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.
Thanks,
Paolo
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