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KVM: SVM: Add support for allowing zero SEV ASIDs

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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: 916391a2d1 ("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>
This commit is contained in:
Ashish Kalra 2024-01-31 15:56:08 -08:00 committed by Sean Christopherson
parent 466eec4a22
commit 0aa6b90ef9
1 changed files with 19 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
arch/x86/kvm/svm/sev.c
View File

@ -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) 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; bool retry = true;
int ret; int ret;
if (min_asid > max_asid)
return -ENOTTY;
WARN_ON(sev->misc_cg); WARN_ON(sev->misc_cg);
sev->misc_cg = get_current_misc_cg(); sev->misc_cg = get_current_misc_cg();
ret = sev_misc_cg_try_charge(sev); 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); 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: again:
asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid); asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
if (asid > max_asid) { if (asid > max_asid) {
@ -2234,8 +2239,10 @@ void __init sev_hardware_setup(void)
goto out; goto out;
} }
sev_asid_count = max_sev_asid - min_sev_asid + 1; if (min_sev_asid <= max_sev_asid) {
WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)); 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_supported = true;
/* SEV-ES support requested? */ /* SEV-ES support requested? */
@ -2266,7 +2273,9 @@ void __init sev_hardware_setup(void)
out: out:
if (boot_cpu_has(X86_FEATURE_SEV)) if (boot_cpu_has(X86_FEATURE_SEV))
pr_info("SEV %s (ASIDs %u - %u)\n", 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); min_sev_asid, max_sev_asid);
if (boot_cpu_has(X86_FEATURE_SEV_ES)) if (boot_cpu_has(X86_FEATURE_SEV_ES))
pr_info("SEV-ES %s (ASIDs %u - %u)\n", pr_info("SEV-ES %s (ASIDs %u - %u)\n",