Re: [Xen-devel] [PATCH for-4.9] x86/mm: Fix incorrect unmapping of 2MB and 1GB pages

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 10/05/17 11:26, Jan Beulich wrote:
>>>> On 10.05.17 at 11:43, <igor.druzhinin@xxxxxxxxxx> wrote:
>> --- a/xen/arch/x86/mm/p2m-ept.c
>> +++ b/xen/arch/x86/mm/p2m-ept.c
>> @@ -681,6 +681,7 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
>> mfn_t mfn,
>>      ept_entry_t *table, *ept_entry = NULL;
>>      unsigned long gfn_remainder = gfn;
>>      unsigned int i, target = order / EPT_TABLE_ORDER;
>> +    unsigned long mfn_mask = mfn_valid(mfn) ? mfn_x(mfn) : 0;
> 
> Aiui MMIO pages will come here too, so an mfn_valid() check here
> (and below) is too lax.

The resulting order will never be higher than the order passed in by the
caller.  Assuming that the caller is setting an entire 2MiB (or 1GiB)
region as MMIO, is it not valid to set a 2MiB or 1GiB entry as such?
The code seems to be written in such a way that such entries are expected.

 -George


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