Messages in this thread Patch in this message | | | Subject | Re: [PATCH 4/4] KVM: arm64: Don't retrieve memory slot again in page fault handler | From | Gavin Shan <> | Date | Mon, 15 Mar 2021 20:56:17 +1100 |
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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@redhat.com> >> --- >> 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. */
>> 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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