[PATCH 5/7] x86/sev: Add a function to contain all SEV-specific setup operations

[Melody Wang]

To make the code clean in the boot phase, add a sev_prepare() wrapper
which contains early SEV-specific checks in order to have all that code
in a single place.

No functional changes.

Signed-off-by: Melody Wang <huibo.wang@xxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 arch/x86/boot/compressed/sev.c          |  9 +++++++++
 arch/x86/include/asm/sev.h              |  3 +++
 drivers/firmware/efi/libstub/x86-stub.c | 20 ++++++--------------
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index fc2029746c50..655291a03dcc 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -511,3 +511,12 @@ bool early_is_sevsnp_guest(void)
 	}
 	return true;
 }
+
+u64 sev_prepare(void)
+{
+	u64 unsupported = snp_get_unsupported_features(sev_get_status());
+	if (unsupported)
+		return unsupported;
+
+	return 0;
+}
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 491a891a7694..b430c1aab403 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -613,6 +613,8 @@ static inline void sev_evict_cache(void *va, int npages)
 	}
 }
 
+u64 sev_prepare(void);
+
 #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
 #define snp_vmpl 0
@@ -661,6 +663,7 @@ static inline enum es_result savic_register_gpa(u64 gpa) { return ES_UNSUPPORTED
 static inline enum es_result savic_unregister_gpa(u64 *gpa) { return ES_UNSUPPORTED; }
 static inline void hvs_ghcb_msr_write(u32 reg, u64 value) { }
 static inline u64 hvs_ghcb_msr_read(u32 reg) { return 0; }
+static inline u64 sev_prepare(void) { return 0; }
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */
 
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index cef32e2c82d8..95fa16fc9887 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -783,19 +783,6 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
 	return EFI_SUCCESS;
 }
 
-static bool have_unsupported_snp_features(void)
-{
-	u64 unsupported;
-
-	unsupported = snp_get_unsupported_features(sev_get_status());
-	if (unsupported) {
-		efi_err("Unsupported SEV-SNP features detected: 0x%llx\n",
-			unsupported);
-		return true;
-	}
-	return false;
-}
-
 static void efi_get_seed(void *seed, int size)
 {
 	efi_get_random_bytes(size, seed);
@@ -919,6 +906,7 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 	unsigned long kernel_entry;
 	struct setup_header *hdr;
 	efi_status_t status;
+	u64 unsup_feats;
 
 	efi_system_table = sys_table_arg;
 	/* Check if we were booted by the EFI firmware */
@@ -933,8 +921,12 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 
 	hdr = &boot_params->hdr;
 
-	if (have_unsupported_snp_features())
+	unsup_feats = sev_prepare();
+	if (unsup_feats) {
+		efi_err("Unsupported SEV-SNP features detected: 0x%llx\n",
+			unsup_feats);
 		efi_exit(handle, EFI_UNSUPPORTED);
+	}
 
 	if (IS_ENABLED(CONFIG_EFI_DXE_MEM_ATTRIBUTES)) {
 		efi_dxe_table = get_efi_config_table(EFI_DXE_SERVICES_TABLE_GUID);
-- 
2.43.0