Re: [Xen-devel] [PATCH v7 4/5] ix86/ioreq server: Asynchronously reset outstanding p2m_ioreq_server entries.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.03.17 at 08:42, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
> On 3/13/2017 7:24 PM, Jan Beulich wrote:
>>>>> On 11.03.17 at 09:42, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
>>> On 3/11/2017 12:03 AM, Jan Beulich wrote:
>>>> But there's a wider understanding issue I'm having here: What is
>>>> an "entry" here? Commonly I would assume this to refer to an
>>>> individual (4k) page, but it looks like you really mean table entry,
>>>> i.e. possibly representing a 2M or 1G page.
>>> Well, it should be an entry pointing to a 4K page(only).
>>> For p2m_ioreq_server, we shall not meet huge page. Because they are
>>> changed from p2m_ram_rw pages
>>> in set_mem_type() -> p2m_change_type_one(), which calls p2m_set_entry()
>>> with PAGE_ORDER_4K specified.
>> And recombination of large pages won't ever end up hitting these?
> 
> Well, by recombination I guess you refer to the POD pages? I do not 
> think p2m_ioreq_server
> pages will be combined now, which means we do not need to worry about 
> recounting the
> p2m_ioreq_server entries while a split happens.

No, I didn't think about PoD here. But indeed I was misremembering:
We don't currently make any attempt to transparently recreate large
pages.

Jan


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