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

Sean Christopherson
2021-01-14T17:13:39Z

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")
> > Cc: Tom Lendacky <thomas.lendacky@amd.com>
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> > 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!