Re: [RFC PATCH v3 09/16] KVM: arm64: Use separate function for the mapping size in user_mem_abort()

From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Haibo Xu <haibo.xu@linaro.org>
Cc: maz@kernel.org, will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v3 09/16] KVM: arm64: Use separate function for the mapping size in user_mem_abort()
Date: Wed, 2 Dec 2020 16:29:00 +0000	[thread overview]
Message-ID: <81782b0e-cb7a-3f76-3579-ad0fddf37638@arm.com> (raw)
In-Reply-To: <CAJc+Z1F1aEU=-qiCdDD8GhS3bhFvuhgPqtqTbBHF3RZgwznHgA@mail.gmail.com>

Hi Haibo,

On 11/5/20 10:01 AM, Haibo Xu wrote:
> On Wed, 28 Oct 2020 at 01:26, Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>> user_mem_abort() is already a long and complex function, let's make it
>> slightly easier to understand by abstracting the algorithm for choosing the
>> stage 2 IPA entry size into its own function.
>>
>> This also makes it possible to reuse the code when guest SPE support will
>> be added.
>>
> Better to mention that there is "No functional change"!

That's a good point, I'll add it.

Thanks,

Alex

>
>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
>> ---
>>  arch/arm64/kvm/mmu.c | 55 ++++++++++++++++++++++++++------------------
>>  1 file changed, 33 insertions(+), 22 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 19aacc7d64de..c3c43555490d 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -738,12 +738,43 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot,
>>         return PAGE_SIZE;
>>  }
>>
>> +static short stage2_max_pageshift(struct kvm_memory_slot *memslot,
>> +                                 struct vm_area_struct *vma, hva_t hva,
>> +                                 bool *force_pte)
>> +{
>> +       short pageshift;
>> +
>> +       *force_pte = false;
>> +
>> +       if (is_vm_hugetlb_page(vma))
>> +               pageshift = huge_page_shift(hstate_vma(vma));
>> +       else
>> +               pageshift = PAGE_SHIFT;
>> +
>> +       if (memslot_is_logging(memslot) || (vma->vm_flags & VM_PFNMAP)) {
>> +               *force_pte = true;
>> +               pageshift = PAGE_SHIFT;
>> +       }
>> +
>> +       if (pageshift == PUD_SHIFT &&
>> +           !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
>> +               pageshift = PMD_SHIFT;
>> +
>> +       if (pageshift == PMD_SHIFT &&
>> +           !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
>> +               *force_pte = true;
>> +               pageshift = PAGE_SHIFT;
>> +       }
>> +
>> +       return pageshift;
>> +}
>> +
>>  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>                           struct kvm_memory_slot *memslot, unsigned long hva,
>>                           unsigned long fault_status)
>>  {
>>         int ret = 0;
>> -       bool write_fault, writable, force_pte = false;
>> +       bool write_fault, writable, force_pte;
>>         bool exec_fault;
>>         bool device = false;
>>         unsigned long mmu_seq;
>> @@ -776,27 +807,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>                 return -EFAULT;
>>         }
>>
>> -       if (is_vm_hugetlb_page(vma))
>> -               vma_shift = huge_page_shift(hstate_vma(vma));
>> -       else
>> -               vma_shift = PAGE_SHIFT;
>> -
>> -       if (logging_active ||
>> -           (vma->vm_flags & VM_PFNMAP)) {
>> -               force_pte = true;
>> -               vma_shift = PAGE_SHIFT;
>> -       }
>> -
>> -       if (vma_shift == PUD_SHIFT &&
>> -           !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE))
>> -              vma_shift = PMD_SHIFT;
>> -
>> -       if (vma_shift == PMD_SHIFT &&
>> -           !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) {
>> -               force_pte = true;
>> -               vma_shift = PAGE_SHIFT;
>> -       }
>> -
>> +       vma_shift = stage2_max_pageshift(memslot, vma, hva, &force_pte);
>>         vma_pagesize = 1UL << vma_shift;
>>         if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE)
>>                 fault_ipa &= ~(vma_pagesize - 1);
>> --
>> 2.29.1
>>
>> _______________________________________________
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>> kvmarm@lists.cs.columbia.edu
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