[PATCH Part1 RFC v4 04/36] x86/mm: Add sev_feature_enabled() helper

Brijesh Singh
2021-07-07T18:15:51Z

The sev_feature_enabled() helper can be used by the guest to query whether
the SNP - Secure Nested Paging feature is active.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/asm/mem_encrypt.h | 8 ++++++++
arch/x86/include/asm/msr-index.h | 2 ++
arch/x86/mm/mem_encrypt.c | 14 ++++++++++++++
3 files changed, 24 insertions(+)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 8cc2fd308f65..fb857f2e72cb 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -16,6 +16,12 @@

#include <asm/bootparam.h>

+enum sev_feature_type {
+ SEV,
+ SEV_ES,
+ SEV_SNP
+};
+
#ifdef CONFIG_AMD_MEM_ENCRYPT

extern u64 sme_me_mask;
@@ -54,6 +60,7 @@ void __init sev_es_init_vc_handling(void);
bool sme_active(void);
bool sev_active(void);
bool sev_es_active(void);
+bool sev_feature_enabled(unsigned int feature_type);

#define __bss_decrypted __section(".bss..decrypted")

@@ -87,6 +94,7 @@ static inline int __init
early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }

static inline void mem_encrypt_free_decrypted_mem(void) { }
+static bool sev_feature_enabled(unsigned int feature_type) { return false; }

#define __bss_decrypted

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index a7c413432b33..37589da0282e 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -481,8 +481,10 @@
#define MSR_AMD64_SEV 0xc0010131
#define MSR_AMD64_SEV_ENABLED_BIT 0
#define MSR_AMD64_SEV_ES_ENABLED_BIT 1
+#define MSR_AMD64_SEV_SNP_ENABLED_BIT 2
#define MSR_AMD64_SEV_ENABLED BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
#define MSR_AMD64_SEV_ES_ENABLED BIT_ULL(MSR_AMD64_SEV_ES_ENABLED_BIT)
+#define MSR_AMD64_SEV_SNP_ENABLED BIT_ULL(MSR_AMD64_SEV_SNP_ENABLED_BIT)

#define MSR_AMD64_VIRT_SPEC_CTRL 0xc001011f

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index ff08dc463634..63e7799a9a86 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -389,6 +389,16 @@ bool noinstr sev_es_active(void)
return sev_status & MSR_AMD64_SEV_ES_ENABLED;
}

+bool sev_feature_enabled(unsigned int type)
+{
+ switch (type) {
+ case SEV: return sev_status & MSR_AMD64_SEV_ENABLED;
+ case SEV_ES: return sev_status & MSR_AMD64_SEV_ES_ENABLED;
+ case SEV_SNP: return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
+ default: return false;
+ }
+}
+
/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
bool force_dma_unencrypted(struct device *dev)
{
@@ -461,6 +471,10 @@ static void print_mem_encrypt_feature_info(void)
if (sev_es_active())
pr_cont(" SEV-ES");

+ /* Secure Nested Paging */
+ if (sev_feature_enabled(SEV_SNP))
+ pr_cont(" SEV-SNP");
+
pr_cont("\n");
}

--
2.17.1