[PATCH v4 17/21] KVM: arm64: Convert user_mem_abort() to generic page-table API

[Marc Zyngier]

On 2020-09-10 11:51, Will Deacon wrote:
> On Wed, Sep 09, 2020 at 06:12:29PM +0100, Marc Zyngier wrote:
>> On 2020-09-09 15:20, Alexandru Elisei wrote:
>> > On 9/7/20 4:23 PM, Will Deacon wrote:
>> > > @@ -1610,62 +1605,31 @@ 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);
>> >
>> > The previous code called mark_page_dirty() only if the vma_pagesize ==
>> > PAGE_SIZE
>> > (and writable was true, obviously). Is this supposed to fix a bug?
>> 
>> No, this is actually introducing one. mark_page_dirty() checks that 
>> there is
>> an
>> associated bitmap, and thus only happens when writing to a single 
>> page, but
>> we
>> shouldn't do it for R/O memslots, which the current code avoids. It 
>> should
>> be
>> guarded by logging_active.
> 
> gfn_to_pfn_prot() will set "writable" to false for R/O memslots, so I 
> think
> we're good here.

Ah, good point.

         M.
-- 
Jazz is not dead. It just smells funny...