On 05/30/2018 06:20 PM, Boris Ostrovsky wrote:
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.
Then I would suggest we have it this way: current API requires that
struct page **pages are allocated from outside. So, let's allocate
the frames from outside as well. This way the caller is responsible for
both pages and frames arrays and API looks consistent.
+ 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.
Good, then this one is resolved
-boris
Thank you,
Oleksandr
