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x86/sev: Save the negotiated GHCB version 

The SEV-ES guest calls 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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-12-brijesh.singh@amd.com
This commit is contained in:
Brijesh Singh 2022-02-09 12:10:05 -06:00 committed by Borislav Petkov
parent 6c0f74d678
commit 2ea29c5abb
2 changed files with 15 additions and 4 deletions
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2
arch/x86/include/asm/sev.h
View File

@ -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

17
arch/x86/kernel/sev-shared.c
View File

@ -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);