From: Maxim Levitsky <mlevitsk@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Marc Zyngier <maz@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Paul Mackerras <paulus@ozlabs.org>,
Anup Patel <anup.patel@wdc.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Atish Patra <atish.patra@wdc.com>,
David Hildenbrand <david@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
kvm@vger.kernel.org, kvm-ppc@vger.kernel.org,
kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
linux-kernel@vger.kernel.org,
David Matlack <dmatlack@google.com>,
Oliver Upton <oupton@google.com>,
Jing Zhang <jingzhangos@google.com>
Subject: Re: [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful
Date: Wed, 27 Oct 2021 16:40:40 +0300 [thread overview]
Message-ID: <cceb33be9e2a6ac504bb95a7b2b8cf5fe0b1ff26.camel@redhat.com> (raw)
In-Reply-To: <20211009021236.4122790-12-seanjc@google.com>
On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> 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 as 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: Sean Christopherson <seanjc@google.com>
> ---
> virt/kvm/kvm_main.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f90b3ed05628..227f6bbe0716 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3235,8 +3235,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> bool waited = false;
> u64 block_ns;
>
> - kvm_arch_vcpu_blocking(vcpu);
> -
> start = cur = poll_end = ktime_get();
> if (do_halt_poll) {
> ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns);
> @@ -3253,6 +3251,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> } while (kvm_vcpu_can_poll(cur, stop));
> }
>
> + kvm_arch_vcpu_blocking(vcpu);
>
> prepare_to_rcuwait(wait);
> for (;;) {
> @@ -3265,6 +3264,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> schedule();
> }
> finish_rcuwait(wait);
> +
> + kvm_arch_vcpu_unblocking(vcpu);
> +
> cur = ktime_get();
> if (waited) {
> vcpu->stat.generic.halt_wait_ns +=
> @@ -3273,7 +3275,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> ktime_to_ns(cur) - ktime_to_ns(poll_end));
> }
> out:
> - kvm_arch_vcpu_unblocking(vcpu);
> block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
>
> /*
Makes sense.
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
Maxim Levitsky
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-10-27 13:42 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 2:11 [PATCH v2 00/43] KVM: Halt-polling and x86 APICv overhaul Sean Christopherson
2021-10-09 2:11 ` [PATCH v2 01/43] KVM: VMX: Don't unblock vCPU w/ Posted IRQ if IRQs are disabled in guest Sean Christopherson
2021-10-09 2:11 ` [PATCH v2 02/43] KVM: SVM: Ensure target pCPU is read once when signalling AVIC doorbell Sean Christopherson
2021-10-25 13:21 ` Paolo Bonzini
2021-10-27 9:50 ` Maxim Levitsky
2021-10-09 2:11 ` [PATCH v2 03/43] KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPU Sean Christopherson
2021-10-09 2:11 ` [PATCH v2 04/43] KVM: Force PPC to define its own rcuwait object Sean Christopherson
2021-10-09 2:11 ` [PATCH v2 05/43] KVM: Update halt-polling stats if and only if halt-polling was attempted Sean Christopherson
2021-10-27 10:18 ` Maxim Levitsky
2021-10-09 2:11 ` [PATCH v2 06/43] KVM: Refactor and document halt-polling stats update helper Sean Christopherson
2021-10-27 10:56 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 07/43] KVM: Reconcile discrepancies in halt-polling stats Sean Christopherson
2021-10-27 11:29 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 08/43] KVM: s390: Clear valid_wakeup in kvm_s390_handle_wait(), not in arch hook Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 09/43] KVM: Drop obsolete kvm_arch_vcpu_block_finish() Sean Christopherson
2021-10-22 15:02 ` Anup Patel
