linux-kernel - Re: [PATCH v2] KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on

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Message-ID: <171754269008.2777502.9202264224544350112.b4-ty@google.com>
Date: Tue,  4 Jun 2024 16:29:19 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Rik van Riel <riel@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>, Avi Kivity <avi@...hat.com>, 
	Breno Leitao <leitao@...ian.org>
Cc: rbc@...a.com, paulmck@...nel.org, stable@...r.kernel.org, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()

On Fri, 10 May 2024 02:23:52 -0700, Breno Leitao wrote:
> Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the
> loads and stores are atomic.  In the extremely unlikely scenario the
> compiler tears the stores, it's theoretically possible for KVM to attempt
> to get a vCPU using an out-of-bounds index, e.g. if the write is split
> into multiple 8-bit stores, and is paired with a 32-bit load on a VM with
> 257 vCPUs:
> 
> [...]

Applied to kvm-x86 fixes, thanks!

[1/1] KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()
      https://github.com/kvm-x86/linux/commit/2b0844082557

--
https://github.com/kvm-x86/linux/tree/next