x86/boot: Add Confidential Computing type to setup_data

While launching encrypted guests, the hypervisor may need to provide
some additional information during the guest boot. When booting under an
EFI-based BIOS, the EFI configuration table contains an entry for the
confidential computing blob that contains the required information.

To support booting encrypted guests on non-EFI VMs, the hypervisor
needs to pass this additional information to the guest kernel using a
different method.

For this purpose, introduce SETUP_CC_BLOB type in setup_data to hold
the physical address of the confidential computing blob location. The
boot loader or hypervisor may choose to use this method instead of an
EFI configuration table. The CC blob location scanning should give
preference to a setup_data blob over an EFI configuration table.

In AMD SEV-SNP, the CC blob contains the address of the secrets and
CPUID pages. The secrets page includes information such as a VM to PSP
communication key and the CPUID page contains PSP-filtered CPUID values.
Define the AMD SEV confidential computing blob structure.

While at it, define the EFI GUID for the confidential computing blob.

  [ bp: Massage commit message, mark struct __packed. ]

Signed-off-by: Brijesh Singh <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: codomania

arch/x86/include/asm/sev.h

@@ -42,6 +42,24 @@ struct es_em_ctxt {
 	struct es_fault_info fi;
 };
 
+/*
+ * AMD SEV Confidential computing blob structure. The structure is
+ * defined in OVMF UEFI firmware header:
+ * https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
+ */
+#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
+struct cc_blob_sev_info {
+	u32 magic;
+	u16 version;
+	u16 reserved;
+	u64 secrets_phys;
+	u32 secrets_len;
+	u32 rsvd1;
+	u64 cpuid_phys;
+	u32 cpuid_len;
+	u32 rsvd2;
+} __packed;
+
 void do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code);
 
 static inline u64 lower_bits(u64 val, unsigned int bits)

arch/x86/include/uapi/asm/bootparam.h

@@ -10,6 +10,7 @@
 #define SETUP_EFI			4
 #define SETUP_APPLE_PROPERTIES		5
 #define SETUP_JAILHOUSE			6
+#define SETUP_CC_BLOB			7
 
 #define SETUP_INDIRECT			(1<<31)
 

include/linux/efi.h

@@ -390,6 +390,7 @@ void efi_native_runtime_setup(void);
 #define EFI_CERT_SHA256_GUID			EFI_GUID(0xc1c41626, 0x504c, 0x4092, 0xac, 0xa9, 0x41, 0xf9, 0x36, 0x93, 0x43, 0x28)
 #define EFI_CERT_X509_GUID			EFI_GUID(0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72)
 #define EFI_CERT_X509_SHA256_GUID		EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, 0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
+#define EFI_CC_BLOB_GUID			EFI_GUID(0x067b1f5f, 0xcf26, 0x44c5, 0x85, 0x54, 0x93, 0xd7, 0x77, 0x91, 0x2d, 0x42)
 
 /*
  * This GUID is used to pass to the kernel proper the struct screen_info