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Message-ID: <20250718011407.GB38833@system.software.com>
Date: Fri, 18 Jul 2025 10:14:07 +0900
From: Byungchul Park <byungchul@...com>
To: kernel test robot <lkp@...el.com>
Cc: willy@...radead.org, netdev@...r.kernel.org,
oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, kernel_team@...ynix.com, almasrymina@...gle.com,
ilias.apalodimas@...aro.org, harry.yoo@...cle.com,
akpm@...ux-foundation.org, andrew+netdev@...n.ch,
asml.silence@...il.com, toke@...hat.com, david@...hat.com,
Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org,
surenb@...gle.com, mhocko@...e.com, linux-rdma@...r.kernel.org,
bpf@...r.kernel.org, vishal.moola@...il.com, hannes@...xchg.org,
ziy@...dia.com, jackmanb@...gle.com, wei.fang@....com,
shenwei.wang@....com, xiaoning.wang@....com, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org
Subject: Re: [Intel-wired-lan] [PATCH net-next v11 12/12] libeth: xdp: access
->pp through netmem_desc instead of page
On Fri, Jul 18, 2025 at 09:43:46AM +0900, Byungchul Park wrote:
> On Fri, Jul 18, 2025 at 01:42:38AM +0800, kernel test robot wrote:
> > Hi Byungchul,
> >
> > kernel test robot noticed the following build warnings:
> >
> > [auto build test WARNING on c65d34296b2252897e37835d6007bbd01b255742]
> >
> > url: https://github.com/intel-lab-lkp/linux/commits/Byungchul-Park/netmem-introduce-struct-netmem_desc-mirroring-struct-page/20250717-150253
> > base: c65d34296b2252897e37835d6007bbd01b255742
> > patch link: https://lore.kernel.org/r/20250717070052.6358-13-byungchul%40sk.com
> > patch subject: [Intel-wired-lan] [PATCH net-next v11 12/12] libeth: xdp: access ->pp through netmem_desc instead of page
> > config: arm-randconfig-r072-20250717 (https://download.01.org/0day-ci/archive/20250718/202507180111.jygqJHzk-lkp@intel.com/config)
> > compiler: arm-linux-gnueabi-gcc (GCC) 8.5.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250718/202507180111.jygqJHzk-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@...el.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202507180111.jygqJHzk-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> > In file included from include/linux/container_of.h:5,
> > from include/linux/list.h:5,
> > from include/linux/timer.h:5,
> > from include/linux/netdevice.h:24,
> > from include/trace/events/xdp.h:8,
> > from include/linux/bpf_trace.h:5,
> > from include/net/libeth/xdp.h:7,
> > from drivers/net/ethernet/intel/libeth/tx.c:6:
> > include/net/libeth/xdp.h: In function 'libeth_xdp_prepare_buff':
> > >> include/net/libeth/xdp.h:1295:23: warning: passing argument 1 of 'page_pool_page_is_pp' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
> > pp_page_to_nmdesc(page)->pp->p.offset, len, true);
> > ^~~~
> > include/linux/build_bug.h:30:63: note: in definition of macro 'BUILD_BUG_ON_INVALID'
> > #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
> > ^
> > include/net/netmem.h:301:2: note: in expansion of macro 'DEBUG_NET_WARN_ON_ONCE'
> > DEBUG_NET_WARN_ON_ONCE(!page_pool_page_is_pp(p)); \
> > ^~~~~~~~~~~~~~~~~~~~~~
> > include/net/libeth/xdp.h:1295:5: note: in expansion of macro 'pp_page_to_nmdesc'
> > pp_page_to_nmdesc(page)->pp->p.offset, len, true);
> > ^~~~~~~~~~~~~~~~~
> > In file included from arch/arm/include/asm/cacheflush.h:10,
> > from include/linux/cacheflush.h:5,
> > from include/linux/highmem.h:8,
> > from include/linux/bvec.h:10,
> > from include/linux/skbuff.h:17,
> > from include/net/net_namespace.h:43,
> > from include/linux/netdevice.h:38,
> > from include/trace/events/xdp.h:8,
> > from include/linux/bpf_trace.h:5,
> > from include/net/libeth/xdp.h:7,
> > from drivers/net/ethernet/intel/libeth/tx.c:6:
> > include/linux/mm.h:4176:54: note: expected 'struct page *' but argument is of type 'const struct page *'
> > static inline bool page_pool_page_is_pp(struct page *page)
> > ~~~~~~~~~~~~~^~~~
>
> Oh. page_pool_page_is_pp() in the mainline code already has this issue
> that the helper cannot take const struct page * as argument.
>
> How should we resolve the issue? Changing page_pool_page_is_pp() to
> macro and using _Generic again looks too much. Or should we? Any idea?
option 1. Remove 'const' on declaration of struct page in
libeth_xdp_prepare_buff() but maybe bad.
option 2. Use __pp_page_to_nmdesc() instead of pp_page_to_nmdesc() in
libeth_xdp_prepare_buff() to skip checking if it's a pp page.
option 3. Change page_pool_page_is_pp() to macro and use _Generic to
cover const casting.
More?
Byungchul
> Byungchul
>
> > vim +1295 include/net/libeth/xdp.h
> >
> > 1263
> > 1264 bool libeth_xdp_buff_add_frag(struct libeth_xdp_buff *xdp,
> > 1265 const struct libeth_fqe *fqe,
> > 1266 u32 len);
> > 1267
> > 1268 /**
> > 1269 * libeth_xdp_prepare_buff - fill &libeth_xdp_buff with head FQE data
> > 1270 * @xdp: XDP buffer to attach the head to
> > 1271 * @fqe: FQE containing the head buffer
> > 1272 * @len: buffer len passed from HW
> > 1273 *
> > 1274 * Internal, use libeth_xdp_process_buff() instead. Initializes XDP buffer
> > 1275 * head with the Rx buffer data: data pointer, length, headroom, and
> > 1276 * truesize/tailroom. Zeroes the flags.
> > 1277 * Uses faster single u64 write instead of per-field access.
> > 1278 */
> > 1279 static inline void libeth_xdp_prepare_buff(struct libeth_xdp_buff *xdp,
> > 1280 const struct libeth_fqe *fqe,
> > 1281 u32 len)
> > 1282 {
> > 1283 const struct page *page = __netmem_to_page(fqe->netmem);
> > 1284
> > 1285 #ifdef __LIBETH_WORD_ACCESS
> > 1286 static_assert(offsetofend(typeof(xdp->base), flags) -
> > 1287 offsetof(typeof(xdp->base), frame_sz) ==
> > 1288 sizeof(u64));
> > 1289
> > 1290 *(u64 *)&xdp->base.frame_sz = fqe->truesize;
> > 1291 #else
> > 1292 xdp_init_buff(&xdp->base, fqe->truesize, xdp->base.rxq);
> > 1293 #endif
> > 1294 xdp_prepare_buff(&xdp->base, page_address(page) + fqe->offset,
> > > 1295 pp_page_to_nmdesc(page)->pp->p.offset, len, true);
> > 1296 }
> > 1297
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
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