[PATCH 5.11 102/601] KVM: SVM: Do not set sev->es_active until KVM_SEV_ES_INIT completes

Greg Kroah-Hartman
2021-05-12T17:02:21Z

From: Sean Christopherson <seanjc@google.com>

commit 9fa1521daafb58d878d03d75f6863a11312fae22 upstream.

Set sev->es_active only after the guts of KVM_SEV_ES_INIT succeeds. If
the command fails, e.g. because SEV is already active or there are no
available ASIDs, then es_active will be left set even though the VM is
not fully SEV-ES capable.

Refactor the code so that "es_active" is passed on the stack instead of
being prematurely shoved into sev_info, both to avoid having to unwind
sev_info and so that it's more obvious what actually consumes es_active
in sev_guest_init() and its helpers.

Fixes: ad73109ae7ec ("KVM: SVM: Provide support to launch and run an SEV-ES guest")
Cc: stable@vger.kernel.org
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210331031936.2495277-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/svm/sev.c | 29 ++++++++++++-----------------
1 file changed, 12 insertions(+), 17 deletions(-)

--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -86,7 +86,7 @@ static bool __sev_recycle_asids(int min_
return true;
}

-static int sev_asid_new(struct kvm_sev_info *sev)
+static int sev_asid_new(bool es_active)
{
int pos, min_asid, max_asid;
bool retry = true;
@@ -97,8 +97,8 @@ static int sev_asid_new(struct kvm_sev_i
* 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 ? 0 : min_sev_asid - 1;
- max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
+ min_asid = es_active ? 0 : min_sev_asid - 1;
+ max_asid = es_active ? min_sev_asid - 1 : max_sev_asid;
again:
pos = find_next_zero_bit(sev_asid_bitmap, max_sev_asid, min_asid);
if (pos >= max_asid) {
@@ -178,13 +178,14 @@ static void sev_unbind_asid(struct kvm *
static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ bool es_active = argp->id == KVM_SEV_ES_INIT;
int asid, ret;

ret = -EBUSY;
if (unlikely(sev->active))
return ret;

- asid = sev_asid_new(sev);
+ asid = sev_asid_new(es_active);
if (asid < 0)
return ret;

@@ -193,6 +194,7 @@ static int sev_guest_init(struct kvm *kv
goto e_free;

sev->active = true;
+ sev->es_active = es_active;
sev->asid = asid;
INIT_LIST_HEAD(&sev->regions_list);

@@ -203,16 +205,6 @@ e_free:
return ret;
}

-static int sev_es_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
-{
- if (!sev_es)
- return -ENOTTY;
-
- to_kvm_svm(kvm)->sev_info.es_active = true;
-
- return sev_guest_init(kvm, argp);
-}
-
static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
{
struct sev_data_activate *data;
@@ -1059,12 +1051,15 @@ int svm_mem_enc_op(struct kvm *kvm, void
mutex_lock(&kvm->lock);

switch (sev_cmd.id) {
+ case KVM_SEV_ES_INIT:
+ if (!sev_es) {
+ r = -ENOTTY;
+ goto out;
+ }
+ fallthrough;
case KVM_SEV_INIT:
r = sev_guest_init(kvm, &sev_cmd);
break;
- case KVM_SEV_ES_INIT:
- r = sev_es_guest_init(kvm, &sev_cmd);
- break;
case KVM_SEV_LAUNCH_START:
r = sev_launch_start(kvm, &sev_cmd);
break;