Hi Gavin,
On 2021/3/15 17:56, Gavin Shan wrote:
> Hi Keqian,
>
> On 3/15/21 7:25 PM, Keqian Zhu wrote:
>> On 2021/3/15 12:18, Gavin Shan wrote:
>>> We needn't retrieve the memory slot again in user_mem_abort() because
>>> the corresponding memory slot has been passed from the caller. This
>> I think you are right, though fault_ipa will be adjusted when we try to use block mapping,
>> the fault_supports_stage2_huge_mapping() makes sure we're not trying to map anything
>> not covered by the memslot, so the adjusted fault_ipa still belongs to the memslot.
>>
>
> Yeah, it's correct. Besides, the @logging_active is determined
> based on the passed memory slot. It means user_mem_abort() can't
> support memory range which spans multiple memory slot.
>
>>> would save some CPU cycles. For example, the time used to write 1GB
>>> memory, which is backed by 2MB hugetlb pages and write-protected, is
>>> dropped by 6.8% from 928ms to 864ms.
>>>
>>> Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
>>> ---
>>> arch/arm64/kvm/mmu.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>>> index a5a8ade9fde4..4a4abcccfafb 100644
>>> --- a/arch/arm64/kvm/mmu.c
>>> +++ b/arch/arm64/kvm/mmu.c
>>> @@ -846,7 +846,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>> */
>>> smp_rmb();
>>> - pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
>>> + pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
>>> + write_fault, &writable, NULL);
>> It's better to update the code comments at same time.
>>
>
> I guess you need some comments here? If so, I would add something
> like below in v2:
>
> /*
> * gfn_to_pfn_prot() can be used either with unnecessary overhead
> * introduced to locate the memory slot because the memory slot is
> * always fixed even @gfn is adjusted for huge pages.
> */
Looks good.
See comments above "smp_rmb();", and actually my meaning is that we should change "gfn_to_pfn_prot"
to "__gfn_to_pfn_memslot" :)
Thanks,
Keqian
>
>>> if (pfn == KVM_PFN_ERR_HWPOISON) {
>>> kvm_send_hwpoison_signal(hva, vma_shift);
>>> return 0;
>>> @@ -912,7 +913,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>> /* Mark the page dirty only if the fault is handled successfully */
>>> if (writable && !ret) {
>>> kvm_set_pfn_dirty(pfn);
>>> - mark_page_dirty(kvm, gfn);
>>> + mark_page_dirty_in_slot(kvm, memslot, gfn);
>>> }
>>> out_unlock:
>>>
>
> Thanks,
> Gavin
>
>
> .
>
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