The following commit has been merged into the x86/sev branch of tip: Commit-ID: 30612045e69d088f1effd748048ebb0e282984ec Gitweb: https://git.kernel.org/tip/30612045e69d088f1effd748048ebb0e282984ec Author: Michael Roth <michael.roth@xxxxxxx> AuthorDate: Mon, 07 Mar 2022 15:33:49 -06:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 07 Apr 2022 16:47:12 +02:00 x86/sev: Use firmware-validated CPUID for SEV-SNP guests SEV-SNP guests will be provided the location of special 'secrets' and 'CPUID' pages via the Confidential Computing blob. This blob is provided to the run-time kernel either through a boot_params field that was initialized by the boot/compressed kernel, or via a setup_data structure as defined by the Linux Boot Protocol. Locate the Confidential Computing blob from these sources and, if found, use the provided CPUID page/table address to create a copy that the run-time kernel will use when servicing CPUID instructions via a #VC handler. 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/20220307213356.2797205-40-brijesh.singh@xxxxxxx --- arch/x86/boot/compressed/sev.c | 37 +--------------------------------- arch/x86/kernel/sev-shared.c | 37 +++++++++++++++++++++++++++++++++- arch/x86/kernel/sev.c | 24 +++++++++++++++++++++- 3 files changed, 61 insertions(+), 37 deletions(-) diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index 82079ce..52f989f 100644 --- a/arch/x86/boot/compressed/sev.c +++ b/arch/x86/boot/compressed/sev.c @@ -382,43 +382,6 @@ found_cc_info: } /* - * Initialize the kernel's copy of the SNP CPUID table, and set up the - * pointer that will be used to access it. - * - * Maintaining a direct mapping of the SNP CPUID table used by firmware would - * be possible as an alternative, but the approach is brittle since the - * mapping needs to be updated in sync with all the changes to virtual memory - * layout and related mapping facilities throughout the boot process. - */ -static void setup_cpuid_table(const struct cc_blob_sev_info *cc_info) -{ - const struct snp_cpuid_table *cpuid_table_fw, *cpuid_table; - int i; - - if (!cc_info || !cc_info->cpuid_phys || cc_info->cpuid_len < PAGE_SIZE) - sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID); - - cpuid_table_fw = (const struct snp_cpuid_table *)cc_info->cpuid_phys; - if (!cpuid_table_fw->count || cpuid_table_fw->count > SNP_CPUID_COUNT_MAX) - sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID); - - cpuid_table = snp_cpuid_get_table(); - memcpy((void *)cpuid_table, cpuid_table_fw, sizeof(*cpuid_table)); - - /* Initialize CPUID ranges for range-checking. */ - for (i = 0; i < cpuid_table->count; i++) { - const struct snp_cpuid_fn *fn = &cpuid_table->fn[i]; - - if (fn->eax_in == 0x0) - cpuid_std_range_max = fn->eax; - else if (fn->eax_in == 0x40000000) - cpuid_hyp_range_max = fn->eax; - else if (fn->eax_in == 0x80000000) - cpuid_ext_range_max = fn->eax; - } -} - -/* * Indicate SNP based on presence of SNP-specific CC blob. Subsequent checks * will verify the SNP CPUID/MSR bits. */ diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c index a7a1c0f..2b4270d 100644 --- a/arch/x86/kernel/sev-shared.c +++ b/arch/x86/kernel/sev-shared.c @@ -964,3 +964,40 @@ static struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp) return NULL; } + +/* + * Initialize the kernel's copy of the SNP CPUID table, and set up the + * pointer that will be used to access it. + * + * Maintaining a direct mapping of the SNP CPUID table used by firmware would + * be possible as an alternative, but the approach is brittle since the + * mapping needs to be updated in sync with all the changes to virtual memory + * layout and related mapping facilities throughout the boot process. + */ +static void __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info) +{ + const struct snp_cpuid_table *cpuid_table_fw, *cpuid_table; + int i; + + if (!cc_info || !cc_info->cpuid_phys || cc_info->cpuid_len < PAGE_SIZE) + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID); + + cpuid_table_fw = (const struct snp_cpuid_table *)cc_info->cpuid_phys; + if (!cpuid_table_fw->count || cpuid_table_fw->count > SNP_CPUID_COUNT_MAX) + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID); + + cpuid_table = snp_cpuid_get_table(); + memcpy((void *)cpuid_table, cpuid_table_fw, sizeof(*cpuid_table)); + + /* Initialize CPUID ranges for range-checking. */ + for (i = 0; i < cpuid_table->count; i++) { + const struct snp_cpuid_fn *fn = &cpuid_table->fn[i]; + + if (fn->eax_in == 0x0) + cpuid_std_range_max = fn->eax; + else if (fn->eax_in == 0x40000000) + cpuid_hyp_range_max = fn->eax; + else if (fn->eax_in == 0x80000000) + cpuid_ext_range_max = fn->eax; + } +} diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 692da7b..c873372 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -34,6 +34,7 @@ #include <asm/cpu.h> #include <asm/apic.h> #include <asm/cpuid.h> +#include <asm/cmdline.h> #define DR7_RESET_VALUE 0x400 @@ -2025,6 +2026,8 @@ bool __init snp_init(struct boot_params *bp) if (!cc_info) return false; + setup_cpuid_table(cc_info); + /* * The CC blob will be used later to access the secrets page. Cache * it here like the boot kernel does. @@ -2038,3 +2041,24 @@ void __init snp_abort(void) { sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED); } + +/* + * It is useful from an auditing/testing perspective to provide an easy way + * for the guest owner to know that the CPUID table has been initialized as + * expected, but that initialization happens too early in boot to print any + * sort of indicator, and there's not really any other good place to do it, + * so do it here. + */ +static int __init report_cpuid_table(void) +{ + const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table(); + + if (!cpuid_table->count) + return 0; + + pr_info("Using SNP CPUID table, %d entries present.\n", + cpuid_table->count); + + return 0; +} +arch_initcall(report_cpuid_table);
![]() |