From: Ashish Kalra <ashish.kalra@xxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Link: https://lore.kernel.org/r/20240104190520.62510-1-Ashish.Kalra@xxxxxxx
Link: https://lore.kernel.org/r/20240131235609.4161407-4-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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",
--
2.43.0
