| Message ID | 20211229131328.12283-15-yang.zhong@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | AMX Support in KVM | expand |
On Wed, Dec 29, 2021, Yang Zhong wrote: > From: Jing Liu <jing2.liu@intel.com> > > Disable read emulation of IA32_XFD_ERR MSR if guest cpuid includes XFD. > This saves one unnecessary VM-exit in guest #NM handler, given that the > MSR is already restored with the guest value before the guest is resumed. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Jing Liu <jing2.liu@intel.com> > Signed-off-by: Yang Zhong <yang.zhong@intel.com> > --- > arch/x86/kvm/vmx/vmx.c | 6 ++++++ > arch/x86/kvm/vmx/vmx.h | 2 +- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 4e51de876085..638665b3e241 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -162,6 +162,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = { > MSR_FS_BASE, > MSR_GS_BASE, > MSR_KERNEL_GS_BASE, > + MSR_IA32_XFD_ERR, > #endif > MSR_IA32_SYSENTER_CS, > MSR_IA32_SYSENTER_ESP, > @@ -7228,6 +7229,11 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > } > } > > + if (boot_cpu_has(X86_FEATURE_XFD)) This should be kvm_cpu_cap_has(), not boot_cpu_has(). If 32-bit kernels don't suppress XFD in boot_cpu_data, then using boot_cpus_has() is wrong. And even if XFD is suppressed, using kvm_cpu_cap_has() is still preferable. > + vmx_set_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R, > + !guest_cpuid_has(vcpu, X86_FEATURE_XFD)); > + > + > set_cr4_guest_host_mask(vmx); > > vmx_write_encls_bitmap(vcpu, NULL); > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 4df2ac24ffc1..bf9d3051cd6c 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -340,7 +340,7 @@ struct vcpu_vmx { > struct lbr_desc lbr_desc; > > /* Save desired MSR intercept (read: pass-through) state */ > -#define MAX_POSSIBLE_PASSTHROUGH_MSRS 13 > +#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14 > struct { > DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS); > DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
> From: Sean Christopherson <seanjc@google.com> > Sent: Wednesday, January 5, 2022 3:35 AM > > On Wed, Dec 29, 2021, Yang Zhong wrote: > > From: Jing Liu <jing2.liu@intel.com> > > > > Disable read emulation of IA32_XFD_ERR MSR if guest cpuid includes XFD. > > This saves one unnecessary VM-exit in guest #NM handler, given that the > > MSR is already restored with the guest value before the guest is resumed. > > > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > > Signed-off-by: Jing Liu <jing2.liu@intel.com> > > Signed-off-by: Yang Zhong <yang.zhong@intel.com> > > --- > > arch/x86/kvm/vmx/vmx.c | 6 ++++++ > > arch/x86/kvm/vmx/vmx.h | 2 +- > > 2 files changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > > index 4e51de876085..638665b3e241 100644 > > --- a/arch/x86/kvm/vmx/vmx.c > > +++ b/arch/x86/kvm/vmx/vmx.c > > @@ -162,6 +162,7 @@ static u32 > vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = { > > MSR_FS_BASE, > > MSR_GS_BASE, > > MSR_KERNEL_GS_BASE, > > + MSR_IA32_XFD_ERR, > > #endif > > MSR_IA32_SYSENTER_CS, > > MSR_IA32_SYSENTER_ESP, > > @@ -7228,6 +7229,11 @@ static void vmx_vcpu_after_set_cpuid(struct > kvm_vcpu *vcpu) > > } > > } > > > > + if (boot_cpu_has(X86_FEATURE_XFD)) > > This should be kvm_cpu_cap_has(), not boot_cpu_has(). If 32-bit kernels > don't > suppress XFD in boot_cpu_data, then using boot_cpus_has() is wrong. And > even if > XFD is suppressed, using kvm_cpu_cap_has() is still preferable. > Make sense.
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 4e51de876085..638665b3e241 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -162,6 +162,7 @@ static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = { MSR_FS_BASE, MSR_GS_BASE, MSR_KERNEL_GS_BASE, + MSR_IA32_XFD_ERR, #endif MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, @@ -7228,6 +7229,11 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) } } + if (boot_cpu_has(X86_FEATURE_XFD)) + vmx_set_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R, + !guest_cpuid_has(vcpu, X86_FEATURE_XFD)); + + set_cr4_guest_host_mask(vmx); vmx_write_encls_bitmap(vcpu, NULL); diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 4df2ac24ffc1..bf9d3051cd6c 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -340,7 +340,7 @@ struct vcpu_vmx { struct lbr_desc lbr_desc; /* Save desired MSR intercept (read: pass-through) state */ -#define MAX_POSSIBLE_PASSTHROUGH_MSRS 13 +#define MAX_POSSIBLE_PASSTHROUGH_MSRS 14 struct { DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS); DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);