On Thu, Sep 1, 2022 at 8:29 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Mon, Aug 29, 2022, Kyle Huey wrote:
> > @@ -1246,6 +1246,21 @@ static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf,
> > }
> > }
> >
> > + /*
> > + * Update the user protection key storage. Allow KVM to
> > + * pass in a NULL pkru pointer if the mask bit is unset
> > + * for its legacy ABI behavior.
> > + */
> > + if (pkru)
> > + *pkru = 0;
> > +
> > + if (hdr.xfeatures & XFEATURE_MASK_PKRU) {
> > + struct pkru_state *xpkru;
> > +
> > + xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU);
> > + *pkru = xpkru->pkru;
> > + }
>
> What about writing this as:
>
> if (hdr.xfeatures & XFEATURE_MASK_PKRU) {
> ...
>
> *pkru = xpkru->pkru;
> } else if (pkru) {
> *pkru = 0;
> }
>
> to make it slightly more obvious that @pkru must be non-NULL if the feature flag
> is enabled?
tglx didn't seem to like the branchiness before but maybe he'll change
his mind since we have to have the `if (pkru)` now anyways.
> Or we could be paranoid, though I'm not sure this is worthwhile.
>
> if ((hdr.xfeatures & XFEATURE_MASK_PKRU) &&
> !WARN_ON_ONCE(!pkru)) {
> ...
>
> *pkru = xpkru->pkru;
> } else if (pkru) {
> *pkru = 0;
> }
I don't feel strongly about this.
> Otherwise, looks good from a KVM perspective. Thanks!
Great.
- Kyle
