On Fri, Apr 30, 2021 at 07:15:58AM -0500, 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 | 15 ++++++++++++---
> 2 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index fa5cd05d3b5b..7ec91b1359df 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 6ec8b3bfd76e..48a47540b85f 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -14,6 +14,13 @@
> #define has_cpuflag(f) boot_cpu_has(f)
> #endif
>
> +/*
> + * Since feature negotitation 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 __section(".data") = 0;
Did you not see this when running checkpatch.pl on your patch?
ERROR: do not initialise statics to 0
#141: FILE: arch/x86/kernel/sev-shared.c:22:
+static u16 ghcb_version __section(".data") = 0;
> static bool __init sev_es_check_cpu_features(void)
> {
> if (!has_cpuflag(X86_FEATURE_RDRAND)) {
> @@ -54,10 +61,12 @@ 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);
How is that even supposed to work? GHCB_PROTOCOL_MAX is 1 so
ghcb_version will be always 1 when you do min_t() on values one of which
is 1.
Maybe I'm missing something...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
