- 08 Dec, 2021 40 commits
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Lai Jiangshan authored
The value of host MSR_IA32_SYSENTER_ESP is known to be constant for each CPU: (cpu_entry_stack(cpu) + 1) when 32 bit syscall is enabled or NULL is 32 bit syscall is not enabled. So rdmsrl() can be avoided for the first case and both rdmsrl() and vmcs_writel() can be avoided for the second case. Signed-off-by:
Lai Jiangshan <laijs@linux.alibaba.com> Message-Id: <20211118110814.2568-3-jiangshanlai@gmail.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Lai Jiangshan authored
It is unchanged in most cases. Signed-off-by:
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Lai Jiangshan authored
It has no user. Signed-off-by:
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Paolo Bonzini authored
Document the meaning of the three combinations of regs_avail and regs_dirty. Update regs_dirty just after writeback instead of doing it later after vmexit. After vmexit, instead, we clear the regs_avail bits corresponding to lazily-loaded registers. Signed-off-by: -
Lai Jiangshan authored
When vcpu->arch.cr3 is changed, it is marked dirty, so vmcs.GUEST_CR3 can be updated only when kvm_register_is_dirty(vcpu, VCPU_EXREG_CR3). Signed-off-by:
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Lai Jiangshan authored
When vcpu->arch.cr3 is changed, it should be marked dirty unless it is being updated to the value of the architecture guest CR3 (i.e. VMX.GUEST_CR3 or vmcb->save.cr3 when tdp is enabled). This patch has no functionality changed because kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3) is superset of kvm_register_mark_available(vcpu, VCPU_EXREG_CR3) with additional change to vcpu->arch.regs_dirty, but no code uses regs_dirty for VCPU_EXREG_CR3. (vmx_load_mmu_pgd() uses vcpu->arch.regs_avail instead to test if VCPU_EXREG_CR3 dirty which means current code (ab)uses regs_avail for VCPU_EXREG_CR3 dirty information.) Signed-off-by:
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Lai Jiangshan authored
VCPU_EXREG_CR3 is never cleared from vcpu->arch.regs_avail or vcpu->arch.regs_dirty in SVM; therefore, marking CR3 as available is merely a NOP, and testing it will likewise always succeed. Signed-off-by:
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Lai Jiangshan authored
The comment had been added in the commit 689f3bf2 ("KVM: x86: unify callbacks to load paging root") and its related code was removed later, and it has nothing to do with the next line of code. So the comment should be removed too. Signed-off-by:
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Lai Jiangshan authored
Not functionality changed. Signed-off-by:
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Lai Jiangshan authored
In set_cr4_guest_host_mask(), all cr4 pdptr bits are already set to be intercepted in an unclear way. Add X86_CR4_PDPTR_BITS to make it clear and self-documented. No functionality changed. Signed-off-by:
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Lai Jiangshan authored
In set_cr4_guest_host_mask(), X86_CR4_PGE is set to be intercepted when !enable_ept just because X86_CR4_PGE is the only bit that is responsible for flushing TLB but listed in KVM_POSSIBLE_CR4_GUEST_BITS. It is clearer and self-documented to use X86_CR4_TLBFLUSH_BITS instead. No functionality changed. Signed-off-by:
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Lai Jiangshan authored
Use the same logic to handle the availability of VCPU_EXREG_PDPTR as VMX, also removing a branch in svm_vcpu_run(). Signed-off-by:
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Lai Jiangshan authored
mmu->pdptrs[] and vmcs.GUEST_PDPTR[0-3] are synced, so mmu->pdptrs is available and GUEST_PDPTR[0-3] is not dirty. Signed-off-by:
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Lai Jiangshan authored
For VMX with EPT, dirty PDPTRs need to be loaded before the next vmentry via vmx_load_mmu_pgd() But not all paths that call load_pdptrs() will cause vmx_load_mmu_pgd() to be invoked. Normally, kvm_mmu_reset_context() is used to cause KVM_REQ_LOAD_MMU_PGD, but sometimes it is skipped: * commit d81135a5("KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed") skips kvm_mmu_reset_context() after load_pdptrs() when changing CR0.CD and CR0.NW. * commit 21823fbd("KVM: x86: Invalidate all PGDs for the current PCID on MOV CR3 w/ flush") skips KVM_REQ_LOAD_MMU_PGD after load_pdptrs() when rewriting the CR3 with the same value. * commit a91a7c70("KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE") skips kvm_mmu_reset_context() after load_pdptrs() when changing CR4.PGE. Fixes: d81135a5 ("KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed") Fixes: 21823fbd ("KVM: x86: Invalidate all PGDs for the current PCID on MOV CR3 w/ flush") Fixes: a91a7c70 ("KVM: X86: Don't reset mmu context when toggling X86_CR4_PGE") Signed-off-by:
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Like Xu authored
For Intel, the guest PMU can be disabled via clearing the PMU CPUID. For AMD, all hw implementations support the base set of four performance counters, with current mainstream hardware indicating the presence of two additional counters via X86_FEATURE_PERFCTR_CORE. In the virtualized world, the AMD guest driver may detect the presence of at least one counter MSR. Most hypervisor vendors would introduce a module param (like lbrv for svm) to disable PMU for all guests. Another control proposal per-VM is to pass PMU disable information via MSR_IA32_PERF_CAPABILITIES or one bit in CPUID Fn4000_00[FF:00]. Both of methods require some guest-side changes, so a module parameter may not be sufficiently granular, but practical enough. Signed-off-by:
Like Xu <likexu@tencent.com> Message-Id: <20211117080304.38989-1-likexu@tencent.com> Signed-off-by:
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Sean Christopherson authored
Remove the vCPU from the wakeup list before updating the notification vector in the posted interrupt post-block helper. There is no need to wake the current vCPU as it is by definition not blocking. Practically speaking this is a nop as it only shaves a few meager cycles in the unlikely case that the vCPU was migrated and the previous pCPU gets a wakeup IRQ right before PID.NV is updated. The real motivation is to allow for more readable code in the future, when post-block is merged with vmx_vcpu_pi_load(), at which point removal from the list will be conditional on the old notification vector. Opportunistically add comments to document why KVM has a per-CPU spinlock that, at first glance, appears to be taken only on the owning CPU. Explicitly call out that the spinlock must be taken with IRQs disabled, a detail that was "lost" when KVM switched from spin_lock_irqsave() to spin_lock(), with IRQs disabled for the entirety of the relevant path. Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20211009021236.4122790-29-seanjc@google.com> Signed-off-by:
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Sean Christopherson authored
Hoist the CPU => APIC ID conversion for the Posted Interrupt descriptor out of the loop to write the descriptor, preemption is disabled so the CPU won't change, and if the APIC ID changes KVM has bigger problems. No functional change intended. Signed-off-by:
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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:
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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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