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    SubjectRe: [PATCH Part1 RFC v3 03/22] x86/sev: Save the negotiated GHCB version
    On 2021-06-02 09:03:57 -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@amd.com>

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

    > ---
    > 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 de0e7e6c52b8..70f181f20d92 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 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.
    > + */
    > +static u16 ghcb_version __section(".data");
    > +
    > 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);
    > +
    > return true;
    > }
    >
    > @@ -101,7 +110,7 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
    > enum es_result ret;
    >
    > /* 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);
    > --
    > 2.17.1
    >

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