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

[Tom Lendacky]

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

Thanks,
Tom

> > > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > > ---
> > >    arch/x86/kvm/svm/sev.c | 4 +++-
> > >    1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > > index c8ffdbc81709..0eeb6e1b803d 100644
> > > --- a/arch/x86/kvm/svm/sev.c
> > > +++ b/arch/x86/kvm/svm/sev.c
> > > @@ -1274,8 +1274,10 @@ void __init sev_hardware_setup(void)
> > >    		goto out;
> > >    	sev_reclaim_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);
> > > -	if (!sev_reclaim_asid_bitmap)
> > > +	if (!sev_reclaim_asid_bitmap) {
> > > +		bitmap_free(sev_asid_bitmap);
> >
> > Until that future change, you probably need to do sev_asid_bitmap = NULL
> > here to avoid an issue in sev_hardware_teardown() when it tries to free it
> > again.
>
> Argh, you're right.  Thanks!