diff mbox series

[v8,05/40] x86/sev: Save the negotiated GHCB version

Message ID 20211210154332.11526-6-brijesh.singh@amd.com (mailing list archive)
State New
Headers show
Series Add AMD Secure Nested Paging (SEV-SNP) Guest Support | expand

Commit Message

Brijesh Singh Dec. 10, 2021, 3:42 p.m. UTC 
The SEV-ES guest calls the sev_es_negotiate_protocol() to negotiate the
GHCB protocol version before establishing the GHCB. Cache the negotiated
GHCB version so that it can be used later.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/include/asm/sev.h   |  2 +-
 arch/x86/kernel/sev-shared.c | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

Comments

Venu Busireddy Dec. 14, 2021, 12:32 a.m. UTC | #1 
On 2021-12-10 09:42:57 -0600, Brijesh Singh wrote:
> The SEV-ES guest calls the sev_es_negotiate_protocol() to negotiate the
> GHCB protocol version before establishing the GHCB. Cache the negotiated
> GHCB version so that it can be used later.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>

> ---
>  arch/x86/include/asm/sev.h   |  2 +-
>  arch/x86/kernel/sev-shared.c | 17 ++++++++++++++---
>  2 files changed, 15 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ec060c433589..9b9c190e8c3b 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -12,7 +12,7 @@ 
 #include <asm/insn.h>
 #include <asm/sev-common.h>
 
-#define GHCB_PROTO_OUR		0x0001UL
+#define GHCB_PROTOCOL_MIN	1ULL
 #define GHCB_PROTOCOL_MAX	1ULL
 #define GHCB_DEFAULT_USAGE	0ULL
 
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 2abf8a7d75e5..91105f5a02a8 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -14,6 +14,15 @@ 
 #define has_cpuflag(f)	boot_cpu_has(f)
 #endif
 
+/*
+ * Since feature negotiation related variables are set early in the boot
+ * process they must reside in the .data section so as not to be zeroed
+ * out when the .bss section is later cleared.
+ *
+ * GHCB protocol version negotiated with the hypervisor.
+ */
+static u16 ghcb_version __ro_after_init;
+
 static bool __init sev_es_check_cpu_features(void)
 {
 	if (!has_cpuflag(X86_FEATURE_RDRAND)) {
@@ -51,10 +60,12 @@  static bool sev_es_negotiate_protocol(void)
 	if (GHCB_MSR_INFO(val) != GHCB_MSR_SEV_INFO_RESP)
 		return false;
 
-	if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTO_OUR ||
-	    GHCB_MSR_PROTO_MIN(val) > GHCB_PROTO_OUR)
+	if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTOCOL_MIN ||
+	    GHCB_MSR_PROTO_MIN(val) > GHCB_PROTOCOL_MAX)
 		return false;
 
+	ghcb_version = min_t(size_t, GHCB_MSR_PROTO_MAX(val), GHCB_PROTOCOL_MAX);
+
 	return true;
 }
 
@@ -127,7 +138,7 @@  enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool set_ghcb_msr,
 				   u64 exit_info_1, u64 exit_info_2)
 {
 	/* Fill in protocol and format specifiers */
-	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
+	ghcb->protocol_version = ghcb_version;
 	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
 
 	ghcb_set_sw_exit_code(ghcb, exit_code);