x86/sev: Check for the presence of an SVSM in the SNP secrets page

During early boot phases, check for the presence of an SVSM when running
as an SEV-SNP guest.

An SVSM is present if not running at VMPL0 and the 64-bit value at offset
0x148 into the secrets page is non-zero. If an SVSM is present, save the
SVSM Calling Area address (CAA), located at offset 0x150 into the secrets
page, and set the VMPL level of the guest, which should be non-zero, to
indicate the presence of an SVSM.

  [ bp: Touchups. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/9d3fe161be93d4ea60f43c2a3f2c311fe708b63b.1717600736.git.thomas.lendacky@amd.com

1 files changed, 32 insertions, 1 deletions

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ca20cc4e5826..2a44376f9f91 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -152,9 +152,32 @@ struct snp_secrets_page {
 	u8 vmpck2[VMPCK_KEY_LEN];
 	u8 vmpck3[VMPCK_KEY_LEN];
 	struct secrets_os_area os_area;
-	u8 rsvd3[3840];
+
+	u8 vmsa_tweak_bitmap[64];
+
+	/* SVSM fields */
+	u64 svsm_base;
+	u64 svsm_size;
+	u64 svsm_caa;
+	u32 svsm_max_version;
+	u8 svsm_guest_vmpl;
+	u8 rsvd3[3];
+
+	/* Remainder of page */
+	u8 rsvd4[3744];
 } __packed;
 
+/*
+ * The SVSM Calling Area (CA) related structures.
+ */
+struct svsm_ca {
+	u8 call_pending;
+	u8 mem_available;
+	u8 rsvd1[6];
+
+	u8 svsm_buffer[PAGE_SIZE - 8];
+};
+
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 extern void __sev_es_ist_enter(struct pt_regs *regs);
 extern void __sev_es_ist_exit(void);
@@ -181,6 +204,14 @@ static __always_inline void sev_es_nmi_complete(void)
 extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
 extern void sev_enable(struct boot_params *bp);
 
+/*
+ * RMPADJUST modifies the RMP permissions of a page of a lesser-
+ * privileged (numerically higher) VMPL.
+ *
+ * If the guest is running at a higher-privilege than the privilege
+ * level the instruction is targeting, the instruction will succeed,
+ * otherwise, it will fail.
+ */
 static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs)
 {
 	int rc;