From: Paolo Bonzini <pbonzini@redhat.com>
To: "Sean Christopherson" <sean.j.christopherson@intel.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Cc: 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 12:40:53 +0200 [thread overview]
Message-ID: <99e57095-d855-99d7-e10e-a415c6ef13b2@redhat.com> (raw)
In-Reply-To: <20190927214523.3376-5-sean.j.christopherson@intel.com>
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;
Paolo
next prev parent reply other threads:[~2019-10-09 10:40 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 [this message]
2019-10-09 16:38 ` Sean Christopherson
2019-10-09 20:59 ` Paolo Bonzini
2019-10-09 21:30 ` Sean Christopherson
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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