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From:   Paul Durrant <xadimgnik@gmail.com>
Message-ID: <f850458d-c1a3-4851-921e-e04404e827b9@xen.org>
Date:   Wed, 1 Nov 2023 11:02:16 +0000
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Reply-To: paul@xen.org
Subject: Re: [PATCH v2] KVM x86/xen: add an override for
 PVCLOCK_TSC_STABLE_BIT
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To:     David Woodhouse <dwmw2@infradead.org>,
        Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20231031115748.622578-1-paul@xen.org>
 <ZUGCPQegUeTutsrb@google.com>
 <028f629d16377f9a7e9fd87ef9564846b0ab4ed9.camel@infradead.org>
Organization: Xen Project
In-Reply-To: <028f629d16377f9a7e9fd87ef9564846b0ab4ed9.camel@infradead.org>
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On 31/10/2023 22:48, David Woodhouse wrote:
> On Tue, 2023-10-31 at 15:39 -0700, Sean Christopherson wrote:
>> On Tue, Oct 31, 2023, Paul Durrant wrote:
>>>
>>> +       if (force_tsc_unstable)
>>> +               guest_hv_clock->flags &= ~PVCLOCK_TSC_STABLE_BIT;
>>
>> I don't see how this works.  This clears the bit in the guest copy, then clobbers
>> all of guest_hv_clock with a memcpy().
> 
> Agreed, that seems wrong.
> 

It is indeed. Looks like it got moved the wrong side of the memcpy() 
when I rebased.

   Paul