linux-kernel - Re: [PATCH] KVM: cleanup DR6/DR7 reserved bits checks

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Date:   Tue, 2 Feb 2021 10:27:27 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: cleanup DR6/DR7 reserved bits checks

On Tue, Feb 02, 2021, Paolo Bonzini wrote:
> kvm_dr6_valid and kvm_dr7_valid check that bits 63:32 are zero.  Using
> them makes it easier to review the code for inconsistencies.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 97674204bf44..e52e38f8c74d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4414,9 +4414,9 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
>  	if (dbgregs->flags)
>  		return -EINVAL;
>  
> -	if (dbgregs->dr6 & ~0xffffffffull)

Oof, you weren't kidding.

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

> +	if (!kvm_dr6_valid(dbgregs->dr6))
>  		return -EINVAL;
> -	if (dbgregs->dr7 & ~0xffffffffull)
> +	if (!kvm_dr7_valid(dbgregs->dr7))
>  		return -EINVAL;
>  
>  	memcpy(vcpu->arch.db, dbgregs->db, sizeof(vcpu->arch.db));
> -- 
> 2.26.2
>