On Wed, Dec 16, 2020 at 08:28:44PM +0800, Yanan Wang wrote:
> We now mark the page dirty and set the bitmap before calling fault handlers
> in user_mem_abort(), and we might end up having spurious dirty pages if
> update of permissions or mapping has failed.
> So, mark the page dirty only if the fault is handled successfully.
>
> Let the guest directly enter again but not return to userspace if we were
> trying to recreate the same mapping or only change access permissions
> with BBM, which is not permitted in the mapping path.
>
> Signed-off-by: Yanan Wang <[email protected]>
> ---
> arch/arm64/kvm/mmu.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 75814a02d189..72e516a10914 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,11 +879,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (vma_pagesize == PAGE_SIZE && !force_pte)
> vma_pagesize = transparent_hugepage_adjust(memslot, hva,
> &pfn, &fault_ipa);
> - if (writable) {
> + if (writable)
> prot |= KVM_PGTABLE_PROT_W;
> - kvm_set_pfn_dirty(pfn);
> - mark_page_dirty(kvm, gfn);
> - }
>
> if (fault_status != FSC_PERM && !device)
> clean_dcache_guest_page(pfn, vma_pagesize);
> @@ -911,6 +908,19 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> memcache);
> }
>
> + /* Mark the page dirty only if the fault is handled successfully */
> + if (writable && !ret) {
> + kvm_set_pfn_dirty(pfn);
> + mark_page_dirty(kvm, gfn);
> + }
> +
> + /* Let the guest directly enter again if we were trying to recreate the
> + * same mapping or only change access permissions with BBM, which is not
> + * permitted in the mapping path.
> + */
> + if (ret == -EAGAIN)
> + ret = 0;
Maybe just 'return ret != -EAGAIN ? ret : 0;' at the end of the function?
Will
On 2021/1/13 23:51, Will Deacon wrote:
> On Wed, Dec 16, 2020 at 08:28:44PM +0800, Yanan Wang wrote:
>> We now mark the page dirty and set the bitmap before calling fault handlers
>> in user_mem_abort(), and we might end up having spurious dirty pages if
>> update of permissions or mapping has failed.
>> So, mark the page dirty only if the fault is handled successfully.
>>
>> Let the guest directly enter again but not return to userspace if we were
>> trying to recreate the same mapping or only change access permissions
>> with BBM, which is not permitted in the mapping path.
>>
>> Signed-off-by: Yanan Wang <[email protected]>
>> ---
>> arch/arm64/kvm/mmu.c | 18 ++++++++++++++----
>> 1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 75814a02d189..72e516a10914 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -879,11 +879,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> if (vma_pagesize == PAGE_SIZE && !force_pte)
>> vma_pagesize = transparent_hugepage_adjust(memslot, hva,
>> &pfn, &fault_ipa);
>> - if (writable) {
>> + if (writable)
>> prot |= KVM_PGTABLE_PROT_W;
>> - kvm_set_pfn_dirty(pfn);
>> - mark_page_dirty(kvm, gfn);
>> - }
>>
>> if (fault_status != FSC_PERM && !device)
>> clean_dcache_guest_page(pfn, vma_pagesize);
>> @@ -911,6 +908,19 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> memcache);
>> }
>>
>> + /* Mark the page dirty only if the fault is handled successfully */
>> + if (writable && !ret) {
>> + kvm_set_pfn_dirty(pfn);
>> + mark_page_dirty(kvm, gfn);
>> + }
>> +
>> + /* Let the guest directly enter again if we were trying to recreate the
>> + * same mapping or only change access permissions with BBM, which is not
>> + * permitted in the mapping path.
>> + */
>> + if (ret == -EAGAIN)
>> + ret = 0;
> Maybe just 'return ret != -EAGAIN ? ret : 0;' at the end of the function?
Yes, it's more concise.