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SubjectRe: [PATCH v3 02/12] KVM: x86/mmu: bump mmu notifier count in kvm_zap_gfn_range
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On 02/08/21 20:33, Maxim Levitsky wrote:
> This together with previous patch, ensures that
> kvm_zap_gfn_range doesn't race with page fault
> running on another vcpu, and will make this page fault code
> retry instead.
>
> This is based on a patch suggested by Sean Christopherson:
> https://lkml.org/lkml/2021/7/22/1025
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 4 ++++
> include/linux/kvm_host.h | 5 +++++
> virt/kvm/kvm_main.c | 7 +++++--
> 3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 9d78cb1c0f35..9da635e383c2 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5640,6 +5640,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
>
> write_lock(&kvm->mmu_lock);
>
> + kvm_inc_notifier_count(kvm, gfn_start, gfn_end);
> +
> if (kvm_memslots_have_rmaps(kvm)) {
> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> slots = __kvm_memslots(kvm, i);
> @@ -5671,6 +5673,8 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> if (flush)
> kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);
>
> + kvm_dec_notifier_count(kvm, gfn_start, gfn_end);
> +
> write_unlock(&kvm->mmu_lock);
> }
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 9d6b4ad407b8..962e11a73e8e 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -985,6 +985,11 @@ 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);
> +
> long kvm_arch_dev_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg);
> long kvm_arch_vcpu_ioctl(struct file *filp,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index a96cbe24c688..71042cd807b3 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -608,7 +608,7 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
> kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn);
> }
>
> -static void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,
> +void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,
> unsigned long end)
> {
> /*
> @@ -636,6 +636,7 @@ static void kvm_inc_notifier_count(struct kvm *kvm, unsigned long start,
> max(kvm->mmu_notifier_range_end, end);
> }
> }
> +EXPORT_SYMBOL_GPL(kvm_inc_notifier_count);
>
> static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
> const struct mmu_notifier_range *range)
> @@ -670,7 +671,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
> return 0;
> }
>
> -static void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,
> +void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,
> unsigned long end)
> {
> /*
> @@ -687,6 +688,8 @@ static void kvm_dec_notifier_count(struct kvm *kvm, unsigned long start,
> */
> kvm->mmu_notifier_count--;
> }
> +EXPORT_SYMBOL_GPL(kvm_dec_notifier_count);
> +
>
> static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
> const struct mmu_notifier_range *range)
>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

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