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

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jul 05, 2021 at 01:40:39PM +0200, Paolo Bonzini wrote:
> On 05/07/21 09:15, Greg KH wrote:
> > 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...
> 
> Not that much, see "git log -- drivers | grep Message-Id".  A link to
> lore.kernel.org is getting more popular these days, but Message-Id is what
> "git am" knows about.
> 
> > > ---
> > >   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?
> 
> Already queued:
> 
> https://lore.kernel.org/stable/20210628141828.31757-102-sashal@kernel.org/
> for 5.12
> https://lore.kernel.org/stable/20210628142607.32218-94-sashal@kernel.org/
> for 5.10

Ah, you are right, I forgot to update my local tree, my fault.

greg k-h