| Message ID | 20211110220731.2396491-10-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Guest Support | expand |
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);
>
On 12/7/21 7:17 AM, Borislav Petkov wrote: > On Tue, Dec 07, 2021 at 08:51:53PM +0800, Tianyu Lan wrote: >> Hi Brijesh: > > Do me a favor please and learn not to top-post on a public mailing list. > Also, take the time to read Documentation/process/ before you send > upstream patches and how to work with the community in general. > >> 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. > > If hyperv is going to expose hypervisor features, then it better report > GHCB v2. If not, then I guess < 2 or 1 or so, depending on how this is > defined. > >> Could you add a new parameter ghcb_version for sev_es_ghcb_hv_call() >> and then caller may input ghcb_version? > > No, your hypervisor needs to adhere to the spec and report proper ghcb > version. We won't be doing any accomodate-hyperv hacks. > Agreed, the HyperV support need to negotiate the GHCB version before making those HC. In the current patch, the sev_es_negotiate_protocol() will save the ghcb_version in global variable and the saved value is used during the HC. Just make sure that initial HyperV support is adhering to the specification. thanks
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);
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(-)