On 2023/8/16 19:26, Ilias Apalodimas wrote: > Hi Yunsheng > > On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote: >> >> Currently page_pool_alloc_frag() is not supported in 32-bit >> arch with 64-bit DMA because of the overlap issue between >> pp_frag_count and dma_addr_upper in 'struct page' for those >> arches, which seems to be quite common, see [1], which means >> driver may need to handle it when using frag API. > > That wasn't so common. IIRC it was a single TI platform that was breaking? I am not so sure about that as grepping 'ARM_LPAE' has a long list for that. > >> >> In order to simplify the driver's work when using frag API >> this patch allows page_pool_alloc_frag() to call >> page_pool_alloc_pages() to return pages for those arches. > > Do we have any use cases of people needing this? Those architectures > should be long dead and although we have to support them in the > kernel, I don't personally see the advantage of adjusting the API to > do that. Right now we have a very clear separation between allocating > pages or fragments. Why should we hide a page allocation under a > frag allocation? A driver writer can simply allocate pages for those > boards. Am I the only one not seeing a clean win here? It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag in this patchset. > > Thanks > /Ilias >
