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Message-ID: <055482bec09cae1ea56f979893c6b67e9d6b26a2.camel@infradead.org>
Subject: Re: [PATCH v4] KVM: x86/tsc: Don't sync user changes to TSC with
 KVM-initiated change
From:   David Woodhouse <dwmw2@infradead.org>
To:     Sean Christopherson <seanjc@google.com>,
        Like Xu <like.xu.linux@gmail.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Oliver Upton <oliver.upton@linux.dev>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Wed, 13 Sep 2023 10:31:24 +0200
In-Reply-To: <ZNa9QyRmuAjNAonC@google.com>
References: <20230801034524.64007-1-likexu@tencent.com>
         <ZNa9QyRmuAjNAonC@google.com>
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On Fri, 2023-08-11 at 15:59 -0700, Sean Christopherson wrote:
> On Tue, Aug 01, 2023, Like Xu wrote:
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 278dbd37dab2..eeaf4ad9174d 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2713,7 +2713,7 @@ static void __kvm_synchronize_tsc(struct kvm_vcpu=
 *vcpu, u64 offset, u64 tsc,
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0kvm_track_tsc_matching(=
vcpu);
> > =C2=A0 }
> > =C2=A0=20
> > -static void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 data)
> > +static void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 data, bool =
user_initiated)
>=20
> Rather than pass two somewhat magic values for the KVM-internal call, wha=
t about
> making @data a pointer and passing NULL?

Why change that at all?

Userspace used to be able to force a sync by writing zero. You are
removing that from the ABI without any explanation about why; it
doesn't seem necessary for fixing the original issue.

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