On Tue, Mar 29, 2022 at 07:23:04PM +0000, Sean Christopherson wrote:
> On Thu, Mar 10, 2022, Chao Peng wrote:
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 67349421eae3..52319f49d58a 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -841,8 +841,43 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
> > #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
> >
> > #ifdef CONFIG_MEMFILE_NOTIFIER
> > +static void kvm_memfile_notifier_handler(struct memfile_notifier *notifier,
> > + pgoff_t start, pgoff_t end)
> > +{
> > + int idx;
> > + struct kvm_memory_slot *slot = container_of(notifier,
> > + struct kvm_memory_slot,
> > + notifier);
> > + struct kvm_gfn_range gfn_range = {
> > + .slot = slot,
> > + .start = start - (slot->private_offset >> PAGE_SHIFT),
> > + .end = end - (slot->private_offset >> PAGE_SHIFT),
> > + .may_block = true,
> > + };
> > + struct kvm *kvm = slot->kvm;
> > +
> > + gfn_range.start = max(gfn_range.start, slot->base_gfn);
> > + gfn_range.end = min(gfn_range.end, slot->base_gfn + slot->npages);
> > +
> > + if (gfn_range.start >= gfn_range.end)
> > + return;
> > +
> > + idx = srcu_read_lock(&kvm->srcu);
> > + KVM_MMU_LOCK(kvm);
> > + kvm_unmap_gfn_range(kvm, &gfn_range);
> > + kvm_flush_remote_tlbs(kvm);
>
> This should check the result of kvm_unmap_gfn_range() and flush only if necessary.
Yep.
>
> kvm->mmu_notifier_seq needs to be incremented, otherwise KVM will incorrectly
> install a SPTE if the mapping is zapped between retrieving the pfn in faultin and
> installing it after acquire mmu_lock.
Good catch.
Chao
>
>
> > + KVM_MMU_UNLOCK(kvm);
> > + srcu_read_unlock(&kvm->srcu, idx);
> > +}
> > +
> > +static struct memfile_notifier_ops kvm_memfile_notifier_ops = {
> > + .invalidate = kvm_memfile_notifier_handler,
> > + .fallocate = kvm_memfile_notifier_handler,
> > +};
> > +
> > static inline int kvm_memfile_register(struct kvm_memory_slot *slot)
> > {
> > + slot->notifier.ops = &kvm_memfile_notifier_ops;
> > return memfile_register_notifier(file_inode(slot->private_file),
> > &slot->notifier,
> > &slot->pfn_ops);
> > @@ -1963,6 +1998,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
> > new->private_file = file;
> > new->private_offset = mem->flags & KVM_MEM_PRIVATE ?
> > region_ext->private_offset : 0;
> > + new->kvm = kvm;
> >
> > r = kvm_set_memslot(kvm, old, new, change);
> > if (!r)
> > --
> > 2.17.1
> >
