On 05/30/2018 02:34 AM, Oleksandr Andrushchenko wrote:
> On 05/29/2018 10:10 PM, Boris Ostrovsky wrote:
>> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
>> +/**
>> + * gnttab_dma_free_pages - free DMAable pages
>> + * @args: arguments to the function
>> + */
>> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
>> +{
>> + xen_pfn_t *frames;
>> + size_t size;
>> + int i, ret;
>> +
>> + gnttab_pages_clear_private(args->nr_pages, args->pages);
>> +
>> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL);
>>
>> Any way you can do it without allocating memory? One possibility is to
>> keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like
>> that either but it's the only thing I can think of).
> Yes, I was also thinking about storing the allocated frames array from
> gnttab_dma_alloc_pages(), but that seemed not to be clear enough as
> the caller of the gnttab_dma_alloc_pages will need to store those frames
> in some context, so we can pass them on free. But the caller doesn't
> really
> need the frames which might confuse, so I decided to make those
> allocations
> on the fly.
> But I can still rework that to store the frames if you insist: please
> let me know.
I would prefer not to allocate anything in the release path. Yes, I
realize that dragging frames array around is not necessary but IMO it's
better than potentially failing an allocation during a teardown. A
comment in the struct definition could explain the reason for having
this field.
>>
>>
>>> + if (!frames)
>>> + return -ENOMEM;
>>> +
>>> + for (i = 0; i < args->nr_pages; i++)
>>> + frames[i] = page_to_xen_pfn(args->pages[i]);
>>
>> Not xen_page_to_gfn()?
> Well, according to [1] it should be :
> /* XENMEM_populate_physmap requires a PFN based on Xen
> * granularity.
> */
> frame_list[i] = page_to_xen_pfn(page);
Ah, yes. I was looking at decrease_reservation and automatically assumed
the same parameter type.
-boris
