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KVM: SVM: Move lock-protected allocation of SEV ASID into a separate helper

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Extract the lock-protected parts of SEV ASID allocation into a new helper
and opportunistically convert it to use guard() when acquiring the mutex.

Preserve the goto even though it's a little odd, as it's there's a fair
amount of subtlety that makes it surprisingly difficult to replicate the
functionality with a loop construct, and arguably using goto yields the
most readable code.

No functional change intended.

Signed-off-by: Carlos López <clopez@suse.de>
[sean: move code to separate helper, rework shortlog+changelog]
Link: https://patch.msgid.link/20260310234829.2608037-21-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Carlos López
2026-03-10 16:48:28 -07:00
committed by Sean Christopherson
parent f09b7f4af9
commit 1d353dae3d
1 changed files with 23 additions and 14 deletions
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37
arch/x86/kvm/svm/sev.c
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@@ -237,6 +237,28 @@ static void sev_misc_cg_uncharge(struct kvm_sev_info *sev)
misc_cg_uncharge(type, sev->misc_cg, 1);
}
static unsigned int sev_alloc_asid(unsigned int min_asid, unsigned int max_asid)
{
unsigned int asid;
bool retry = true;
guard(mutex)(&sev_bitmap_lock);
again:
asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
if (asid > max_asid) {
if (retry && __sev_recycle_asids(min_asid, max_asid)) {
retry = false;
goto again;
}
return asid;
}
__set_bit(asid, sev_asid_bitmap);
return asid;
}
static int sev_asid_new(struct kvm_sev_info *sev, unsigned long vm_type)
{
/*
@@ -244,7 +266,6 @@ static int sev_asid_new(struct kvm_sev_info *sev, unsigned long vm_type)
* SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
*/
unsigned int min_asid, max_asid, asid;
bool retry = true;
int ret;
if (vm_type == KVM_X86_SNP_VM) {
@@ -277,24 +298,12 @@ static int sev_asid_new(struct kvm_sev_info *sev, unsigned long vm_type)
return ret;
}
mutex_lock(&sev_bitmap_lock);
again:
asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid);
asid = sev_alloc_asid(min_asid, max_asid);
if (asid > max_asid) {
if (retry && __sev_recycle_asids(min_asid, max_asid)) {
retry = false;
goto again;
}
mutex_unlock(&sev_bitmap_lock);
ret = -EBUSY;
goto e_uncharge;
}
__set_bit(asid, sev_asid_bitmap);
mutex_unlock(&sev_bitmap_lock);
sev->asid = asid;
return 0;
e_uncharge: