Re: [PATCH v2 00/43] KVM: Halt-polling and x86 APICv overhaul
From: Paolo Bonzini
Date: Mon Oct 25 2021 - 10:14:09 EST
On 09/10/21 04:11, Sean Christopherson wrote:
This is basically two series smushed into one. The first "half" aims
to differentiate between "halt" and a more generic "block", where "halt"
aligns with x86's HLT instruction, the halt-polling mechanisms, and
associated stats, and "block" means any guest action that causes the vCPU
to block/wait.
The second "half" overhauls x86's APIC virtualization code (Posted
Interrupts on Intel VMX, AVIC on AMD SVM) to do their updates in response
to vCPU (un)blocking in the vcpu_load/put() paths, keying off of the
vCPU's rcuwait status to determine when a blocking vCPU is being put and
reloaded. This idea comes from arm64's kvm_timer_vcpu_put(), which I
stumbled across when diving into the history of arm64's (un)blocking hooks.
The x86 APICv overhaul allows for killing off several sets of hooks in
common KVM and in x86 KVM (to the vendor code). Moving everything to
vcpu_put/load() also realizes nice cleanups, especially for the Posted
Interrupt code, which required some impressive mental gymnastics to
understand how vCPU task migration interacted with vCPU blocking.
Non-x86 folks, sorry for the noise. I'm hoping the common parts can get
applied without much fuss so that future versions can be x86-only.
v2:
- Collect reviews. [Christian, David]
- Add patch to move arm64 WFI functionality out of hooks. [Marc]
- Add RISC-V to the fun.
- Add all the APICv fun.
v1: https://lkml.kernel.org/r/20210925005528.1145584-1-seanjc@xxxxxxxxxx
Jing Zhang (1):
KVM: stats: Add stat to detect if vcpu is currently blocking
Sean Christopherson (42):
KVM: VMX: Don't unblock vCPU w/ Posted IRQ if IRQs are disabled in
guest
KVM: SVM: Ensure target pCPU is read once when signalling AVIC
doorbell
KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPU
KVM: Force PPC to define its own rcuwait object
KVM: Update halt-polling stats if and only if halt-polling was
attempted
KVM: Refactor and document halt-polling stats update helper
KVM: Reconcile discrepancies in halt-polling stats
KVM: s390: Clear valid_wakeup in kvm_s390_handle_wait(), not in arch
hook
KVM: Drop obsolete kvm_arch_vcpu_block_finish()
KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook
KVM: Don't block+unblock when halt-polling is successful
KVM: x86: Tweak halt emulation helper names to free up kvm_vcpu_halt()
KVM: Rename kvm_vcpu_block() => kvm_vcpu_halt()
KVM: Split out a kvm_vcpu_block() helper from kvm_vcpu_halt()
KVM: Don't redo ktime_get() when calculating halt-polling
stop/deadline
KVM: x86: Directly block (instead of "halting") UNINITIALIZED vCPUs
KVM: x86: Invoke kvm_vcpu_block() directly for non-HALTED wait states
KVM: Add helpers to wake/query blocking vCPU
KVM: VMX: Skip Posted Interrupt updates if APICv is hard disabled
KVM: VMX: Clean up PI pre/post-block WARNs
KVM: VMX: Drop unnecessary PI logic to handle impossible conditions
KVM: VMX: Use boolean returns for Posted Interrupt "test" helpers
KVM: VMX: Drop pointless PI.NDST update when blocking
KVM: VMX: Save/restore IRQs (instead of CLI/STI) during PI pre/post
block
KVM: VMX: Read Posted Interrupt "control" exactly once per loop
iteration
KVM: VMX: Move Posted Interrupt ndst computation out of write loop
KVM: VMX: Remove vCPU from PI wakeup list before updating PID.NV
KVM: VMX: Handle PI wakeup shenanigans during vcpu_put/load
KVM: Drop unused kvm_vcpu.pre_pcpu field
KVM: Move x86 VMX's posted interrupt list_head to vcpu_vmx
KVM: VMX: Move preemption timer <=> hrtimer dance to common x86
KVM: x86: Unexport LAPIC's switch_to_{hv,sw}_timer() helpers
KVM: x86: Remove defunct pre_block/post_block kvm_x86_ops hooks
KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode
KVM: SVM: Don't bother checking for "running" AVIC when kicking for
IPIs
KVM: SVM: Unconditionally mark AVIC as running on vCPU load (with
APICv)
KVM: Drop defunct kvm_arch_vcpu_(un)blocking() hooks
KVM: VMX: Don't do full kick when triggering posted interrupt "fails"
KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this
vCPU
KVM: VMX: Pass desired vector instead of bool for triggering posted
IRQ
KVM: VMX: Fold fallback path into triggering posted IRQ helper
KVM: VMX: Don't do full kick when handling posted interrupt wakeup
arch/arm64/include/asm/kvm_emulate.h | 2 +
arch/arm64/include/asm/kvm_host.h | 1 -
arch/arm64/kvm/arch_timer.c | 5 +-
arch/arm64/kvm/arm.c | 60 +++---
arch/arm64/kvm/handle_exit.c | 5 +-
arch/arm64/kvm/psci.c | 2 +-
arch/mips/include/asm/kvm_host.h | 3 -
arch/mips/kvm/emulate.c | 2 +-
arch/powerpc/include/asm/kvm_host.h | 4 +-
arch/powerpc/kvm/book3s_pr.c | 2 +-
arch/powerpc/kvm/book3s_pr_papr.c | 2 +-
arch/powerpc/kvm/booke.c | 2 +-
arch/powerpc/kvm/powerpc.c | 5 +-
arch/riscv/include/asm/kvm_host.h | 1 -
arch/riscv/kvm/vcpu_exit.c | 2 +-
arch/s390/include/asm/kvm_host.h | 4 -
arch/s390/kvm/interrupt.c | 3 +-
arch/s390/kvm/kvm-s390.c | 7 +-
arch/x86/include/asm/kvm-x86-ops.h | 4 -
arch/x86/include/asm/kvm_host.h | 29 +--
arch/x86/kvm/lapic.c | 4 +-
arch/x86/kvm/svm/avic.c | 95 ++++-----
arch/x86/kvm/svm/svm.c | 8 -
arch/x86/kvm/svm/svm.h | 14 --
arch/x86/kvm/vmx/nested.c | 2 +-
arch/x86/kvm/vmx/posted_intr.c | 279 ++++++++++++---------------
arch/x86/kvm/vmx/posted_intr.h | 14 +-
arch/x86/kvm/vmx/vmx.c | 63 +++---
arch/x86/kvm/vmx/vmx.h | 3 +
arch/x86/kvm/x86.c | 55 ++++--
include/linux/kvm_host.h | 27 ++-
include/linux/kvm_types.h | 1 +
virt/kvm/async_pf.c | 2 +-
virt/kvm/kvm_main.c | 138 +++++++------
34 files changed, 413 insertions(+), 437 deletions(-)
Queued 1-20 and 22-28. Initially I skipped 21 because I didn't receive
it, but I have to think more about whether I agree with it.
In reality the CMPXCHG loops can really fail just once, because they
only race with the processor setting ON=1. But if the warnings were to
trigger at all, it would mean that something iffy is happening in the
pi_desc->control state machine, and having the check on every iteration
is (very marginally) more effective.
It's all theoretical, granted.
Paolo