On 2018-12-13 12:59:07 [-0500], Steven Rostedt wrote:
> On Thu, 13 Dec 2018 17:44:31 +0100
> Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
>
> > Disable preemption to avoid the warning in __flush_tlb_all().
>
> I'm guessing the reason for the warn on is that we don't want a task to
> be scheduled in where we expected the TLB to have been flushed.
during the cr3 read + write, correct.
> > --- a/arch/x86/mm/pageattr.c
> > +++ b/arch/x86/mm/pageattr.c
> > @@ -687,6 +687,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
> > pgprot_t ref_prot;
> >
> > spin_lock(&pgd_lock);
>
> We probably should have comment explaining why we have a
> preempt_disable here.
okay.
> > + preempt_disable();
> > /*
> > * Check for races, another CPU might have split this page
> > * up for us already:
> > @@ -694,6 +695,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
> > tmp = _lookup_address_cpa(cpa, address, &level);
> > if (tmp != kpte) {
> > spin_unlock(&pgd_lock);
> > + preempt_enable();
>
> Shouldn't the preempt_enable() be before the unlock?
Yeah, I noticed it once I saw the patch on the list. Will flip it before
I apply it.
> > return 1;
> > }
> >
Sebastian
