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