linux-kernel - Re: [PATCH 7/9] KVM: x86: simplify dr6 accessors in kvm_x86

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Message-ID: <20200506160623.GO6299@xz-x1>
Date:   Wed, 6 May 2020 12:06:23 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH 7/9] KVM: x86: simplify dr6 accessors in kvm_x86_ops

On Wed, May 06, 2020 at 07:10:32AM -0400, Paolo Bonzini wrote:
> kvm_x86_ops.set_dr6 is only ever called with vcpu->arch.dr6 as the
> second argument, and for both SVM and VMX the VMCB value is kept
> synchronized with vcpu->arch.dr6 on #DB; we can therefore remove the
> read accessor.
> 
> For the write accessor we can avoid the retpoline penalty on Intel
> by accepting a NULL value and just skipping the call in that case.
> 
> Suggested-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

(I think this patch and the previous one seem to be the same as the previous
 version.  Anyway...)

Reviewed-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu