmcb_control_area as it is only called by this function. __nested_copy_vmcb_control_to_cache() works with vmcb_control_area parameters and it will be useful in next patches, when we use local variables instead of svm cached state. Signed-off-by:
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Emanuele Giuseppe Esposito authored
This is useful in the next patch, to keep a saved copy of vmcb12 registers and pass it around more easily. Instead of blindly copying everything, we just copy EFER, CR0, CR3, CR4, DR6 and DR7 which are needed by the VMRUN checks. If more fields will need to be checked, it will be quite obvious to see that they must be added in struct vmcb_save_area_cached and in nested_copy_vmcb_save_to_cache(). __nested_copy_vmcb_save_to_cache() takes a vmcb_save_area_cached parameter, which is useful in order to save the state to a local variable. Signed-off-by:
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Emanuele Giuseppe Esposito authored
Inline nested_vmcb_check_cr3_cr4 as it is not called by anyone else. Doing so simplifies next patches. Signed-off-by:
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Sean Christopherson authored
Allocate the "new" memslot for !DELETE memslot updates straight away instead of filling an intermediate on-stack object and forcing kvm_set_memslot() to juggle the allocation and do weird things like reuse the old memslot object in MOVE. In the MOVE case, this results in an "extra" memslot allocation due to allocating both the "new" slot and the "invalid" slot, but that's a temporary and not-huge allocation, and MOVE is a relatively rare memslot operation. Regarding MOVE, drop the open-coded management of the gfn tree with a call to kvm_replace_memslot(), which already handles the case where new->base_gfn != old->base_gfn. This is made possible by virtue of not having to copy the "new" memslot data after erasing the old memslot from the gfn tree. Using kvm_replace_memslot(), and more specifically not reusing the old memslot, means the MOVE case now does hva tree and hash list updates, but that's a small price to pay for simplifying the code and making MOVE align with all the other flavors of updates. The "extra" updates are firmly in the noise from a performance perspective, e.g. the "move (in)active area" selfttests show a (very, very) slight improvement. Signed-off-by:
Maciej S. Szmigiero <maciej.szmigiero@oracle.com> Signed-off-by:
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