From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
"Wanpeng Li" <wanpengli@tencent.com>,
"Jim Mattson" <jmattson@google.com>,
"Joerg Roedel" <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
"Reto Buerki" <reet@codelabs.ch>,
"Liran Alon" <liran.alon@oracle.com>
Subject: Re: [PATCH v2 4/8] KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest
Date: Wed, 9 Oct 2019 14:30:21 -0700 [thread overview]
Message-ID: <20191009213021.GH19952@linux.intel.com> (raw)
In-Reply-To: <aee0fe86-6a5a-680a-4147-3b68fc3718c9@redhat.com>
On Wed, Oct 09, 2019 at 10:59:10PM +0200, Paolo Bonzini wrote:
> On 09/10/19 18:38, Sean Christopherson wrote:
> > On Wed, Oct 09, 2019 at 12:40:53PM +0200, Paolo Bonzini wrote:
> >> On 27/09/19 23:45, Sean Christopherson wrote:
> >>> 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.
> >>
> >> Slightly nicer this way:
> >>
> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> >> index 8de9853d7ab6..62ab19d65efd 100644
> >> --- a/arch/x86/kvm/vmx/vmx.c
> >> +++ b/arch/x86/kvm/vmx/vmx.c
> >> @@ -1431,9 +1431,17 @@ 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;
> >> +
> >> + if (enable_unrestricted_guest) {
> >> + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail);
> >> + vmx->rflags = rflags;
> >> + vmcs_writel(GUEST_RFLAGS, rflags);
> >> + return;
> >> + }
> >> +
> >> + old_rflags = vmx_get_rflags(vcpu);
> >>
> >> - __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail);
> >> vmx->rflags = rflags;
> >> if (vmx->rmode.vm86_active) {
> >> vmx->rmode.save_rflags = rflags;
> >
> > Works for me. Do you want me to spin a v3 to incorporate this and remove
> > the open coding of the RIP/RSP accessors? Or are you planning on squashing
> > the changes as you apply?
>
> If it's okay for you I can squash it.
Squash away.
next prev parent reply other threads:[~2019-10-09 21:30 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-27 21:45 [PATCH v2 0/8] KVM: x86: nVMX GUEST_CR3 bug fix, and then some Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 1/8] KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter Sean Christopherson
2019-09-27 23:37 ` Jim Mattson
2019-09-27 21:45 ` [PATCH v2 2/8] KVM: VMX: Skip GUEST_CR3 VMREAD+VMWRITE if the VMCS is up-to-date Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 3/8] KVM: VMX: Consolidate to_vmx() usage in RFLAGS accessors Sean Christopherson
2019-09-30 8:48 ` Vitaly Kuznetsov
2019-09-27 21:45 ` [PATCH v2 4/8] KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest Sean Christopherson
2019-09-30 8:57 ` Vitaly Kuznetsov
2019-09-30 15:19 ` Sean Christopherson
2019-09-30 15:55 ` Vitaly Kuznetsov
2019-10-09 10:40 ` Paolo Bonzini
2019-10-09 16:38 ` Sean Christopherson
2019-10-09 20:59 ` Paolo Bonzini
2019-10-09 21:30 ` Sean Christopherson [this message]
2019-09-27 21:45 ` [PATCH v2 5/8] KVM: x86: Add WARNs to detect out-of-bounds register indices Sean Christopherson
2019-09-30 9:19 ` Vitaly Kuznetsov
2019-10-09 10:50 ` Paolo Bonzini
2019-10-09 16:36 ` Sean Christopherson
2019-09-27 21:45 ` [PATCH v2 6/8] KVM: x86: Fold 'enum kvm_ex_reg' definitions into 'enum kvm_reg' Sean Christopherson
2019-09-30 9:25 ` Vitaly Kuznetsov
2019-10-09 10:52 ` Paolo Bonzini
2019-10-09 11:27 ` Vitaly Kuznetsov
2019-09-27 21:45 ` [PATCH v2 7/8] KVM: x86: Add helpers to test/mark reg availability and dirtiness Sean Christopherson
2019-09-30 9:32 ` Vitaly Kuznetsov
2019-10-09 11:00 ` Paolo Bonzini
2019-09-27 21:45 ` [PATCH v2 8/8] KVM: x86: Fold decache_cr3() into cache_reg() Sean Christopherson
2019-09-30 10:58 ` Vitaly Kuznetsov
2019-09-30 15:04 ` Sean Christopherson
2019-09-30 15:27 ` Vitaly Kuznetsov
2019-09-30 15:33 ` Sean Christopherson
2019-10-09 11:03 ` Paolo Bonzini
2019-09-30 10:42 ` [PATCH v2 0/8] KVM: x86: nVMX GUEST_CR3 bug fix, and then some Reto Buerki
2019-10-29 15:03 ` Martin Lucina
2019-10-30 9:09 ` Sean Christopherson
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