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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id a14sm16815711wmm.44.2019.09.30.01.57.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Sep 2019 01:57:18 -0700 (PDT) From: Vitaly Kuznetsov To: Sean Christopherson , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Reto Buerki , Liran Alon Subject: Re: [PATCH v2 4/8] KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest In-Reply-To: <20190927214523.3376-5-sean.j.christopherson@intel.com> References: <20190927214523.3376-1-sean.j.christopherson@intel.com> <20190927214523.3376-5-sean.j.christopherson@intel.com> Date: Mon, 30 Sep 2019 10:57:17 +0200 Message-ID: <87muem40wi.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sean Christopherson writes: > Rework vmx_set_rflags() to avoid the extra code need to handle emulation > of real mode and invalid state when unrestricted guest is disabled. The > primary reason for doing so is to avoid the call to vmx_get_rflags(), > which will incur a VMREAD when RFLAGS is not already available. When > running nested VMs, the majority of calls to vmx_set_rflags() will occur > without an associated vmx_get_rflags(), i.e. when stuffing GUEST_RFLAGS > during transitions between vmcs01 and vmcs02. > > Note, vmx_get_rflags() guarantees RFLAGS is marked available. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/vmx/vmx.c | 28 ++++++++++++++++++---------- > 1 file changed, 18 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 83fe8b02b732..814d3e6d0264 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -1426,18 +1426,26 @@ unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) > void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > - unsigned long old_rflags = vmx_get_rflags(vcpu); > + unsigned long old_rflags; > > - __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); > - vmx->rflags = rflags; > - if (vmx->rmode.vm86_active) { > - vmx->rmode.save_rflags = rflags; > - rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; > + if (enable_unrestricted_guest) { > + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); > + > + vmx->rflags = rflags; > + vmcs_writel(GUEST_RFLAGS, rflags); > + } else { > + old_rflags = vmx_get_rflags(vcpu); > + > + vmx->rflags = rflags; > + if (vmx->rmode.vm86_active) { > + vmx->rmode.save_rflags = rflags; > + rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; > + } > + vmcs_writel(GUEST_RFLAGS, rflags); > + > + if ((old_rflags ^ vmx->rflags) & X86_EFLAGS_VM) > + vmx->emulation_required = emulation_required(vcpu); > } > - vmcs_writel(GUEST_RFLAGS, rflags); We're doing vmcs_writel() in both branches so it could've stayed here, right? > - > - if ((old_rflags ^ vmx->rflags) & X86_EFLAGS_VM) > - vmx->emulation_required = emulation_required(vcpu); > } > > u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu) Reviewed-by: Vitaly Kuznetsov -- Vitaly