On Fri, Jul 15, 2022 at 01:36:15PM +0200, Gupta, Pankaj wrote: > > Currently in mmu_notifier validate path, hva range is recorded and then > > checked in the mmu_notifier_retry_hva() from page fault path. However > > for the to be introduced private memory, a page fault may not have a hva > > As this patch appeared in v7, just wondering did you see an actual bug > because of it? And not having corresponding 'hva' occurs only with private > memory because its not mapped to host userspace? The addressed problem is not new in this version, previous versions I also had code to handle it (just in different way). But the problem is: mmu_notifier/memfile_notifier may be in the progress of invalidating a pfn that obtained earlier in the page fault handler, when happens, we should retry the fault. In v6 I used global mmu_notifier_retry() for memfile_notifier but that can block unrelated mmu_notifer invalidation which has hva range specified. Sean gave a comment at https://lkml.org/lkml/2022/6/17/1001 to separate memfile_notifier from mmu_notifier but during the implementation I realized we actually can reuse the same code for shared and private memory if both using gpa range and that can simplify the code handling in kvm_zap_gfn_range and some other code (e.g. we don't need two versions for memfile_notifier/mmu_notifier). Adding gpa range for private memory invalidation also relieves the above blocking issue between private memory page fault and mmu_notifier. Chao > > Thanks, > Pankaj > > > associated, checking gfn(gpa) makes more sense. For existing non private > > memory case, gfn is expected to continue to work. > > > > The patch also fixes a potential bug in kvm_zap_gfn_range() which has > > already been using gfn when calling kvm_inc/dec_notifier_count() in > > current code. > > > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > > --- > > arch/x86/kvm/mmu/mmu.c | 2 +- > > include/linux/kvm_host.h | 18 ++++++++---------- > > virt/kvm/kvm_main.c | 6 +++--- > > 3 files changed, 12 insertions(+), 14 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index f7fa4c31b7c5..0d882fad4bc1 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -4182,7 +4182,7 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu, > > return true; > > return fault->slot && > > - mmu_notifier_retry_hva(vcpu->kvm, mmu_seq, fault->hva); > > + mmu_notifier_retry_gfn(vcpu->kvm, mmu_seq, fault->gfn); > > } > > static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 0bdb6044e316..e9153b54e2a4 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -767,8 +767,8 @@ struct kvm { > > 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; > > + gfn_t mmu_notifier_range_start; > > + gfn_t mmu_notifier_range_end; > > #endif > > struct list_head devices; > > u64 manual_dirty_log_protect; > > @@ -1362,10 +1362,8 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc); > > void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc); > > #endif > > -void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > -void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > +void kvm_inc_notifier_count(struct kvm *kvm, gfn_t start, gfn_t end); > > +void kvm_dec_notifier_count(struct kvm *kvm, gfn_t start, gfn_t end); > > long kvm_arch_dev_ioctl(struct file *filp, > > unsigned int ioctl, unsigned long arg); > > @@ -1923,9 +1921,9 @@ static inline int mmu_notifier_retry(struct kvm *kvm, unsigned long mmu_seq) > > return 0; > > } > > -static inline int mmu_notifier_retry_hva(struct kvm *kvm, > > +static inline int mmu_notifier_retry_gfn(struct kvm *kvm, > > unsigned long mmu_seq, > > - unsigned long hva) > > + gfn_t gfn) > > { > > lockdep_assert_held(&kvm->mmu_lock); > > /* > > @@ -1935,8 +1933,8 @@ static inline int mmu_notifier_retry_hva(struct kvm *kvm, > > * positives, due to shortcuts when handing concurrent invalidations. > > */ > > if (unlikely(kvm->mmu_notifier_count) && > > - hva >= kvm->mmu_notifier_range_start && > > - hva < kvm->mmu_notifier_range_end) > > + gfn >= kvm->mmu_notifier_range_start && > > + gfn < kvm->mmu_notifier_range_end) > > return 1; > > if (kvm->mmu_notifier_seq != mmu_seq) > > return 1; > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index da263c370d00..4d7f0e72366f 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -536,8 +536,7 @@ static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn, > > typedef bool (*hva_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range); > > -typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > +typedef void (*on_lock_fn_t)(struct kvm *kvm, gfn_t start, gfn_t end); > > typedef void (*on_unlock_fn_t)(struct kvm *kvm); > > @@ -624,7 +623,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, > > locked = true; > > KVM_MMU_LOCK(kvm); > > if (!IS_KVM_NULL_FN(range->on_lock)) > > - range->on_lock(kvm, range->start, range->end); > > + range->on_lock(kvm, gfn_range.start, > > + gfn_range.end); > > if (IS_KVM_NULL_FN(range->handler)) > > break; > > }
