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From: "Tian, Kevin" <kevin.tian@intel.com>
To: "Christopherson,, Sean" <seanjc@google.com>,
	"Zhong, Yang" <yang.zhong@intel.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	"shuah@kernel.org" <shuah@kernel.org>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	"jing2.liu@linux.intel.com" <jing2.liu@linux.intel.com>,
	"Liu, Jing2" <jing2.liu@intel.com>,
	"Zeng, Guang" <guang.zeng@intel.com>,
	"Wang, Wei W" <wei.w.wang@intel.com>
Subject: RE: [PATCH v4 14/21] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR
Date: Wed, 5 Jan 2022 00:23:45 +0000	[thread overview]
Message-ID: <BN9PR11MB5276F75834DB60F73B8BDD258C4B9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <YdShTDdOQISmku2H@google.com>

> 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.

  reply	other threads:[~2022-01-05  0:23 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-29 13:13 [PATCH v4 00/21] AMX Support in KVM Yang Zhong
2021-12-29 13:13 ` [PATCH v4 01/21] x86/fpu: Extend fpu_xstate_prctl() with guest permissions Yang Zhong
2021-12-29 13:13 ` [PATCH v4 02/21] x86/fpu: Prepare guest FPU for dynamically enabled FPU features Yang Zhong
2021-12-29 13:13 ` [PATCH v4 03/21] kvm: x86: Fix xstate_required_size() to follow XSTATE alignment rule Yang Zhong
2022-01-04 19:54   ` Sean Christopherson
2021-12-29 13:13 ` [PATCH v4 04/21] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Yang Zhong
2021-12-29 13:13 ` [PATCH v4 05/21] x86/fpu: Make XFD initialization in __fpstate_reset() a function argument Yang Zhong
2021-12-29 13:13 ` [PATCH v4 06/21] x86/fpu: Add guest support to xfd_enable_feature() Yang Zhong
2021-12-29 13:13 ` [PATCH v4 07/21] x86/fpu: Provide fpu_update_guest_perm_features() for guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 08/21] kvm: x86: Check and enable permitted dynamic xfeatures at KVM_SET_CPUID2 Yang Zhong
2021-12-29 16:55   ` Sean Christopherson
2021-12-30  2:28     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 09/21] x86/fpu: Provide fpu_update_guest_xfd() for IA32_XFD emulation Yang Zhong
2021-12-29 13:13 ` [PATCH v4 10/21] kvm: x86: Add emulation for IA32_XFD Yang Zhong
2022-01-04 19:32   ` Sean Christopherson
2022-01-05  0:22     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 11/21] x86/fpu: Prepare xfd_err in struct fpu_guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 12/21] kvm: x86: Intercept #NM for saving IA32_XFD_ERR Yang Zhong
2022-01-04 20:01   ` Sean Christopherson
2022-01-05  0:27     ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 13/21] kvm: x86: Emulate IA32_XFD_ERR for guest Yang Zhong
2021-12-29 13:13 ` [PATCH v4 14/21] kvm: x86: Disable RDMSR interception of IA32_XFD_ERR Yang Zhong
2022-01-04 19:34   ` Sean Christopherson
2022-01-05  0:23     ` Tian, Kevin [this message]
2021-12-29 13:13 ` [PATCH v4 15/21] kvm: x86: Add XCR0 support for Intel AMX Yang Zhong
2021-12-29 13:13 ` [PATCH v4 16/21] kvm: x86: Add CPUID " Yang Zhong
2021-12-29 13:13 ` [PATCH v4 17/21] x86/fpu: Add uabi_size to guest_fpu Yang Zhong
2021-12-29 13:13 ` [PATCH v4 18/21] kvm: x86: Add support for getting/setting expanded xstate buffer Yang Zhong
2022-01-04 19:46   ` Sean Christopherson
2022-01-04 20:45     ` Paolo Bonzini
2022-01-05  4:03       ` Tian, Kevin
2021-12-29 13:13 ` [PATCH v4 19/21] kvm: selftests: Add support for KVM_CAP_XSAVE2 Yang Zhong
2021-12-29 13:13 ` [PATCH v4 20/21] x86/fpu: Provide fpu_sync_guest_vmexit_xfd_state() Yang Zhong
2021-12-29 13:13 ` [PATCH v4 21/21] kvm: x86: Disable interception for IA32_XFD on demand Yang Zhong
2021-12-30  8:46 ` [PATCH v4 00/21] AMX Support in KVM Tian, Kevin
2022-01-04 18:36 ` Paolo Bonzini
2022-01-04 18:54   ` Sean Christopherson
2022-01-05  0:10     ` Tian, Kevin

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