Re: [Qemu-devel] [PATCH v1] exec: handle NULL pointer in flatview_read_continue

[Paolo Bonzini]

On 09/08/2018 17:03, Paolo Bonzini wrote:
> On 09/08/2018 16:55, Olaf Hering wrote:
>>
>>> I think the simplest fix is for the map
>>> cache to set aside a zero page and return it whenever it is asked for a
>>> ballooned page.
>> Can qemu actually know if it ran into a ballooned page? I think no.
> 
> Well, xen_map_cache knows that it has run into *something like* a
> ballooned page when it returns NULL. :)

... however, that works for reading to the page, not writing.  The
problem is that your patch is incomplete.  There are many more callers
of qemu_ram_ptr_length, and none of them check the result.

Paolo