linux-kernel - Re: [PATCH v2 06/11] KVM: x86: Don't bleed PVCLOCK_GUEST

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Message-ID: <e82ad865-8c04-404a-94e4-d9d7e5c10717@xen.org>
Date: Tue, 4 Feb 2025 09:28:42 +0000
From: Paul Durrant <xadimgnik@...il.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, David Woodhouse <dwmw2@...radead.org>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+352e553a86e0d75f5120@...kaller.appspotmail.com,
 Paul Durrant <pdurrant@...zon.com>, David Woodhouse <dwmw@...zon.co.uk>,
 Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH v2 06/11] KVM: x86: Don't bleed PVCLOCK_GUEST_STOPPED
 across PV clocks

On 01/02/2025 01:38, Sean Christopherson wrote:
> When updating a specific PV clock, make a full copy of KVM's reference
> copy/cache so that PVCLOCK_GUEST_STOPPED doesn't bleed across clocks.
> E.g. in the unlikely scenario the guest has enabled both kvmclock and Xen
> PV clock, a dangling GUEST_STOPPED in kvmclock would bleed into Xen PV
> clock.
> 
> Using a local copy of the pvclock structure also sets the stage for
> eliminating the per-vCPU copy/cache (only the TSC frequency information
> actually "needs" to be cached/persisted).
> 
> Fixes: aa096aa0a05f ("KVM: x86/xen: setup pvclock updates")
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/x86/kvm/x86.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@....org>