On Thu, May 19, 2022 at 11:37:12PM +0800, Chao Peng wrote: > Register private memslot to fd-based memory backing store and handle the > memfile notifiers to zap the existing mappings. > > Currently the register is happened at memslot creating time and the > initial support does not include page migration/swap. > > KVM_MEM_PRIVATE is not exposed by default, architecture code can turn > on it by implementing kvm_arch_private_mem_supported(). > > A 'kvm' reference is added in memslot structure since in > memfile_notifier callbacks we can only obtain a memslot reference while > kvm is need to do the zapping. The zapping itself reuses code from > existing mmu notifier handling. > > Co-developed-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > --- > include/linux/kvm_host.h | 10 ++- > virt/kvm/kvm_main.c | 132 ++++++++++++++++++++++++++++++++++++--- > 2 files changed, 131 insertions(+), 11 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index b0a7910505ed..00efb4b96bc7 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -246,7 +246,7 @@ 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; > @@ -577,6 +577,7 @@ struct kvm_memory_slot { > struct file *private_file; > loff_t private_offset; > struct memfile_notifier notifier; > + struct kvm *kvm; > }; > > static inline bool kvm_slot_is_private(const struct kvm_memory_slot *slot) > @@ -769,9 +770,13 @@ struct kvm { > struct hlist_head irq_ack_notifier_list; > #endif > > +#if (defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)) ||\ > + defined(CONFIG_MEMFILE_NOTIFIER) > + unsigned long mmu_notifier_seq; > +#endif > + > #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) > struct mmu_notifier mmu_notifier; > - unsigned long mmu_notifier_seq; > long mmu_notifier_count; > unsigned long mmu_notifier_range_start; > unsigned long mmu_notifier_range_end; > @@ -1438,6 +1443,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu); > int kvm_arch_post_init_vm(struct kvm *kvm); > void kvm_arch_pre_destroy_vm(struct kvm *kvm); > int kvm_arch_create_vm_debugfs(struct kvm *kvm); > +bool kvm_arch_private_mem_supported(struct kvm *kvm); > > #ifndef __KVM_HAVE_ARCH_VM_ALLOC > /* > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index db9d39a2d3a6..f93ac7cdfb53 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -843,6 +843,73 @@ static int kvm_init_mmu_notifier(struct kvm *kvm) > > #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */ > > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > +static void kvm_private_mem_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), This code assumes that 'end' is greater than slot->private_offset, but even if slot->private_offset is non-zero, nothing stops userspace from allocating pages in the range of 0 through slot->private_offset, which will still end up triggering this notifier. In that case gfn_range.end will end up going negative, and the below code will limit that to slot->npages and do a populate/invalidate for the entire range. Not sure if this covers all the cases, but this fixes the issue for me: diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 903ffdb5f01c..4c744d8f7527 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -872,6 +872,19 @@ static void kvm_private_mem_notifier_handler(struct memfile_notifier *notifier, .may_block = true, }; struct kvm *kvm = slot->kvm; + + if (slot->private_offset > end) + return; +