On Wed, Jul 19, 2023, Vishal Annapurve wrote:
> On Tue, Jul 18, 2023 at 4:49 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > ...
> > +static int kvm_gmem_error_page(struct address_space *mapping, struct page *page)
> > +{
> > + struct list_head *gmem_list = &mapping->private_list;
> > + struct kvm_memory_slot *slot;
> > + struct kvm_gmem *gmem;
> > + unsigned long index;
> > + pgoff_t start, end;
> > + gfn_t gfn;
> > +
> > + filemap_invalidate_lock_shared(mapping);
> > +
> > + start = page->index;
> > + end = start + thp_nr_pages(page);
> > +
> > + list_for_each_entry(gmem, gmem_list, entry) {
> > + xa_for_each_range(&gmem->bindings, index, slot, start, end - 1) {
> > + for (gfn = start; gfn < end; gfn++) {
> > + if (WARN_ON_ONCE(gfn < slot->base_gfn ||
> > + gfn >= slot->base_gfn + slot->npages))
> > + continue;
> > +
> > + /*
> > + * FIXME: Tell userspace that the *private*
> > + * memory encountered an error.
> > + */
> > + send_sig_mceerr(BUS_MCEERR_AR,
> > + (void __user *)gfn_to_hva_memslot(slot, gfn),
> > + PAGE_SHIFT, current);
>
> Does it make sense to replicate what happens with MCE handling on
> tmpfs backed guest memory:
> 1) Unmap gpa from guest
> 2) On the next guest EPT fault, exit to userspace to handle/log the
> mce error for the gpa.
Hmm, yes, that would be much better. Ah, and kvm_gmem_get_pfn() needs to check
folio_test_hwpoison() and potentially PageHWPoison(). E.g. if the folio is huge,
KVM needs to restrict the mapping to order-0 (target page isn't poisoned), or
return KVM_PFN_ERR_HWPOISON (taget page IS poisoned).
Alternatively, KVM could punch a hole in kvm_gmem_error_page(), but I don't think
we want to do that because that would prevent forwarding the #MC to the guest.
