From: Ashish Kalra ashish.kalra@amd.com
Some BIOSes allow the end user to set the minimum SEV ASID value (CPUID 0x8000001F_EDX) to be greater than the maximum number of encrypted guests, or maximum SEV ASID value (CPUID 0x8000001F_ECX) in order to dedicate all the SEV ASIDs to SEV-ES or SEV-SNP.
The SEV support, as coded, does not handle the case where the minimum SEV ASID value can be greater than the maximum SEV ASID value. As a result, the following confusing message is issued:
[ 30.715724] kvm_amd: SEV enabled (ASIDs 1007 - 1006)
Fix the support to properly handle this case.
Fixes: 916391a2d1dc ("KVM: SVM: Add support for SEV-ES capability in KVM") Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Ashish Kalra ashish.kalra@amd.com Cc: stable@vger.kernel.org Acked-by: Tom Lendacky thomas.lendacky@amd.com Link: https://lore.kernel.org/r/20240104190520.62510-1-Ashish.Kalra@amd.com Link: https://lore.kernel.org/r/20240131235609.4161407-4-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com --- arch/x86/kvm/svm/sev.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index eeef43c795d8..5f8312edee36 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -144,10 +144,21 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev)
static int sev_asid_new(struct kvm_sev_info *sev) { - unsigned int asid, min_asid, max_asid; + /* + * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid. + * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1. + * Note: min ASID can end up larger than the max if basic SEV support is + * effectively disabled by disallowing use of ASIDs for SEV guests. + */ + unsigned int min_asid = sev->es_active ? 1 : min_sev_asid; + unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid; + unsigned int asid; bool retry = true; int ret;
+ if (min_asid > max_asid) + return -ENOTTY; + WARN_ON(sev->misc_cg); sev->misc_cg = get_current_misc_cg(); ret = sev_misc_cg_try_charge(sev); @@ -159,12 +170,6 @@ static int sev_asid_new(struct kvm_sev_info *sev)
mutex_lock(&sev_bitmap_lock);
- /* - * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid. - * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1. - */ - min_asid = sev->es_active ? 1 : min_sev_asid; - max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid; again: asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid); if (asid > max_asid) { @@ -2234,8 +2239,10 @@ void __init sev_hardware_setup(void) goto out; }
- sev_asid_count = max_sev_asid - min_sev_asid + 1; - WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)); + if (min_sev_asid <= max_sev_asid) { + sev_asid_count = max_sev_asid - min_sev_asid + 1; + WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)); + } sev_supported = true;
/* SEV-ES support requested? */ @@ -2266,7 +2273,9 @@ void __init sev_hardware_setup(void) out: if (boot_cpu_has(X86_FEATURE_SEV)) pr_info("SEV %s (ASIDs %u - %u)\n", - sev_supported ? "enabled" : "disabled", + sev_supported ? min_sev_asid <= max_sev_asid ? "enabled" : + "unusable" : + "disabled", min_sev_asid, max_sev_asid); if (boot_cpu_has(X86_FEATURE_SEV_ES)) pr_info("SEV-ES %s (ASIDs %u - %u)\n",