Re: [PATCH v2 02/14] KVM: SVM: Free sev_asid_bitmap during init if SEV setup fails

Sean Christopherson
2021-01-14T19:18:17Z

On Thu, Jan 14, 2021, Tom Lendacky wrote:
> On 1/14/21 11:12 AM, Sean Christopherson wrote:
> > On Thu, Jan 14, 2021, Tom Lendacky wrote:
> > > On 1/13/21 6:36 PM, Sean Christopherson wrote:
> > > > Free sev_asid_bitmap if the reclaim bitmap allocation fails, othwerise
> > > > KVM will unnecessarily keep the bitmap when SEV is not fully enabled.
> > > >
> > > > Freeing the page is also necessary to avoid introducing a bug when a
> > > > future patch eliminates svm_sev_enabled() in favor of using the global
> > > > 'sev' flag directly. While sev_hardware_enabled() checks max_sev_asid,
> > > > which is true even if KVM setup fails, 'sev' will be true if and only
> > > > if KVM setup fully succeeds.
> > > >
> > > > Fixes: 33af3a7ef9e6 ("KVM: SVM: Reduce WBINVD/DF_FLUSH invocations")
>
> Oops, missed this last time... I don't think the Fixes: tag is needed
> anymore unless you don't want the memory consumption of the first bitmap,

If Fixes is viewed as purely a "this needs to be backported", then yes, it
should be dropped. But, since KVM policy is to backport only patches that are
explicitly tagged with stable@, I like to use to Fixes to create a paper trail
for bug fixes even if the bug is essentially benign.

That being said, I have no objection to dropping it if anyone feels strongly
about not playing fast and loose with Fixes.

> should the allocation of the second bitmap fail, until kvm_amd is rmmod'ed.
> Up to you.