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

[Greg KH <gregkh@linuxfoundation.org>]

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>

Message-id?  Odd...

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

<snip>

Can you also provide working backports for the newer kernel trees as
well?  We would need this in 5.10 and 5.12, right?

thanks,

greg k-h