On 04/01/19 17:30, Sean Christopherson wrote:
>> +
>> + if (kvm_available_flush_tlb_with_range()
>> + && (tmp_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)) {
>> + struct kvm_mmu_page *leaf_sp = page_header(sp->spt[i]
>> + & PT64_BASE_ADDR_MASK);
>> + list_add(&leaf_sp->flush_link, &flush_list);
>> + }
>> +
>> + set_spte_ret |= tmp_spte_ret;
>> +
>> }
>>
>> if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)
>> - kvm_flush_remote_tlbs(vcpu->kvm);
>> + kvm_flush_remote_tlbs_with_list(vcpu->kvm, &flush_list);
> This is a bit confusing and potentially fragile. It's not obvious that
> kvm_flush_remote_tlbs_with_list() is guaranteed to call
> kvm_flush_remote_tlbs() when kvm_available_flush_tlb_with_range() is
> false, and you're relying on the kvm_flush_remote_tlbs_with_list() call
> chain to never optimize away the empty list case. Rechecking
> kvm_available_flush_tlb_with_range() isn't expensive.
>
Alternatively, do not check it during the loop: always build the
flush_list, and always call kvm_flush_remote_tlbs_with_list. The
function can then check whether the list is empty, and the OR of
tmp_spte_ret on every iteration goes away.
Paolo
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