Re: [Xen-devel] [PATCH] x86/mm: Make PV linear pagetables optional

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.10.17 at 12:22, <george.dunlap@xxxxxxxxxx> wrote:
> On 10/18/2017 10:39 AM, Jan Beulich wrote:
>>>>> On 17.10.17 at 19:10, <george.dunlap@xxxxxxxxxx> wrote:
>>> @@ -2330,8 +2360,8 @@ static int _put_page_type(struct page_info *page, 
>>> bool preemptible,
>>>                   * necessary anymore for a dying domain.
>>>                   */
>>>                  ASSERT(page_get_owner(page)->is_dying);
>>> -                ASSERT(page->linear_pt_count < 0);
>>> -                ASSERT(ptpg->linear_pt_count > 0);
>>> +                LPT_ASSERT(page->linear_pt_count < 0);
>>> +                LPT_ASSERT(ptpg->linear_pt_count > 0);
>> 
>> Other than Andrew has suggested, with these I don't think
>> LPT_ASSERT() can go away, unless you played tricks and forced
>> the function's ptpg to be NULL regardless of caller, or unless you
>> put the entire if() into an #ifdef.
> 
> Actually, coming back to this -- if we disable linear pagetables, how
> can it ever be the case that "PGT_type_equal(x,
> ptpg->u.inuse.type_info)" evaluates to true?  The ASSERT()s should never
> be executed.

Oh, indeed. I.e. taking it from the other angle - the ASSERT()s
being reached, it would be correct for them to always trigger.

Jan


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