linux-kernel - [PATCH 1/3] kvm: vmx: Add IA32_FLUSH

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Date:   Wed,  1 Feb 2023 08:29:03 -0500
From:   Emanuele Giuseppe Esposito <eesposit@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>,
        Ben Serebrin <serebrin@...gle.com>,
        Peter Shier <pshier@...gle.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>,
        Maxim Levitsky <mlevitsk@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>
Subject: [PATCH 1/3] kvm: vmx: Add IA32_FLUSH_CMD guest support

Expose IA32_FLUSH_CMD to the guest if the guest CPUID enumerates
support for this MSR. As with IA32_PRED_CMD, permission for
unintercepted writes to this MSR will be granted to the guest after
the first non-zero write.

Signed-off-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@...hat.com>
---
 arch/x86/kvm/vmx/nested.c |  3 ++
 arch/x86/kvm/vmx/vmx.c    | 70 +++++++++++++++++++++++++--------------
 2 files changed, 48 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 557b9c468734..075b5ade7c80 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -654,6 +654,9 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
 	nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
 					 MSR_IA32_PRED_CMD, MSR_TYPE_W);
 
+	nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
+					 MSR_IA32_FLUSH_CMD, MSR_TYPE_W);
+
 	kvm_vcpu_unmap(vcpu, &vmx->nested.msr_bitmap_map, false);
 
 	vmx->nested.force_msr_bitmap_recalc = false;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c788aa382611..9a78ea96a6d7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2133,6 +2133,39 @@ static u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated
 	return debugctl;
 }
 
+static int vmx_set_msr_ia32_cmd(struct kvm_vcpu *vcpu,
+				struct msr_data *msr_info,
+				bool guest_has_feat, u64 cmd,
+				int x86_feature_bit)
+{
+	if (!msr_info->host_initiated && !guest_has_feat)
+		return 1;
+
+	if (!(msr_info->data & ~cmd))
+		return 1;
+	if (!boot_cpu_has(x86_feature_bit))
+		return 1;
+	if (!msr_info->data)
+		return 0;
+
+	wrmsrl(msr_info->index, cmd);
+
+	/*
+	 * For non-nested:
+	 * When it's written (to non-zero) for the first time, pass
+	 * it through.
+	 *
+	 * For nested:
+	 * The handling of the MSR bitmap for L2 guests is done in
+	 * nested_vmx_prepare_msr_bitmap. We should not touch the
+	 * vmcs02.msr_bitmap here since it gets completely overwritten
+	 * in the merging.
+	 */
+	vmx_disable_intercept_for_msr(vcpu, msr_info->index, MSR_TYPE_W);
+
+	return 0;
+}
+
 /*
  * Writes msr value into the appropriate "register".
  * Returns 0 on success, non-0 otherwise.
@@ -2288,31 +2321,18 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		goto find_uret_msr;
 	case MSR_IA32_PRED_CMD:
-		if (!msr_info->host_initiated &&
-		    !guest_has_pred_cmd_msr(vcpu))
-			return 1;
-
-		if (data & ~PRED_CMD_IBPB)
-			return 1;
-		if (!boot_cpu_has(X86_FEATURE_IBPB))
-			return 1;
-		if (!data)
-			break;
-
-		wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
-
-		/*
-		 * For non-nested:
-		 * When it's written (to non-zero) for the first time, pass
-		 * it through.
-		 *
-		 * For nested:
-		 * The handling of the MSR bitmap for L2 guests is done in
-		 * nested_vmx_prepare_msr_bitmap. We should not touch the
-		 * vmcs02.msr_bitmap here since it gets completely overwritten
-		 * in the merging.
-		 */
-		vmx_disable_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W);
+		ret = vmx_set_msr_ia32_cmd(vcpu, msr_info,
+					   guest_has_pred_cmd_msr(vcpu),
+					   PRED_CMD_IBPB,
+					   X86_FEATURE_IBPB);
+		break;
+	case MSR_IA32_FLUSH_CMD:
+		bool guest_flush_l1d = guest_cpuid_has(vcpu,
+						       X86_FEATURE_FLUSH_L1D);
+		ret = vmx_set_msr_ia32_cmd(vcpu, msr_info,
+					   guest_flush_l1d,
+					   L1D_FLUSH,
+					   X86_FEATURE_FLUSH_L1D);
 		break;
 	case MSR_IA32_CR_PAT:
 		if (!kvm_pat_valid(data))
-- 
2.39.1