2021-10-09 2:12 ` [PATCH v2 10/43] KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook Sean Christopherson
2021-10-25 13:31 ` Paolo Bonzini
2021-10-26 15:41 ` Marc Zyngier
2021-10-26 16:12 ` Paolo Bonzini
2021-11-30 11:39 ` Paolo Bonzini
2021-11-30 12:04 ` Marc Zyngier
2021-11-30 16:07 ` Paolo Bonzini
2021-10-09 2:12 ` [PATCH v2 11/43] KVM: Don't block+unblock when halt-polling is successful Sean Christopherson
2021-10-27 13:40 ` Maxim Levitsky [this message]
2021-11-28 22:16 ` Maxim Levitsky
2021-11-29 17:25 ` Sean Christopherson
2021-11-29 17:53 ` Paolo Bonzini
2021-11-29 18:55 ` Sean Christopherson
2021-11-29 19:18 ` Paolo Bonzini
2021-11-29 22:53 ` Maxim Levitsky
2021-12-02 0:20 ` Maxim Levitsky
2021-12-02 2:00 ` Sean Christopherson
2021-12-02 10:31 ` Paolo Bonzini
2021-11-29 17:55 ` Paolo Bonzini
2021-11-29 22:55 ` Maxim Levitsky
2021-12-02 10:20 ` Maxim Levitsky
2021-12-02 10:47 ` Maxim Levitsky
2021-12-02 12:02 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 12/43] KVM: x86: Tweak halt emulation helper names to free up kvm_vcpu_halt() Sean Christopherson
2021-10-27 14:10 ` Maxim Levitsky
2021-10-27 14:18 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 13/43] KVM: Rename kvm_vcpu_block() => kvm_vcpu_halt() Sean Christopherson
2021-10-22 15:04 ` Anup Patel
2021-10-09 2:12 ` [PATCH v2 14/43] KVM: Split out a kvm_vcpu_block() helper from kvm_vcpu_halt() Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 15/43] KVM: stats: Add stat to detect if vcpu is currently blocking Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 16/43] KVM: Don't redo ktime_get() when calculating halt-polling stop/deadline Sean Christopherson
2021-10-25 14:26 ` Paolo Bonzini
2021-10-27 14:35 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 17/43] KVM: x86: Directly block (instead of "halting") UNINITIALIZED vCPUs Sean Christopherson
2021-10-27 14:46 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 18/43] KVM: x86: Invoke kvm_vcpu_block() directly for non-HALTED wait states Sean Christopherson
2021-10-27 15:18 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 19/43] KVM: Add helpers to wake/query blocking vCPU Sean Christopherson
2021-10-25 14:06 ` Paolo Bonzini
2021-10-27 19:27 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 20/43] KVM: VMX: Skip Posted Interrupt updates if APICv is hard disabled Sean Christopherson
2021-10-25 13:48 ` Paolo Bonzini
2021-10-28 9:12 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 21/43] KVM: VMX: Clean up PI pre/post-block WARNs Sean Christopherson
2021-10-28 10:20 ` Maxim Levitsky
2021-10-28 15:34 ` Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 22/43] KVM: VMX: Drop unnecessary PI logic to handle impossible conditions Sean Christopherson
2021-10-25 13:53 ` Paolo Bonzini
2021-10-28 14:36 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 23/43] KVM: VMX: Use boolean returns for Posted Interrupt "test" helpers Sean Christopherson
2021-10-28 6:05 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 24/43] KVM: VMX: Drop pointless PI.NDST update when blocking Sean Christopherson
2021-10-25 14:01 ` Paolo Bonzini
2021-10-27 14:26 ` Sean Christopherson
2021-10-28 10:53 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 25/43] KVM: VMX: Save/restore IRQs (instead of CLI/STI) during PI pre/post block Sean Christopherson
2021-10-28 10:54 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 26/43] KVM: VMX: Read Posted Interrupt "control" exactly once per loop iteration Sean Christopherson
2021-10-28 10:58 ` Maxim Levitsky
2021-10-28 15:55 ` Sean Christopherson
2021-10-31 22:48 ` Maxim Levitsky
2021-11-01 17:41 ` Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 27/43] KVM: VMX: Move Posted Interrupt ndst computation out of write loop Sean Christopherson
2021-10-28 11:28 ` Maxim Levitsky
