On 05/21/2018 01:32 PM, Oleksandr Andrushchenko wrote:
> On 05/21/2018 07:35 PM, Boris Ostrovsky wrote:
>> On 05/21/2018 01:40 AM, Oleksandr Andrushchenko wrote:
>>> 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@xxxxxxxx>
>>>> A commit message would be useful.
>>> Sure, v1 will have it
>>>>> Signed-off-by: Oleksandr Andrushchenko
>>>>> <oleksandr_andrushchenko@xxxxxxxx>
>>>>>
>>>>> 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?
>>
>> I am actually wondering how much of that code you end up reusing. You
>> pretty much create new code paths in both routines and common code ends
>> up being essentially the hypercall.
> Well, I hoped that it would be easier to maintain if I modify existing
> code
> to support both use-cases, but I am also ok to create new routines if
> this
> seems to be reasonable - please let me know
>> So the question is --- would it make
>> sense to do all of this separately from the balloon driver?
> This can be done, but which driver will host this code then? If we
> move from
> the balloon driver, then this could go to either gntdev or grant-table.
> What's your preference?
A separate module?
Is there any use for this feature outside of your zero-copy DRM driver?
-boris
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