[PATCH] x86/sev: Return an error on a returned non-zero SW_EXITINFO1[31:0]

[Tom Lendacky <thomas.lendacky@amd.com>]

After returning from a VMGEXIT NAE event, SW_EXITINFO1[31:0] is checked
for a value of 1, which indicates an error and that SW_EXITINFO2 contains
exception information. However, future versions of the GHCB specification
may define new values for SW_EXITINFO1[31:0], so really any non-zero value
should be treated as an error.

Fixes: 597cfe48212a ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler")
Cc: <stable@vger.kernel.org> # 5.10+
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kernel/sev-shared.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 34f20e08dc46..ff1e82ff52d9 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -130,6 +130,8 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 		} else {
 			ret = ES_VMM_ERROR;
 		}
+	} else if (ghcb->save.sw_exit_info_1 & 0xffffffff) {
+		ret = ES_VMM_ERROR;
 	} else {
 		ret = ES_OK;
 	}
-- 
2.33.0