| Message ID | 20190507191805.9932-11-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: VMX: Reduce VMWRITEs to VMCS controls | expand |
On 07/05/19 21:18, Sean Christopherson wrote: > KVM dynamically toggles SECONDARY_EXEC_DESC to intercept (a subset of) > instructions that are subject to User-Mode Instruction Prevention, i.e. > VMCS.SECONDARY_EXEC_DESC == CR4.UMIP when emulating UMIP. Preset the > VMCS control when preparing vmcs02 to avoid unnecessarily VMWRITEs, > e.g. KVM will clear VMCS.SECONDARY_EXEC_DESC in prepare_vmcs02_early() > and then set it in vmx_set_cr4(). > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kvm/vmx/nested.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index e4d363661ae7..4b5be38cfc86 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -2057,6 +2057,11 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) > /* VMCS shadowing for L2 is emulated for now */ > exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS; > > + /* Preset *DT exiting when emulating UMIP (vmx_set_cr4()). */ > + if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated() && > + (vmcs12->guest_cr4 & X86_CR4_UMIP)) > + exec_control |= SECONDARY_EXEC_DESC; I am not sure how used this functionality is, but I guess it's not a big price to pay. However, --verbose is preferred: /* * Preset *DT exiting when emulating UMIP, so that vmx_set_cr4() * will not have to rewrite the controls just for this bit. */ Paolo > if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) > vmcs_write16(GUEST_INTR_STATUS, > vmcs12->guest_intr_status); >
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index e4d363661ae7..4b5be38cfc86 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2057,6 +2057,11 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) /* VMCS shadowing for L2 is emulated for now */ exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS; + /* Preset *DT exiting when emulating UMIP (vmx_set_cr4()). */ + if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated() && + (vmcs12->guest_cr4 & X86_CR4_UMIP)) + exec_control |= SECONDARY_EXEC_DESC; + if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) vmcs_write16(GUEST_INTR_STATUS, vmcs12->guest_intr_status);
KVM dynamically toggles SECONDARY_EXEC_DESC to intercept (a subset of) instructions that are subject to User-Mode Instruction Prevention, i.e. VMCS.SECONDARY_EXEC_DESC == CR4.UMIP when emulating UMIP. Preset the VMCS control when preparing vmcs02 to avoid unnecessarily VMWRITEs, e.g. KVM will clear VMCS.SECONDARY_EXEC_DESC in prepare_vmcs02_early() and then set it in vmx_set_cr4(). Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/vmx/nested.c | 5 +++++ 1 file changed, 5 insertions(+)