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([2001:b07:6468:f312:9def:34a0:b68d:9993]) by smtp.gmail.com with ESMTPSA id n3sm9523174wmc.27.2020.03.05.03.49.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Mar 2020 03:49:25 -0800 (PST) Subject: Re: [PATCH] KVM: VMX: Use wrapper macro ~RMODE_GUEST_OWNED_EFLAGS_BITS directly To: linmiaohe , rkrcmar@redhat.com, sean.j.christopherson@intel.com, vkuznets@redhat.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org References: <1583375731-18219-1-git-send-email-linmiaohe@huawei.com> From: Paolo Bonzini Message-ID: Date: Thu, 5 Mar 2020 12:49:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <1583375731-18219-1-git-send-email-linmiaohe@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/03/20 03:35, linmiaohe wrote: > (X86_EFLAGS_IOPL | X86_EFLAGS_VM) indicates the eflag bits that can not be > owned by realmode guest, i.e. ~RMODE_GUEST_OWNED_EFLAGS_BITS. ... but ~RMODE_GUEST_OWNED_EFLAGS_BITS is the bits that are owned by the host; they could be 0 or 1 and that's why the code was using X86_EFLAGS_IOPL | X86_EFLAGS_VM. I understand where ~RMODE_GUEST_OWNED_EFLAGS_BITS is better than X86_EFLAGS_IOPL | X86_EFLAGS_VM, but I cannot think of a way to express it that is the best of both worlds. Paolo Use wrapper > macro directly to make it clear and also improve readability. > > Signed-off-by: Miaohe Lin > --- > arch/x86/kvm/vmx/vmx.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 743b81642ce2..9571f8dea016 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -1466,7 +1466,7 @@ void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > vmx->rflags = rflags; > if (vmx->rmode.vm86_active) { > vmx->rmode.save_rflags = rflags; > - rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; > + rflags |= ~RMODE_GUEST_OWNED_EFLAGS_BITS; > } > vmcs_writel(GUEST_RFLAGS, rflags);