[RFC PATCH 9/9] KVM: SVM: Enable Alternate Injection for an SEV-SNP guest

[Melody Wang <huibo.wang@amd.com>]

When the SVSM detects that the hypervisor supports Alternate Injection,
it can configure Alternate Injection and create APs with it enabled in
sev_features.

Add Alternate Injection support to the hypervisor advertised features

Signed-off-by: Melody Wang <huibo.wang@amd.com>
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/sev-common.h  |  1 +
 arch/x86/kvm/svm/sev.c             | 12 +++++++++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 41af7bd2473c..b2746a4d926a 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -454,6 +454,7 @@
 #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* Virtual TSC_AUX */
 #define X86_FEATURE_SME_COHERENT	(19*32+10) /* hardware-enforced cache coherency */
 #define X86_FEATURE_RESTRICTED_INJECTION (19*32+12) /* Restricted Injection */
+#define X86_FEATURE_ALTERNATE_INJECTION (19*32+13) /* Alternate Injection */
 #define X86_FEATURE_DEBUG_SWAP		(19*32+14) /* "debug_swap" SEV-ES full debug state swap support */
 #define X86_FEATURE_RMPREAD		(19*32+21) /* RMPREAD instruction */
 #define X86_FEATURE_SEGMENTED_RMP	(19*32+23) /* Segmented RMP support */
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index a09cf5690aba..62f0c3aa7549 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -145,6 +145,7 @@ enum psc_op {
 #define GHCB_HV_FT_SNP_RINJ		(BIT_ULL(2) | GHCB_HV_FT_SNP_AP_CREATION)
 #define GHCB_HV_FT_APIC_ID_LIST		BIT_ULL(4)
 #define GHCB_HV_FT_SNP_MULTI_VMPL	BIT_ULL(5)
+#define GHCB_HV_FT_SNP_ALT_INJ		BIT_ULL(9)
 
 /*
  * SNP Page State Change NAE event
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 7846d4ebb278..fd0212abc3af 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -44,6 +44,7 @@
 				 GHCB_HV_FT_SNP_AP_CREATION	| \
 				 GHCB_HV_FT_SNP_RINJ		| \
 				 GHCB_HV_FT_APIC_ID_LIST	| \
+				 GHCB_HV_FT_SNP_ALT_INJ		| \
 				 GHCB_HV_FT_SNP_MULTI_VMPL)
 
 /*
@@ -72,6 +73,10 @@ module_param_named(sev_snp, sev_snp_enabled, bool, 0444);
 static bool sev_snp_restricted_injection_enabled = true;
 module_param_named(restricted_injection, sev_snp_restricted_injection_enabled, bool, 0444);
 
+/* enable/disable SEV-SNP Alternate Injection support */
+static bool sev_snp_alternate_injection_enabled = true;
+module_param_named(alternate_injection, sev_snp_alternate_injection_enabled, bool, 0444);
+
 static unsigned int __ro_after_init nr_ciphertext_hiding_asids;
 module_param_named(ciphertext_hiding_asids, nr_ciphertext_hiding_asids, uint, 0444);
 
@@ -3242,9 +3247,14 @@ void __init sev_hardware_setup(void)
 
 	if (!sev_snp_enabled || !cpu_feature_enabled(X86_FEATURE_RESTRICTED_INJECTION))
 		sev_snp_restricted_injection_enabled = false;
+	if (!sev_snp_enabled || !cpu_feature_enabled(X86_FEATURE_ALTERNATE_INJECTION))
+		sev_snp_alternate_injection_enabled = false;
 
-	if (sev_snp_restricted_injection_enabled)
+	if (sev_snp_restricted_injection_enabled) {
 		sev_supported_vmsa_features |= SVM_SEV_FEAT_RESTRICTED_INJECTION;
+		if (sev_snp_alternate_injection_enabled)
+			sev_supported_vmsa_features |= SVM_SEV_FEAT_ALTERNATE_INJECTION;
+	}
 }
 
 void sev_hardware_unsetup(void)
-- 
2.43.0