The following commit has been merged into the x86/sev branch of tip: Commit-ID: c01fce9cef8491974f7f007f90281f1608400768 Gitweb: https://git.kernel.org/tip/c01fce9cef8491974f7f007f90281f1608400768 Author: Michael Roth <michael.roth@xxxxxxx> AuthorDate: Thu, 24 Feb 2022 10:56:14 -06:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 07 Apr 2022 16:47:11 +02:00 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@xxxxxxx> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lore.kernel.org/r/20220307213356.2797205-35-brijesh.singh@xxxxxxx --- arch/x86/boot/compressed/sev.c | 112 +++++++++++++++++++++++++++++++- arch/x86/include/asm/sev.h | 3 +- 2 files changed, 114 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index 7a9cfbc..2a94bb7 100644 --- 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 --- 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
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