x86/compressed: Add SEV-SNP feature detection/setup

Initial/preliminary detection of SEV-SNP is done via the Confidential
Computing blob. Check for it prior to the normal SEV/SME feature
initialization, and add some sanity checks to confirm it agrees with
SEV-SNP CPUID/MSR bits.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-35-brijesh.singh@amd.com

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 7a9cfbc..2a94bb7 100644 (file)
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -274,6 +274,13 @@ void sev_enable(struct boot_params *bp)
 {
        unsigned int eax, ebx, ecx, edx;
        struct msr m;
+       bool snp;
+
+       /*
+        * Setup/preliminary detection of SNP. This will be sanity-checked
+        * against CPUID/MSR values later.
+        */
+       snp = snp_init(bp);
 
        /* Check for the SME/SEV support leaf */
        eax = 0x80000000;
@@ -294,8 +301,11 @@ void sev_enable(struct boot_params *bp)
        ecx = 0;
        native_cpuid(&eax, &ebx, &ecx, &edx);
        /* Check whether SEV is supported */
-       if (!(eax & BIT(1)))
+       if (!(eax & BIT(1))) {
+               if (snp)
+                       error("SEV-SNP support indicated by CC blob, but not CPUID.");
                return;
+       }
 
        /* Set the SME mask if this is an SEV guest. */
        boot_rdmsr(MSR_AMD64_SEV, &m);
@@ -320,5 +330,105 @@ void sev_enable(struct boot_params *bp)
                enforce_vmpl0();
        }
 
+       if (snp && !(sev_status & MSR_AMD64_SEV_SNP_ENABLED))
+               error("SEV-SNP supported indicated by CC blob, but not SEV status MSR.");
+
        sme_me_mask = BIT_ULL(ebx & 0x3f);
 }
+
+/* Search for Confidential Computing blob in the EFI config table. */
+static struct cc_blob_sev_info *find_cc_blob_efi(struct boot_params *bp)
+{
+       unsigned long cfg_table_pa;
+       unsigned int cfg_table_len;
+       int ret;
+
+       ret = efi_get_conf_table(bp, &cfg_table_pa, &cfg_table_len);
+       if (ret)
+               return NULL;
+
+       return (struct cc_blob_sev_info *)efi_find_vendor_table(bp, cfg_table_pa,
+                                                               cfg_table_len,
+                                                               EFI_CC_BLOB_GUID);
+}
+
+struct cc_setup_data {
+       struct setup_data header;
+       u32 cc_blob_address;
+};
+
+/*
+ * Search for a Confidential Computing blob passed in as a setup_data entry
+ * via the Linux Boot Protocol.
+ */
+static struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp)
+{
+       struct cc_setup_data *sd = NULL;
+       struct setup_data *hdr;
+
+       hdr = (struct setup_data *)bp->hdr.setup_data;
+
+       while (hdr) {
+               if (hdr->type == SETUP_CC_BLOB) {
+                       sd = (struct cc_setup_data *)hdr;
+                       return (struct cc_blob_sev_info *)(unsigned long)sd->cc_blob_address;
+               }
+               hdr = (struct setup_data *)hdr->next;
+       }
+
+       return NULL;
+}
+
+/*
+ * Initial set up of SNP relies on information provided by the
+ * Confidential Computing blob, which can be passed to the boot kernel
+ * by firmware/bootloader in the following ways:
+ *
+ * - via an entry in the EFI config table
+ * - via a setup_data structure, as defined by the Linux Boot Protocol
+ *
+ * Scan for the blob in that order.
+ */
+static struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
+{
+       struct cc_blob_sev_info *cc_info;
+
+       cc_info = find_cc_blob_efi(bp);
+       if (cc_info)
+               goto found_cc_info;
+
+       cc_info = find_cc_blob_setup_data(bp);
+       if (!cc_info)
+               return NULL;
+
+found_cc_info:
+       if (cc_info->magic != CC_BLOB_SEV_HDR_MAGIC)
+               sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
+
+       return cc_info;
+}
+
+/*
+ * Indicate SNP based on presence of SNP-specific CC blob. Subsequent checks
+ * will verify the SNP CPUID/MSR bits.
+ */
+bool snp_init(struct boot_params *bp)
+{
+       struct cc_blob_sev_info *cc_info;
+
+       if (!bp)
+               return false;
+
+       cc_info = find_cc_blob(bp);
+       if (!cc_info)
+               return false;
+
+       /*
+        * Pass run-time kernel a pointer to CC info via boot_params so EFI
+        * config table doesn't need to be searched again during early startup
+        * phase.
+        */
+       bp->cc_blob_address = (u32)(unsigned long)cc_info;
+
+       return true;
+}

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 8c934bd..31b3b10 100644 (file)
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -11,6 +11,7 @@
 #include <linux/types.h>
 #include <asm/insn.h>
 #include <asm/sev-common.h>
+#include <asm/bootparam.h>
 
 #define GHCB_PROTOCOL_MIN      1ULL
 #define GHCB_PROTOCOL_MAX      2ULL
@@ -151,6 +152,7 @@ void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op
 void snp_set_memory_shared(unsigned long vaddr, unsigned int npages);
 void snp_set_memory_private(unsigned long vaddr, unsigned int npages);
 void snp_set_wakeup_secondary_cpu(void);
+bool snp_init(struct boot_params *bp);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -168,6 +170,7 @@ static inline void __init snp_prep_memory(unsigned long paddr, unsigned int sz,
 static inline void snp_set_memory_shared(unsigned long vaddr, unsigned int npages) { }
 static inline void snp_set_memory_private(unsigned long vaddr, unsigned int npages) { }
 static inline void snp_set_wakeup_secondary_cpu(void) { }
+static inline bool snp_init(struct boot_params *bp) { return false; }
 #endif
 
 #endif