Hi Qian,
On Thu, Jun 25, 2020 at 11:37:20AM -0400, Qian Cai wrote:
> On Thu, Jun 25, 2020 at 04:52:27PM +0200, Joerg Roedel wrote:
> > - u64 pt_root = atomic64_read(&domain->pt_root);
> > + unsigned long pt_root = domain->pt_root;
>
> The pt_root might be reload later in case of register pressure where the
> compiler decides to not store it as a stack variable, so it needs
> smp_rmb() here to match to the smp_wmb() in
> amd_iommu_domain_set_pt_root() to make the load visiable to all CPUs.
>
> Then, smp_rmb/wmb() wouldn't be able to deal with data races, so it
> needs,
>
> unsigned long pt_root = READ_ONCE(domain->pt_root);
>
> >
> > pgtable->root = (u64 *)(pt_root & PAGE_MASK);
> > pgtable->mode = pt_root & 7; /* lowest 3 bits encode pgtable mode */
> > @@ -164,7 +164,13 @@ static void amd_iommu_domain_get_pgtable(struct
> > protection_domain *domain,
> >
> > static void amd_iommu_domain_set_pt_root(struct protection_domain *domain,
> > u64 root)
> > {
> > - atomic64_set(&domain->pt_root, root);
> > + domain->pt_root = root;
>
> WRITE_ONCE(domain->pt_root, root);
Thanks for your review. I addressed your comments and will send an
updated version shortly.
Regards,
Joerg
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