linux-kernel - [PATCH v4 7/7] x86/cpu, kvm: Propagate the AMD Automatic IBRS feature to the guest

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Date:   Wed, 30 Nov 2022 19:50:03 -0600
From:   Kim Phillips <kim.phillips@....com>
To:     <x86@...nel.org>
CC:     Kim Phillips <kim.phillips@....com>,
        Babu Moger <Babu.Moger@....com>,
        Borislav Petkov <bp@...en8.de>, Borislav Petkov <bp@...e.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Alexey Kardashevskiy <aik@....com>, <kvm@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v4 7/7] x86/cpu, kvm: Propagate the AMD Automatic IBRS feature to the guest

Add the AMD Automatic IBRS feature bit to those being
propagated to the guest, and enable the guest EFER bit.

Signed-off-by: Kim Phillips <kim.phillips@....com>
---
 arch/x86/kvm/cpuid.c         | 2 +-
 arch/x86/kvm/reverse_cpuid.h | 2 ++
 arch/x86/kvm/svm/svm.c       | 3 +++
 arch/x86/kvm/x86.c           | 3 +++
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index dd0fe79521eb..0ed3ad3e9341 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -732,7 +732,7 @@ void kvm_set_cpu_caps(void)
 
 	kvm_cpu_cap_init_scattered(CPUID_8000_0021_EAX,
 		SF(NO_NESTED_DATA_BP) | SF(LFENCE_RDTSC) | 0 /* SmmPgCfgLock */ |
-		SF(NULL_SEL_CLR_BASE) | 0 /* PrefetchCtlMsr */
+		SF(NULL_SEL_CLR_BASE) | SF(AUTOIBRS) | 0 /* PrefetchCtlMsr */
 	);
 	if (cpu_feature_enabled(X86_FEATURE_LFENCE_RDTSC))
 		kvm_cpu_cap_set(X86_FEATURE_LFENCE_RDTSC);
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 184614e27d5b..0bf02c02bb0a 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -30,6 +30,7 @@ enum kvm_only_cpuid_leafs {
 #define KVM_X86_FEATURE_NO_NESTED_DATA_BP	KVM_X86_FEATURE(CPUID_8000_0021_EAX, 0)
 #define KVM_X86_FEATURE_LFENCE_RDTSC		KVM_X86_FEATURE(CPUID_8000_0021_EAX, 2)
 #define KVM_X86_FEATURE_NULL_SEL_CLR_BASE	KVM_X86_FEATURE(CPUID_8000_0021_EAX, 6)
+#define KVM_X86_FEATURE_AUTOIBRS		KVM_X86_FEATURE(CPUID_8000_0021_EAX, 8)
 
 struct cpuid_reg {
 	u32 function;
@@ -89,6 +90,7 @@ static __always_inline u32 __feature_translate(int x86_feature)
 	case X86_FEATURE_NO_NESTED_DATA_BP:	return KVM_X86_FEATURE_NO_NESTED_DATA_BP;
 	case X86_FEATURE_LFENCE_RDTSC:		return KVM_X86_FEATURE_LFENCE_RDTSC;
 	case X86_FEATURE_NULL_SEL_CLR_BASE:	return KVM_X86_FEATURE_NULL_SEL_CLR_BASE;
+	case X86_FEATURE_AUTOIBRS:		return KVM_X86_FEATURE_AUTOIBRS;
 	default: break;
 	}
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4b6d2b050e57..3ac3d4cfce24 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4960,6 +4960,9 @@ static __init int svm_hardware_setup(void)
 
 	tsc_aux_uret_slot = kvm_add_user_return_msr(MSR_TSC_AUX);
 
+	if (boot_cpu_has(X86_FEATURE_AUTOIBRS))
+		kvm_enable_efer_bits(EFER_AUTOIBRS);
+
 	/* Check for pause filtering support */
 	if (!boot_cpu_has(X86_FEATURE_PAUSEFILTER)) {
 		pause_filter_count = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 490ec23c8450..db0f522fd597 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1682,6 +1682,9 @@ static int do_get_msr_feature(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
 
 static bool __kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
+	if (efer & EFER_AUTOIBRS && !guest_cpuid_has(vcpu, X86_FEATURE_AUTOIBRS))
+		return false;
+
 	if (efer & EFER_FFXSR && !guest_cpuid_has(vcpu, X86_FEATURE_FXSR_OPT))
 		return false;
 
-- 
2.34.1