Avi Kivity wrote:
> Anthony Liguori wrote:
>
>> This patch allows VMA's that contain no backing page to be used for guest
>> memory. This is a drop-in replacement for Ben-Ami's first page in his direct
>> mmio series. Here, we continue to allow mmio pages to be represented in the
>> rmap.
>>
>>
>>
>
> I like this very much, as it only affects accessors and not the mmu core
> itself.
>
> Hollis/Xiantao/Carsten, can you confirm that this approach works for
> you? Carsten, I believe you don't have mmio, but at least this
> shouldn't interfere.
>
>
>>
>> struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
>> {
>> - return pfn_to_page(gfn_to_pfn(kvm, gfn));
>> + pfn_t pfn;
>> +
>> + pfn = gfn_to_pfn(kvm, gfn);
>> + if (pfn_valid(pfn))
>> + return pfn_to_page(pfn);
>> +
>> + return NULL;
>> }
>>
>>
>
> You're returning NULL here, not bad_page.
>
My thinking was that bad_page indicates that the gfn is invalid. This
is a different type of error though. The problem is that the guest is
we are trying to kmap() a page that has no struct page associated with
it. I'm not sure what the right thing to do here is.
Perhaps we should be replacing consumers of gfn_to_page() with
copy_to_user() instead?
Regards,
Anthony Liguori
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