Hi Gavin,
On 2021/4/21 14:38, Gavin Shan wrote:
> Hi Keqian,
>
> On 4/16/21 12:03 AM, Keqian Zhu wrote:
>> The MMIO regions may be unmapped for many reasons and can be remapped
>> by stage2 fault path. Map MMIO regions at creation time becomes a
>> minor optimization and makes these two mapping path hard to sync.
>>
>> Remove the mapping code while keep the useful sanity check.
>>
>> Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
>> ---
>> arch/arm64/kvm/mmu.c | 38 +++-----------------------------------
>> 1 file changed, 3 insertions(+), 35 deletions(-)
>>
>
> After removing the logic to create stage2 mapping for VM_PFNMAP region,
> I think the "do { } while" loop becomes unnecessary and can be dropped
> completely. It means the only sanity check is to see if the memory slot
> overflows IPA space or not. In that case, KVM_MR_FLAGS_ONLY can be
> ignored because the memory slot's base address and length aren't changed
> when we have KVM_MR_FLAGS_ONLY.
Maybe not exactly. Here we do an important sanity check that we shouldn't
log dirty for memslots with VM_PFNMAP.
>
> It seems the patch isn't based on "next" branch because find_vma() was
> replaced by find_vma_intersection() by one of my patches :)
Yep, I remember it. I will replace it at next merge window...
Thanks,
Keqian
>
> Thanks,
> Gavin
>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 8711894db8c2..c59af5ca01b0 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -1301,7 +1301,6 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>> {
>> hva_t hva = mem->userspace_addr;
>> hva_t reg_end = hva + mem->memory_size;
>> - bool writable = !(mem->flags & KVM_MEM_READONLY);
>> int ret = 0;
>> if (change != KVM_MR_CREATE && change != KVM_MR_MOVE &&
>> @@ -1318,8 +1317,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>> mmap_read_lock(current->mm);
>> /*
>> * A memory region could potentially cover multiple VMAs, and any holes
>> - * between them, so iterate over all of them to find out if we can map
>> - * any of them right now.
>> + * between them, so iterate over all of them.
>> *
>> * +--------------------------------------------+
>> * +---------------+----------------+ +----------------+
>> @@ -1330,50 +1328,20 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>> */
>> do {
>> struct vm_area_struct *vma = find_vma(current->mm, hva);
>> - hva_t vm_start, vm_end;
>> if (!vma || vma->vm_start >= reg_end)
>> break;
>> - /*
>> - * Take the intersection of this VMA with the memory region
>> - */
>> - vm_start = max(hva, vma->vm_start);
>> - vm_end = min(reg_end, vma->vm_end);
>> -
>> if (vma->vm_flags & VM_PFNMAP) {
>> - gpa_t gpa = mem->guest_phys_addr +
>> - (vm_start - mem->userspace_addr);
>> - phys_addr_t pa;
>> -
>> - pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
>> - pa += vm_start - vma->vm_start;
>> -
>> /* IO region dirty page logging not allowed */
>> if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
>> ret = -EINVAL;
>> - goto out;
>> - }
>> -
>> - ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
>> - vm_end - vm_start,
>> - writable);
>> - if (ret)
>> break;
>> + }
>> }
>> - hva = vm_end;
>> + hva = min(reg_end, vma->vm_end);
>> } while (hva < reg_end);
>> - if (change == KVM_MR_FLAGS_ONLY)
>> - goto out;
>> -
>> - spin_lock(&kvm->mmu_lock);
>> - if (ret)
>> - unmap_stage2_range(&kvm->arch.mmu, mem->guest_phys_addr, mem->memory_size);
>> - else if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
>> - stage2_flush_memslot(kvm, memslot);
>> - spin_unlock(&kvm->mmu_lock);
>> -out:
>> mmap_read_unlock(current->mm);
>> return ret;
>> }
>>
>
> .
>
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