Commit fe60e8f6 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Use KVM-governed feature framework to track "XSAVES enabled" 



Use the governed feature framework to track if XSAVES is "enabled", i.e.
if XSAVES can be used by the guest.  Add a comment in the SVM code to
explain the very unintuitive logic of deliberately NOT checking if XSAVES
is enumerated in the guest CPUID model.

No functional change intended.

Reviewed-by: default avatarYuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20230815203653.519297-7-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 662f6815

arch/x86/include/asm/kvm_host.h

+0 −1
Original line number Diff line number Diff line
@@ -746,7 +746,6 @@ struct kvm_vcpu_arch { 
	u64 smi_count;

	bool at_instruction_boundary;

	bool tpr_access_reporting;

	bool xsaves_enabled;

	bool xfd_no_write_intercept;

	u64 ia32_xss;

	u64 microcode_version;

arch/x86/kvm/governed_features.h

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ BUILD_BUG() 
#define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x)



KVM_GOVERNED_X86_FEATURE(GBPAGES)

KVM_GOVERNED_X86_FEATURE(XSAVES)



#undef KVM_GOVERNED_X86_FEATURE

#undef KVM_GOVERNED_FEATURE

arch/x86/kvm/svm/svm.c

+14 −3
Original line number Diff line number Diff line
@@ -4244,9 +4244,20 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) 
	struct vcpu_svm *svm = to_svm(vcpu);

	struct kvm_cpuid_entry2 *best;



	vcpu->arch.xsaves_enabled = guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&

				    boot_cpu_has(X86_FEATURE_XSAVE) &&

				    boot_cpu_has(X86_FEATURE_XSAVES);

	/*

	 * SVM doesn't provide a way to disable just XSAVES in the guest, KVM

	 * can only disable all variants of by disallowing CR4.OSXSAVE from

	 * being set.  As a result, if the host has XSAVE and XSAVES, and the

	 * guest has XSAVE enabled, the guest can execute XSAVES without

	 * faulting.  Treat XSAVES as enabled in this case regardless of

	 * whether it's advertised to the guest so that KVM context switches

	 * XSS on VM-Enter/VM-Exit.  Failure to do so would effectively give

	 * the guest read/write access to the host's XSS.

	 */

	if (boot_cpu_has(X86_FEATURE_XSAVE) &&

	    boot_cpu_has(X86_FEATURE_XSAVES) &&

	    guest_cpuid_has(vcpu, X86_FEATURE_XSAVE))

		kvm_governed_feature_set(vcpu, X86_FEATURE_XSAVES);



	/* Update nrips enabled cache */

	svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) &&

arch/x86/kvm/vmx/vmx.c

+18 −18
Original line number Diff line number Diff line
@@ -4545,13 +4545,16 @@ vmx_adjust_secondary_exec_control(struct vcpu_vmx *vmx, u32 *exec_control, 
 */

#define vmx_adjust_sec_exec_control(vmx, exec_control, name, feat_name, ctrl_name, exiting)	\

({												\

	struct kvm_vcpu *__vcpu = &(vmx)->vcpu;							\

	bool __enabled;										\

												\

	if (cpu_has_vmx_##name()) {								\

		__enabled = guest_cpuid_has(&(vmx)->vcpu,		 \

					    X86_FEATURE_##feat_name);	 \

		vmx_adjust_secondary_exec_control(vmx, exec_control,	 \

			SECONDARY_EXEC_##ctrl_name, __enabled, exiting); \

		if (kvm_is_governed_feature(X86_FEATURE_##feat_name))				\

			__enabled = guest_can_use(__vcpu, X86_FEATURE_##feat_name);		\

		else										\

			__enabled = guest_cpuid_has(__vcpu, X86_FEATURE_##feat_name);		\

		vmx_adjust_secondary_exec_control(vmx, exec_control, SECONDARY_EXEC_##ctrl_name,\

						  __enabled, exiting);				\

	}											\

})
@@ -4612,10 +4615,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx) 
	if (!enable_pml || !atomic_read(&vcpu->kvm->nr_memslots_dirty_logging))

		exec_control &= ~SECONDARY_EXEC_ENABLE_PML;



	if (cpu_has_vmx_xsaves())

		vmx_adjust_secondary_exec_control(vmx, &exec_control,

						  SECONDARY_EXEC_ENABLE_XSAVES,

						  vcpu->arch.xsaves_enabled, false);

	vmx_adjust_sec_exec_feature(vmx, &exec_control, xsaves, XSAVES);



	/*

	 * RDPID is also gated by ENABLE_RDTSCP, turn on the control if either
@@ -4634,6 +4634,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx) 
						  SECONDARY_EXEC_ENABLE_RDTSCP,

						  rdpid_or_rdtscp_enabled, false);

	}



	vmx_adjust_sec_exec_feature(vmx, &exec_control, invpcid, INVPCID);



	vmx_adjust_sec_exec_exiting(vmx, &exec_control, rdrand, RDRAND);
@@ -7743,10 +7744,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) 
	 * to the guest.  XSAVES depends on CR4.OSXSAVE, and CR4.OSXSAVE can be

	 * set if and only if XSAVE is supported.

	 */

	vcpu->arch.xsaves_enabled = kvm_cpu_cap_has(X86_FEATURE_XSAVES) &&

				    boot_cpu_has(X86_FEATURE_XSAVE) &&

				    guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&

				    guest_cpuid_has(vcpu, X86_FEATURE_XSAVES);

	if (boot_cpu_has(X86_FEATURE_XSAVE) &&

	    guest_cpuid_has(vcpu, X86_FEATURE_XSAVE))

		kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_XSAVES);



	vmx_setup_uret_msrs(vmx);

arch/x86/kvm/x86.c

+2 −2
Original line number Diff line number Diff line
@@ -1015,7 +1015,7 @@ void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu) 
		if (vcpu->arch.xcr0 != host_xcr0)

			xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);



		if (vcpu->arch.xsaves_enabled &&

		if (guest_can_use(vcpu, X86_FEATURE_XSAVES) &&

		    vcpu->arch.ia32_xss != host_xss)

			wrmsrl(MSR_IA32_XSS, vcpu->arch.ia32_xss);

	}
@@ -1046,7 +1046,7 @@ void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu) 
		if (vcpu->arch.xcr0 != host_xcr0)

			xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);



		if (vcpu->arch.xsaves_enabled &&

		if (guest_can_use(vcpu, X86_FEATURE_XSAVES) &&

		    vcpu->arch.ia32_xss != host_xss)

			wrmsrl(MSR_IA32_XSS, host_xss);

	}