Re: [PATCH 5.4] KVM: SVM: Call SEV Guest Decommission if ASID binding fails

From: Greg KH <greg@kroah.com>
To: Alper Gun <alpergun@google.com>
Cc: stable@vger.kernel.org, Peter Gonda <pgonda@google.com>,
	Marc Orr <marcorr@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 5.4] KVM: SVM: Call SEV Guest Decommission if ASID binding fails
Date: Thu, 8 Jul 2021 20:26:11 +0200	[thread overview]
Message-ID: <YOdDQwf/qY21W5uR@kroah.com> (raw)
In-Reply-To: <20210628211054.61528-1-alpergun@google.com>

On Mon, Jun 28, 2021 at 09:10:54PM +0000, Alper Gun wrote:
> 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(-)

Now queued up, thanks.

greg k-h