The following commit has been merged into the x86/sev branch of tip:
Commit-ID: 99ef9f59847cab1f9091cd4b9d7efbee0ae4fc86
Gitweb: https://git.kernel.org/tip/99ef9f59847cab1f9091cd4b9d7efbee0ae4fc86
Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
AuthorDate: Wed, 05 Jun 2024 10:18:56 -05:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Mon, 17 Jun 2024 20:42:58 +02:00
x86/sev: Allow non-VMPL0 execution when an SVSM is present
To allow execution at a level other than VMPL0, an SVSM must be present.
Allow the SEV-SNP guest to continue booting if an SVSM is detected and
the hypervisor supports the SVSM feature as indicated in the GHCB
hypervisor features bitmap.
[ bp: Massage a bit. ]
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/2ce7cf281cce1d0cba88f3f576687ef75dc3c953.1717600736.git.thomas.lendacky@xxxxxxx
---
arch/x86/boot/compressed/sev.c | 17 ++++++++++++++---
arch/x86/include/asm/sev-common.h | 1 +
arch/x86/kernel/sev.c | 20 ++++++++++++--------
3 files changed, 27 insertions(+), 11 deletions(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index ce941a9..6970572 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -610,11 +610,15 @@ void sev_enable(struct boot_params *bp)
* features.
*/
if (sev_status & MSR_AMD64_SEV_SNP_ENABLED) {
- if (!(get_hv_features() & GHCB_HV_FT_SNP))
+ u64 hv_features;
+ int ret;
+
+ hv_features = get_hv_features();
+ if (!(hv_features & GHCB_HV_FT_SNP))
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
/*
- * Enforce running at VMPL0.
+ * Enforce running at VMPL0 or with an SVSM.
*
* Use RMPADJUST (see the rmpadjust() function for a description of
* what the instruction does) to update the VMPL1 permissions of a
@@ -623,7 +627,14 @@ void sev_enable(struct boot_params *bp)
* only ever run at a single VMPL level so permission mask changes of a
* lesser-privileged VMPL are a don't-care.
*/
- if (rmpadjust((unsigned long)&boot_ghcb_page, RMP_PG_SIZE_4K, 1))
+ ret = rmpadjust((unsigned long)&boot_ghcb_page, RMP_PG_SIZE_4K, 1);
+
+ /*
+ * Running at VMPL0 is not required if an SVSM is present and the hypervisor
+ * supports the required SVSM GHCB events.
+ */
+ if (ret &&
+ !(snp_vmpl && (hv_features & GHCB_HV_FT_SNP_MULTI_VMPL)))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
}
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 78a4c25..e90d403 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -122,6 +122,7 @@ enum psc_op {
#define GHCB_HV_FT_SNP BIT_ULL(0)
#define GHCB_HV_FT_SNP_AP_CREATION BIT_ULL(1)
+#define GHCB_HV_FT_SNP_MULTI_VMPL BIT_ULL(5)
/*
* SNP Page State Change NAE event
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 53ac3e0..726d9df 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2352,23 +2352,27 @@ static void dump_cpuid_table(void)
* 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.
+ *
+ * If running as an SNP guest, report the current VM privilege level (VMPL).
*/
-static int __init report_cpuid_table(void)
+static int __init report_snp_info(void)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();
- if (!cpuid_table->count)
- return 0;
+ if (cpuid_table->count) {
+ pr_info("Using SNP CPUID table, %d entries present.\n",
+ cpuid_table->count);
- pr_info("Using SNP CPUID table, %d entries present.\n",
- cpuid_table->count);
+ if (sev_cfg.debug)
+ dump_cpuid_table();
+ }
- if (sev_cfg.debug)
- dump_cpuid_table();
+ if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+ pr_info("SNP running at VMPL%u.\n", snp_vmpl);
return 0;
}
-arch_initcall(report_cpuid_table);
+arch_initcall(report_snp_info);
static int __init init_sev_config(char *str)
{
|