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SubjectRe: [PATCH v2 1/4] KVM: arm/arm64: Share common code in user_mem_abort()
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Christoffer Dall <christoffer.dall@arm.com> writes:

> On Tue, May 01, 2018 at 11:26:56AM +0100, Punit Agrawal wrote:
>> The code for operations such as marking the pfn as dirty, and
>> dcache/icache maintenance during stage 2 fault handling is duplicated
>> between normal pages and PMD hugepages.
>>
>> Instead of creating another copy of the operations when we introduce
>> PUD hugepages, let's share them across the different pagesizes.
>>
>> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
>> Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> virt/kvm/arm/mmu.c | 66 +++++++++++++++++++++++++++-------------------
>> 1 file changed, 39 insertions(+), 27 deletions(-)
>>
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index 7f6a944db23d..686fc6a4b866 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c

[...]

>> @@ -1517,28 +1533,34 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> if (mmu_notifier_retry(kvm, mmu_seq))
>> goto out_unlock;
>>
>> - if (!hugetlb && !force_pte)
>> + if (!hugetlb && !force_pte) {
>> hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
>> + /*
>> + * Only PMD_SIZE transparent hugepages(THP) are
>> + * currently supported. This code will need to be
>> + * updated to support other THP sizes.
>> + */
>> + if (hugetlb)
>> + vma_pagesize = PMD_SIZE;
>
> nit: this is a bit of a trap waiting to happen, as the suggested
> semantics of hugetlb is now hugetlbfs and not THP.
>
> It may be slightly nicer to do do:
>
> if (transparent_hugepage_adjust(&pfn, &fault_ipa))
> vma_pagesize = PMD_SIZE;

I should've noticed this.

I'll incorporate your suggestion and update the condition below using
hugetlb to rely on vma_pagesize instead.

Thanks,
Punit

>
>> + }
>> +
>> + if (writable)
>> + kvm_set_pfn_dirty(pfn);
>> +
>> + if (fault_status != FSC_PERM)
>> + clean_dcache_guest_page(pfn, vma_pagesize);
>> +
>> + if (exec_fault)
>> + invalidate_icache_guest_page(pfn, vma_pagesize);
>>
>> if (hugetlb) {
>> pmd_t new_pmd = pfn_pmd(pfn, mem_type);
>> new_pmd = pmd_mkhuge(new_pmd);
>> - if (writable) {
>> + if (writable)
>> new_pmd = kvm_s2pmd_mkwrite(new_pmd);
>> - kvm_set_pfn_dirty(pfn);
>> - }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PMD_SIZE);
>> -
>> - if (exec_fault) {
>> + if (stage2_should_exec(kvm, fault_ipa, exec_fault, fault_status))
>> new_pmd = kvm_s2pmd_mkexec(new_pmd);
>> - invalidate_icache_guest_page(pfn, PMD_SIZE);
>> - } else if (fault_status == FSC_PERM) {
>> - /* Preserve execute if XN was already cleared */
>> - if (stage2_is_exec(kvm, fault_ipa))
>> - new_pmd = kvm_s2pmd_mkexec(new_pmd);
>> - }
>>
>> ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
>> } else {
>> @@ -1546,21 +1568,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>
>> if (writable) {
>> new_pte = kvm_s2pte_mkwrite(new_pte);
>> - kvm_set_pfn_dirty(pfn);
>> mark_page_dirty(kvm, gfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PAGE_SIZE);
>> -
>> - if (exec_fault) {
>> + if (stage2_should_exec(kvm, fault_ipa, exec_fault, fault_status))
>> new_pte = kvm_s2pte_mkexec(new_pte);
>> - invalidate_icache_guest_page(pfn, PAGE_SIZE);
>> - } else if (fault_status == FSC_PERM) {
>> - /* Preserve execute if XN was already cleared */
>> - if (stage2_is_exec(kvm, fault_ipa))
>> - new_pte = kvm_s2pte_mkexec(new_pte);
>> - }
>>
>> ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, flags);
>> }
>> --
>> 2.17.0
>>
>
> Otherwise looks good.
>
> Thanks,
> -Christoffer
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

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