2021-10-28 16:09 ` Maxim Levitsky
2021-10-28 16:12 ` Sean Christopherson
2021-10-31 22:51 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 28/43] KVM: VMX: Remove vCPU from PI wakeup list before updating PID.NV Sean Christopherson
2021-10-28 12:53 ` Maxim Levitsky
2021-10-28 17:19 ` Sean Christopherson
2021-10-31 22:52 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 29/43] KVM: VMX: Handle PI wakeup shenanigans during vcpu_put/load Sean Christopherson
2021-10-28 15:14 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 30/43] KVM: Drop unused kvm_vcpu.pre_pcpu field Sean Christopherson
2021-10-28 15:16 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 31/43] KVM: Move x86 VMX's posted interrupt list_head to vcpu_vmx Sean Christopherson
2021-10-28 15:33 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 32/43] KVM: VMX: Move preemption timer <=> hrtimer dance to common x86 Sean Christopherson
2021-10-28 15:45 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 33/43] KVM: x86: Unexport LAPIC's switch_to_{hv, sw}_timer() helpers Sean Christopherson
2021-10-28 15:45 ` [PATCH v2 33/43] KVM: x86: Unexport LAPIC's switch_to_{hv,sw}_timer() helpers Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 34/43] KVM: x86: Remove defunct pre_block/post_block kvm_x86_ops hooks Sean Christopherson
2021-10-28 15:46 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 35/43] KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode Sean Christopherson
2021-10-25 14:26 ` Paolo Bonzini
2021-10-27 15:06 ` Sean Christopherson
2021-10-27 15:36 ` Paolo Bonzini
2021-10-27 16:08 ` Sean Christopherson
2021-10-27 16:14 ` Paolo Bonzini
2021-10-28 16:12 ` Maxim Levitsky
2021-10-28 17:06 ` Sean Christopherson
2021-10-09 2:12 ` [PATCH v2 36/43] KVM: SVM: Don't bother checking for "running" AVIC when kicking for IPIs Sean Christopherson
2021-10-31 14:50 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 37/43] KVM: SVM: Unconditionally mark AVIC as running on vCPU load (with APICv) Sean Christopherson
2021-10-25 14:22 ` Paolo Bonzini
2021-10-25 15:48 ` Sean Christopherson
2021-10-25 15:57 ` Paolo Bonzini
2021-10-25 16:00 ` Sean Christopherson
2021-10-31 16:34 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 38/43] KVM: Drop defunct kvm_arch_vcpu_(un)blocking() hooks Sean Christopherson
2021-10-31 16:35 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 39/43] KVM: VMX: Don't do full kick when triggering posted interrupt "fails" Sean Christopherson
2021-10-25 14:34 ` Paolo Bonzini
2021-10-27 16:04 ` Sean Christopherson
2021-10-27 22:09 ` Paolo Bonzini
2021-10-31 22:15 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 40/43] KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this vCPU Sean Christopherson
2021-10-25 15:05 ` Paolo Bonzini
2021-10-27 15:30 ` Sean Christopherson
2021-10-31 22:19 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 41/43] KVM: VMX: Pass desired vector instead of bool for triggering posted IRQ Sean Christopherson
2021-10-31 22:25 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 42/43] KVM: VMX: Fold fallback path into triggering posted IRQ helper Sean Christopherson
2021-10-31 22:30 ` Maxim Levitsky
2021-10-09 2:12 ` [PATCH v2 43/43] KVM: VMX: Don't do full kick when handling posted interrupt wakeup Sean Christopherson
2021-10-25 14:16 ` Paolo Bonzini
2021-10-31 22:33 ` Maxim Levitsky
2021-10-25 14:13 ` [PATCH v2 00/43] KVM: Halt-polling and x86 APICv overhaul Paolo Bonzini
2021-10-27 14:41 ` Sean Christopherson
2021-10-27 14:57 ` Paolo Bonzini
2021-10-27 15:28 ` Sean Christopherson
2021-10-27 15:37 ` Paolo Bonzini
2021-10-26 7:20 ` Christian Borntraeger
2021-10-26 14:48 ` Sean Christopherson
2021-10-26 18:29 ` Christian Borntraeger
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