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From: Sean Christopherson <seanjc@google.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Lai Jiangshan <laijs@linux.alibaba.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: X86: reset and read st->preempted in atomic way
Date: Tue, 8 Jun 2021 00:33:54 +0000	[thread overview]
Message-ID: <YL668lnelAVNlLWx@google.com> (raw)
In-Reply-To: <20210531174628.10265-1-jiangshanlai@gmail.com>

Nit: the shortlog is somewhat inaccurate now, maybe just:

  KVM: x86: Ensure PV TLB flush tracepoint reflects KVM behavior

or something along those lines.  Not sure what the best wording is :-/

On Tue, Jun 01, 2021, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
> 
> In record_steal_time(), st->preempted is read twice, and
> trace_kvm_pv_tlb_flush() might output result inconsistent if
> kvm_vcpu_flush_tlb_guest() see a different st->preempted later.
> 
> It is a very trivial problem and hardly has actual harm and can be
> avoided by reseting and reading st->preempted in atomic way via xchg().
> 
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>

I saw this quirk too, but couldn't quite bring myself to care enought to test a
patch :-)

Reviewed-by: Sean Christopherson <seanjc@google.com> 

      reply	other threads:[~2021-06-08  0:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-27 17:33 [PATCH] KVM: X86: always reset st->preempted in record_steal_time() Lai Jiangshan
2021-05-28  6:12 ` Wanpeng Li
2021-05-31 17:46   ` [PATCH] KVM: X86: reset and read st->preempted in atomic way Lai Jiangshan
2021-06-08  0:33     ` Sean Christopherson [this message]

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