Re: [PATCH] kvm, x86: Properly check whether a pfn is an MMIO or not

[Paolo Bonzini]

On 15/09/2016 18:04, Kani, Toshimitsu wrote:
> On Thu, 2016-09-15 at 08:22 +0200, Paolo Bonzini wrote:
>>
>> On 15/09/2016 07:54, Raslan, KarimAllah wrote:
>>>
>>>
>>>>
>>>> On Jun 22, 2016, at 3:41 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx>
>>>> wrote:
>>>>
>>>>
>>>>
>>>> On 22/06/2016 04:34, KarimAllah Ahmed wrote:
>>>>>
>>>>> pfn_valid check is not sufficient because it only checks if a
>>>>> page has a struct page or not, if for example "mem=" was passed
>>>>> to the kernel some valid pages won't have a struct page. This
>>>>> means that if guests were assigned valid memory that lies after
>>>>> the mem= boundary it will be passed uncached to the guest no
>>>>> matter what the guest caching attributes are for this memory.
>>>>
>>>> How can you pass memory after the mem= boundary to the guest?
>>>
>>> Does my previous reply answer your question?
>>
>> Yes, but I'm not sure it's the right way to do it.  Looking at the
>> e820 memory map seems pretty hacky.
> 
> Can you use region_intersects() for this check?  See memremap() as an
> example using this interface.

This one seems more generic but very slow.

Paolo