Hi Brijesh:
We find this patch breaks AMD SEV support in the Hyper-V Isolation
VM. Hyper-V code also uses sev_es_ghcb_hv_call() to read or write msr
value. The sev_es_check_cpu_features() isn't called in the Hyper-V code
and so the ghcb_version is always 0. Could you add a new parameter
ghcb_version for sev_es_ghcb_hv_call() and then caller may input
ghcb_version?
Thanks. On 11/11/2021 6:06 AM, 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@xxxxxxx> --- arch/x86/include/asm/sev.h | 2 +- arch/x86/kernel/sev-shared.c | 17 ++++++++++++++--- 2 files changed, 15 insertions(+), 4 deletions(-) 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 0ULLdiff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.cindex 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);
