Hi Paolo:
Thanks for review.
On 7/18/2018 8:01 PM, Paolo Bonzini wrote:
> On 09/07/2018 11:02, Tianyu Lan wrote:
>> + /*
>> + * Call kvm_arch_hv_tlb_remote first and go back old way when
>> + * return failure.
>> + */
>> + if (!kvm_arch_hv_flush_remote_tlb(kvm))
>> + return;
>> +
>> /*
>> * Read tlbs_dirty before setting KVM_REQ_TLB_FLUSH in
>> * kvm_make_all_cpus_request.
>> */
>> - long dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
>> + dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
>
> Also, the call to kvm_arch_flush_remote_tlbs should not replace the
> whole function. It should be something like:
>
> long dirty_count = smp_load_acquire(&kvm->tlbs_dirty);
>
> /*
> * We want to publish modifications to the page tables before reading
> * mode. Pairs with a memory barrier in arch-specific code.
> * - x86: smp_mb__after_srcu_read_unlock in vcpu_enter_guest
> * and smp_mb in walk_shadow_page_lockless_begin/end.
> * - powerpc: smp_mb in kvmppc_prepare_to_enter.
> *
> * There is already an smp_mb__after_atomic() before
> * kvm_make_all_cpus_request() reads vcpu->mode. We reuse that
> * barrier here.
> */
> if (!kvm_arch_hv_flush_remote_tlb(kvm) ||
> kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
> ++kvm->stat.remote_tlb_flush;
> cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
>
> Otherwise, kvm_mmu_notifier_invalidate_range_start will incorrectly skip
> a TLB flush.
Nice catch. Will update in the next version.
>
> Thanks,
>
> Paolo
>
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