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); > + 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); > + 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 >