From: Marc Zyngier <maz@kernel.org>
To: Dongli Zhang <dongli.zhang@oracle.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev,
linux-kselftest@vger.kernel.org, seanjc@google.com,
pbonzini@redhat.com, oupton@kernel.org, fuad.tabba@linux.dev,
joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com,
yuzenghui@huawei.com, dwmw2@infradead.org, joe.jin@oracle.com
Subject: Re: [PATCH 0/4] KVM: Reset steal time accounting on vCPU pid change (x86 and arm64)
Date: Mon, 17 Aug 2026 09:15:02 +0100 [thread overview]
Message-ID: <86tsotyxh5.wl-maz@kernel.org> (raw)
In-Reply-To: <20260816053630.527528-1-dongli.zhang@oracle.com>
On Sun, 16 Aug 2026 06:33:01 +0100,
Dongli Zhang <dongli.zhang@oracle.com> wrote:
[...]
> 4. Guest kernel changes are not included. I may send it separately to keep
> this series limited to the KVM hypervisor.
Hold on. Do you mean you are changing the guest visible behaviour of a
PV interface? That's an ABI. It *cannot* change unilaterally.
>
> [PATCH 1/5] x86/kvm: Reset prev_steal_time and prev_steal_time_rq when enabling steal time
> https://lore.kernel.org/all/20260505003044.78693-2-dongli.zhang@oracle.com
>
> 5. There is one remaining corner case: this series resets last_steal when
> the vCPU run PID changes, but not when steal time is enabled. If additional
> host run_delay is accumulated after the PID changes but before the guest
> enables steal time, that delta could be unexpectedly accounted to guest
> vCPU steal time. In practice, this should not happen for Linux guests.
Why is Linux immune to this? Also, KVM does not cater for Linux guests
only.
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2026-08-17 8:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-16 5:33 [PATCH 0/4] KVM: Reset steal time accounting on vCPU pid change (x86 and arm64) Dongli Zhang
2026-08-16 5:33 ` [PATCH 1/4] KVM: x86: Reset last_steal on vCPU pid change Dongli Zhang
2026-08-16 5:55 ` sashiko-bot
2026-08-16 5:33 ` [PATCH 2/4] KVM: arm64: " Dongli Zhang
2026-08-17 8:42 ` Marc Zyngier
2026-08-16 5:33 ` [PATCH 3/4] KVM: selftests: Test steal time across vCPU pid changes on x86 Dongli Zhang
2026-08-16 5:55 ` sashiko-bot
2026-08-16 5:33 ` [PATCH 4/4] KVM: selftests: Add arm64 coverage for steal time pid changes Dongli Zhang
2026-08-17 8:15 ` Marc Zyngier [this message]
2026-08-17 11:51 ` [PATCH 0/4] KVM: Reset steal time accounting on vCPU pid change (x86 and arm64) David Woodhouse
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