linux-kernel - [RFC PATCH v3 10/10] KVM: VMX: Advertise MITI_ENUM_RETPOLINE_S

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Date: Wed, 10 Apr 2024 22:34:38 +0800
From: Chao Gao <chao.gao@...el.com>
To: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: daniel.sneddon@...ux.intel.com,
	pawan.kumar.gupta@...ux.intel.com,
	Chao Gao <chao.gao@...el.com>,
	Zhang Chen <chen.zhang@...el.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [RFC PATCH v3 10/10] KVM: VMX: Advertise MITI_ENUM_RETPOLINE_S_SUPPORT

Allow guest to report if retpoline is used in supervisor mode.

KVM will deploy RRSBA_DIS_S for guest if guest is using retpoline and
the processor enumerates RRSBA.

Signed-off-by: Zhang Chen <chen.zhang@...el.com>
Signed-off-by: Chao Gao <chao.gao@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c5ceaebd954b..235cb6ad69c0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1956,8 +1956,10 @@ static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx,
 }
 
 #define VIRTUAL_ENUMERATION_VALID_BITS	VIRT_ENUM_MITIGATION_CTRL_SUPPORT
-#define MITI_ENUM_VALID_BITS		MITI_ENUM_BHB_CLEAR_SEQ_S_SUPPORT
-#define MITI_CTRL_VALID_BITS		MITI_CTRL_BHB_CLEAR_SEQ_S_USED
+#define MITI_ENUM_VALID_BITS		(MITI_ENUM_BHB_CLEAR_SEQ_S_SUPPORT | \
+					 MITI_ENUM_RETPOLINE_S_SUPPORT)
+#define MITI_CTRL_VALID_BITS		(MITI_CTRL_BHB_CLEAR_SEQ_S_USED | \
+					 MITI_CTRL_RETPOLINE_S_USED)
 
 static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
 {
@@ -2508,6 +2510,11 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (data & ~MITI_CTRL_VALID_BITS)
 			return 1;
 
+		if (data & MITI_CTRL_RETPOLINE_S_USED &&
+		    kvm_cpu_cap_has(X86_FEATURE_RRSBA_CTRL) &&
+		    host_arch_capabilities & ARCH_CAP_RRSBA)
+			spec_ctrl_mask |= SPEC_CTRL_RRSBA_DIS_S;
+
 		if (data & MITI_CTRL_BHB_CLEAR_SEQ_S_USED &&
 		    kvm_cpu_cap_has(X86_FEATURE_BHI_CTRL) &&
 		    !(host_arch_capabilities & ARCH_CAP_BHI_NO))
-- 
2.39.3