On 05/29/2018 02:22 PM, Oleksandr Andrushchenko wrote:
> On 05/29/2018 09:04 PM, Boris Ostrovsky wrote:
>> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
>> @@ -463,11 +457,6 @@ static enum bp_state
>> increase_reservation(unsigned long nr_pages)
>> int rc;
>> unsigned long i;
>> struct page *page;
>> - struct xen_memory_reservation reservation = {
>> - .address_bits = 0,
>> - .extent_order = EXTENT_ORDER,
>> - .domid = DOMID_SELF
>> - };
>> if (nr_pages > ARRAY_SIZE(frame_list))
>> nr_pages = ARRAY_SIZE(frame_list);
>> @@ -486,9 +475,7 @@ static enum bp_state
>> increase_reservation(unsigned long nr_pages)
>> page = balloon_next_page(page);
>> }
>> - set_xen_guest_handle(reservation.extent_start, frame_list);
>> - reservation.nr_extents = nr_pages;
>> - rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
>> + rc = xenmem_reservation_increase(nr_pages, frame_list);
>> if (rc <= 0)
>> return BP_EAGAIN;
>> @@ -496,29 +483,7 @@ static enum bp_state
>> increase_reservation(unsigned long nr_pages)
>> page = balloon_retrieve(false);
>> BUG_ON(page == NULL);
>> -#ifdef CONFIG_XEN_HAVE_PVMMU
>> - /*
>> - * We don't support PV MMU when Linux and Xen is using
>> - * different page granularity.
>> - */
>> - BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
>> -
>> - if (!xen_feature(XENFEAT_auto_translated_physmap)) {
>> - unsigned long pfn = page_to_pfn(page);
>> -
>> - set_phys_to_machine(pfn, frame_list[i]);
>> -
>> - /* Link back into the page tables if not highmem. */
>> - if (!PageHighMem(page)) {
>> - int ret;
>> - ret = HYPERVISOR_update_va_mapping(
>> - (unsigned long)__va(pfn << PAGE_SHIFT),
>> - mfn_pte(frame_list[i], PAGE_KERNEL),
>> - 0);
>> - BUG_ON(ret);
>> - }
>> - }
>> -#endif
>> + xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
>>
>> Can you make a single call to xenmem_reservation_va_mapping_update(rc,
>> ...)? You need to keep track of pages but presumable they can be put
>> into an array (or a list). In fact, perhaps we can have
>> balloon_retrieve() return a set of pages.
> This is actually how it is used later on for dma-buf, but I just
> didn't want
> to alter original balloon code too much, but this can be done, in
> order of simplicity:
>
> 1. Similar to frame_list, e.g. static array of struct page* of size
> ARRAY_SIZE(frame_list):
> more static memory is used, but no allocations
>
> 2. Allocated at run-time with kcalloc: allocation can fail
If this is called in freeing DMA buffer code path or in error path then
we shouldn't do it.
>
> 3. Make balloon_retrieve() return a set of pages: will require
> list/array allocation
> and handling, allocation may fail, balloon_retrieve prototype change
balloon pages are strung on the lru list. Can we keep have
balloon_retrieve return a list of pages on that list?
-boris
>
> Could you please tell which of the above will fit better?
>
>>
>>
