Messages in this thread |  | | Date | Tue, 7 Dec 2021 20:51:53 +0800 | Subject | Re: [PATCH v7 09/45] x86/sev: Save the negotiated GHCB version | From | Tianyu Lan <> |
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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@amd.com> > --- > 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 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); >
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