On Tue, Apr 19, 2022 at 03:43:56PM -0700, Vishal Annapurve wrote: > On Thu, Mar 10, 2022 at 6:11 AM Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > > > KVM gets notified when memory pages changed in the memory backing store. > > When userspace allocates the memory with fallocate() or frees memory > > with fallocate(FALLOC_FL_PUNCH_HOLE), memory backing store calls into > > KVM fallocate/invalidate callbacks respectively. To ensure KVM never > > maps both the private and shared variants of a GPA into the guest, in > > the fallocate callback, we should zap the existing shared mapping and > > in the invalidate callback we should zap the existing private mapping. > > > > In the callbacks, KVM firstly converts the offset range into the > > gfn_range and then calls existing kvm_unmap_gfn_range() which will zap > > the shared or private mapping. Both callbacks pass in a memslot > > reference but we need 'kvm' so add a reference in memslot structure. > > > > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > > --- > > include/linux/kvm_host.h | 3 ++- > > virt/kvm/kvm_main.c | 36 ++++++++++++++++++++++++++++++++++++ > > 2 files changed, 38 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 9b175aeca63f..186b9b981a65 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -236,7 +236,7 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > > int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu); > > #endif > > > > -#ifdef KVM_ARCH_WANT_MMU_NOTIFIER > > +#if defined(KVM_ARCH_WANT_MMU_NOTIFIER) || defined(CONFIG_MEMFILE_NOTIFIER) > > struct kvm_gfn_range { > > struct kvm_memory_slot *slot; > > gfn_t start; > > @@ -568,6 +568,7 @@ struct kvm_memory_slot { > > loff_t private_offset; > > struct memfile_pfn_ops *pfn_ops; > > struct memfile_notifier notifier; > > + struct kvm *kvm; > > }; > > > > static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot) > > 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.start seems to be page offset within the file. Should this rather be: > gfn_range.start = slot->base_gfn + min(gfn_range.start, slot->npages); Right. For start we don't really need care about the uppper bound here (will check below), so this should be enough: gfn_range.start = slot->base_gfn + gfn_range.start; > > > + gfn_range.end = min(gfn_range.end, slot->base_gfn + slot->npages); > > + > > Similar to previous comment, should this rather be: > gfn_range.end = slot->base_gfn + min(gfn_range.end, slot->npages); This is correct. Thanks, Chao > > > + 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); > > + 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 > >