[PATCH v6 07/42] x86/sev: Add support for hypervisor feature VMGEXIT

[Brijesh Singh <brijesh.singh@xxxxxxx>]

Version 2 of GHCB specification introduced advertisement of a features
that are supported by the hypervisor. Add support to query the HV
features on boot.

Version 2 of GHCB specification adds several new NAEs, most of them are
optional except the hypervisor feature. Now that hypervisor feature NAE
is implemented, so bump the GHCB maximum support protocol version.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 arch/x86/include/asm/sev-common.h |  3 +++
 arch/x86/include/asm/sev.h        |  2 +-
 arch/x86/include/uapi/asm/svm.h   |  2 ++
 arch/x86/kernel/sev-shared.c      | 30 ++++++++++++++++++++++++++++++
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 3278ee578937..891569c07ed7 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -60,6 +60,9 @@
 /* GHCB Hypervisor Feature Request/Response */
 #define GHCB_MSR_HV_FT_REQ		0x080
 #define GHCB_MSR_HV_FT_RESP		0x081
+#define GHCB_MSR_HV_FT_RESP_VAL(v)			\
+	/* GHCBData[63:12] */				\
+	(((u64)(v) & GENMASK_ULL(63, 12)) >> 12)
 
 #define GHCB_MSR_TERM_REQ		0x100
 #define GHCB_MSR_TERM_REASON_SET_POS	12
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 7ec91b1359df..134a7c9d91b6 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -13,7 +13,7 @@
 #include <asm/sev-common.h>
 
 #define GHCB_PROTOCOL_MIN	1ULL
-#define GHCB_PROTOCOL_MAX	1ULL
+#define GHCB_PROTOCOL_MAX	2ULL
 #define GHCB_DEFAULT_USAGE	0ULL
 
 #define	VMGEXIT()			{ asm volatile("rep; vmmcall\n\r"); }
diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index efa969325ede..b0ad00f4c1e1 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -108,6 +108,7 @@
 #define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005
 #define SVM_VMGEXIT_SET_AP_JUMP_TABLE		0
 #define SVM_VMGEXIT_GET_AP_JUMP_TABLE		1
+#define SVM_VMGEXIT_HV_FEATURES			0x8000fffd
 #define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffff
 
 /* Exit code reserved for hypervisor/software use */
@@ -218,6 +219,7 @@
 	{ SVM_VMGEXIT_NMI_COMPLETE,	"vmgexit_nmi_complete" }, \
 	{ SVM_VMGEXIT_AP_HLT_LOOP,	"vmgexit_ap_hlt_loop" }, \
 	{ SVM_VMGEXIT_AP_JUMP_TABLE,	"vmgexit_ap_jump_table" }, \
+	{ SVM_VMGEXIT_HV_FEATURES,	"vmgexit_hypervisor_feature" }, \
 	{ SVM_EXIT_ERR,         "invalid_guest_state" }
 
 
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 0eb22528ec87..8ee27d07c1cd 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -23,6 +23,9 @@
  */
 static u16 __ro_after_init ghcb_version;
 
+/* Bitmap of SEV features supported by the hypervisor */
+static u64 __ro_after_init sev_hv_features;
+
 static bool __init sev_es_check_cpu_features(void)
 {
 	if (!has_cpuflag(X86_FEATURE_RDRAND)) {
@@ -48,6 +51,30 @@ static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
 		asm volatile("hlt\n" : : : "memory");
 }
 
+/*
+ * The hypervisor features are available from GHCB version 2 onward.
+ */
+static bool get_hv_features(void)
+{
+	u64 val;
+
+	sev_hv_features = 0;
+
+	if (ghcb_version < 2)
+		return false;
+
+	sev_es_wr_ghcb_msr(GHCB_MSR_HV_FT_REQ);
+	VMGEXIT();
+
+	val = sev_es_rd_ghcb_msr();
+	if (GHCB_RESP_CODE(val) != GHCB_MSR_HV_FT_RESP)
+		return false;
+
+	sev_hv_features = GHCB_MSR_HV_FT_RESP_VAL(val);
+
+	return true;
+}
+
 static bool sev_es_negotiate_protocol(void)
 {
 	u64 val;
@@ -66,6 +93,9 @@ static bool sev_es_negotiate_protocol(void)
 
 	ghcb_version = min_t(size_t, GHCB_MSR_PROTO_MAX(val), GHCB_PROTOCOL_MAX);
 
+	if (!get_hv_features())
+		return false;
+
 	return true;
 }
 
-- 
2.25.1