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SubjectRe: [Xen-devel] [RFC 1/3] xen/balloon: Allow allocating DMA buffers
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On 05/19/2018 01:04 AM, Boris Ostrovsky wrote:
> On 05/17/2018 04:26 AM, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> A commit message would be useful.
Sure, v1 will have it
>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> for (i = 0; i < nr_pages; i++) {
>> - page = alloc_page(gfp);
>> - if (page == NULL) {
>> - nr_pages = i;
>> - state = BP_EAGAIN;
>> - break;
>> + if (ext_pages) {
>> + page = ext_pages[i];
>> + } else {
>> + page = alloc_page(gfp);
>> + if (page == NULL) {
>> + nr_pages = i;
>> + state = BP_EAGAIN;
>> + break;
>> + }
>> }
>> scrub_page(page);
>> list_add(&page->lru, &pages);
>> @@ -529,7 +565,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>> i = 0;
>> list_for_each_entry_safe(page, tmp, &pages, lru) {
>> /* XENMEM_decrease_reservation requires a GFN */
>> - frame_list[i++] = xen_page_to_gfn(page);
>> + frames[i++] = xen_page_to_gfn(page);
>>
>> #ifdef CONFIG_XEN_HAVE_PVMMU
>> /*
>> @@ -552,18 +588,22 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
>> #endif
>> list_del(&page->lru);
>>
>> - balloon_append(page);
>> + if (!ext_pages)
>> + balloon_append(page);
>
> So what you are proposing is not really ballooning. You are just
> piggybacking on existing interfaces, aren't you?
Sort of. Basically I need to {increase|decrease}_reservation, not actually
allocating ballooned pages.
Do you think I can simply EXPORT_SYMBOL for {increase|decrease}_reservation?
Any other suggestion?
> -boris
>
>
Thank you,
Oleksandr

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