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Message-ID: <YVOTYk9aSl72hCmX@google.com>
Date: Tue, 28 Sep 2021 22:12:50 +0000
From: David Matlack <dmatlack@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
Paul Mackerras <paulus@...abs.org>,
Christian Borntraeger <borntraeger@...ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....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, linux-kernel@...r.kernel.org,
Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH 13/14] KVM: x86: Directly block (instead of "halting")
UNINITIALIZED vCPUs
On Fri, Sep 24, 2021 at 05:55:27PM -0700, Sean Christopherson wrote:
> Go directly to kvm_vcpu_block() when handling the case where userspace
> attempts to run an UNINITIALIZED vCPU. The vCPU isn't halted and its time
> spent in limbo arguably should not be factored into halt-polling as the
> behavior of the VM at this point is not at all indicative of the behavior
> of the VM once it is up and running, i.e. executing HLT in idle tasks.
>
> Note, because this case is encountered only on the first run of an AP vCPU,
> vcpu->halt_poll_ns is guaranteed to be '0', and so KVM will not attempt
> halt-polling, i.e. this really only affects the post-block bookkeeping.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Reviewed-by: David Matlack <dmatlack@...gle.com>
> ---
> arch/x86/kvm/x86.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0d71c73a61bb..b444f9315766 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10127,7 +10127,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> r = -EINTR;
> goto out;
> }
> - kvm_vcpu_halt(vcpu);
> + kvm_vcpu_block(vcpu);
> if (kvm_apic_accept_events(vcpu) < 0) {
> r = 0;
> goto out;
> --
> 2.33.0.685.g46640cef36-goog
>
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