commit 934002cd660b035b926438244b4294e647507e13 upstream.

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: 59414c989220 ("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 --- arch/x86/kvm/svm.c | 32 +++++++++++++++++++++----------- 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index ad24e6777277..ae94ec036137 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1791,9 +1791,25 @@ static void sev_asid_free(struct kvm *kvm) __sev_asid_free(sev->asid); }

-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 = kzalloc(sizeof(*decommission), GFP_KERNEL); + if (!decommission) + return; + + decommission->handle = handle; + sev_guest_decommission(decommission, NULL); + + kfree(decommission); +} + +static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) +{ struct sev_data_deactivate *data;

if (!handle) @@ -1811,15 +1827,7 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) sev_guest_df_flush(NULL); kfree(data);

- decommission = kzalloc(sizeof(*decommission), GFP_KERNEL); - if (!decommission) - return; - - /* decommission handle */ - decommission->handle = handle; - sev_guest_decommission(decommission, NULL); - - kfree(decommission); + sev_decommission(handle); }

static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr, @@ -6468,8 +6476,10 @@ 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;