[tip: x86/boot] x86/sev: Don't hang but terminate on failure to remap SVSM CA

[tip-bot2 for Ard Biesheuvel]

The following commit has been merged into the x86/boot branch of tip:

Commit-ID:     893930143440eb5e3ea8f69cb51ab2e61e15c4e1
Gitweb:        https://git.kernel.org/tip/893930143440eb5e3ea8f69cb51ab2e61e15c4e1
Author:        Ard Biesheuvel <ardb@xxxxxxxxxx>
AuthorDate:    Mon, 06 Jan 2025 16:57:46 +01:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 07 Jan 2025 11:47:40 +01:00

x86/sev: Don't hang but terminate on failure to remap SVSM CA

Commit

  09d35045cd0f  ("x86/sev: Avoid WARN()s and panic()s in early boot code")

replaced a panic() that could potentially hit before the kernel is even
mapped with a deadloop, to ensure that execution does not proceed when the
condition in question hits.

As Tom suggests, it is better to terminate and return to the hypervisor
in this case, using a newly invented failure code to describe the
failure condition.

Suggested-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Link: https://lore.kernel.org/all/9ce88603-20ca-e644-2d8a-aeeaf79cde69@xxxxxxx
---
 arch/x86/coco/sev/core.c          | 4 ++--
 arch/x86/include/asm/sev-common.h | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 499b419..8689854 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -2356,8 +2356,8 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
 	call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
 	call.rcx = pa;
 	ret = svsm_perform_call_protocol(&call);
-	while (ret)
-		cpu_relax(); /* too early to panic */
+	if (ret)
+		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CA_REMAP_FAIL);
 
 	RIP_REL_REF(boot_svsm_caa) = (struct svsm_ca *)pa;
 	RIP_REL_REF(boot_svsm_caa_pa) = pa;
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 50f5666..577b64d 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -206,6 +206,7 @@ struct snp_psc_desc {
 #define GHCB_TERM_NO_SVSM		7	/* SVSM is not advertised in the secrets page */
 #define GHCB_TERM_SVSM_VMPL0		8	/* SVSM is present but has set VMPL to 0 */
 #define GHCB_TERM_SVSM_CAA		9	/* SVSM is present but CAA is not page aligned */
+#define GHCB_TERM_SVSM_CA_REMAP_FAIL	10	/* SVSM is present but CA could not be remapped */
 
 #define GHCB_RESP_CODE(v)		((v) & GHCB_MSR_INFO_MASK)