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Date: Fri, 08 Apr 2022 09:08:43 -0000
From: "tip-bot2 for Michael Roth" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Michael Roth <michael.roth@....com>,
Brijesh Singh <brijesh.singh@....com>,
Borislav Petkov <bp@...e.de>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/sev] x86/sev: Use firmware-validated CPUID for SEV-SNP guests
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@....com>
AuthorDate: Mon, 07 Mar 2022 15:33:49 -06:00
Committer: Borislav Petkov <bp@...e.de>
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@....com>
Signed-off-by: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-40-brijesh.singh@amd.com
---
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);
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