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Message-ID: <04b1a72e-47b4-4bde-eb9e-ba36c156ff0d@de.ibm.com>
Date: Tue, 26 Oct 2021 09:20:45 +0200
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Sean Christopherson <seanjc@...gle.com>,
Marc Zyngier <maz@...nel.org>,
Huacai Chen <chenhuacai@...nel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
Paul Mackerras <paulus@...abs.org>,
Anup Patel <anup.patel@....com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Janosch Frank <frankja@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Atish Patra <atish.patra@....com>,
David Hildenbrand <david@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-mips@...r.kernel.org, kvm@...r.kernel.org,
kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
David Matlack <dmatlack@...gle.com>,
Oliver Upton <oupton@...gle.com>,
Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 00/43] KVM: Halt-polling and x86 APICv overhaul
Am 09.10.21 um 04:11 schrieb Sean Christopherson:
> 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.
Have we actually followed up on the regression regarding halt_poll_ns=0 no longer disabling
polling for running systems?
>
> v1: https://lkml.kernel.org/r/20210925005528.1145584-1-seanjc@google.com
>
> 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(-)
>
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