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KVM: SVM: Call SEV Guest Decommission if ASID binding fails

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Send SEV_CMD_DECOMMISSION command to PSP firmware if ASID binding
fails. If a failure happens after  a successful LAUNCH_START command,
a decommission command should be executed. Otherwise, guest context
will be unfreed inside the AMD SP. After the firmware will not have
memory to allocate more SEV guest context, LAUNCH_START command will
begin to fail with SEV_RET_RESOURCE_LIMIT error.

The existing code calls decommission inside sev_unbind_asid, but it is
not called if a failure happens before guest activation succeeds. If
sev_bind_asid fails, decommission is never called. PSP firmware has a
limit for the number of guests. If sev_asid_binding fails many times,
PSP firmware will not have resources to create another guest context.

Cc: stable@vger.kernel.org
Fixes: 59414c9892 ("KVM: SVM: Add support for KVM_SEV_LAUNCH_START command")
Reported-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Alper Gun <alpergun@google.com>
Reviewed-by: Marc Orr <marcorr@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210610174604.2554090-1-alpergun@google.com>
This commit is contained in:
Alper Gun 2021-06-10 17:46:04 +00:00 committed by Paolo Bonzini
parent 78fcb2c91a
commit 934002cd66
1 changed files with 15 additions and 5 deletions
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20
arch/x86/kvm/svm/sev.c
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@ -199,9 +199,19 @@ static void sev_asid_free(struct kvm_sev_info *sev)
sev->misc_cg = NULL;
}
static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
static void sev_decommission(unsigned int handle)
{
struct sev_data_decommission decommission;
if (!handle)
return;
decommission.handle = handle;
sev_guest_decommission(&decommission, NULL);
}
static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
{
struct sev_data_deactivate deactivate;
if (!handle)
@ -214,9 +224,7 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
sev_guest_deactivate(&deactivate, NULL);
up_read(&sev_deactivate_lock);
/* decommission handle */
decommission.handle = handle;
sev_guest_decommission(&decommission, NULL);
sev_decommission(handle);
}
static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
@ -341,8 +349,10 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
/* Bind ASID to this guest */
ret = sev_bind_asid(kvm, start.handle, error);
if (ret)
if (ret) {
sev_decommission(start.handle);
goto e_free_session;
}
/* return handle to userspace */
params.handle = start.handle;