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[87.59.106.155]) by smtp.gmail.com with ESMTPSA id l9sm172205ljg.44.2021.09.23.02.33.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Sep 2021 02:33:29 -0700 (PDT) From: Jesper Dangaard Brouer X-Google-Original-From: Jesper Dangaard Brouer Cc: brouer@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linuxarm@openeuler.org, hawk@kernel.org, ilias.apalodimas@linaro.org, jonathan.lemon@gmail.com, alobakin@pm.me, willemb@google.com, cong.wang@bytedance.com, pabeni@redhat.com, haokexin@gmail.com, nogikh@google.com, elver@google.com, memxor@gmail.com, edumazet@google.com, alexander.duyck@gmail.com, dsahern@gmail.com Subject: Re: [PATCH net-next 1/7] page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA To: Yunsheng Lin , davem@davemloft.net, kuba@kernel.org References: <20210922094131.15625-1-linyunsheng@huawei.com> <20210922094131.15625-2-linyunsheng@huawei.com> Message-ID: <0ffa15a1-742d-a05d-3ea6-04ff25be6a29@redhat.com> Date: Thu, 23 Sep 2021 11:33:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210922094131.15625-2-linyunsheng@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 22/09/2021 11.41, Yunsheng Lin wrote: > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 1a6978427d6c..a65bd7972e37 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -49,6 +49,12 @@ static int page_pool_init(struct page_pool *pool, > * which is the XDP_TX use-case. > */ > if (pool->p.flags & PP_FLAG_DMA_MAP) { > + /* DMA-mapping is not supported on 32-bit systems with > + * 64-bit DMA mapping. > + */ > + if (sizeof(dma_addr_t) > sizeof(unsigned long)) > + return -EINVAL; As I said before, can we please use another error than EINVAL. We should give drivers a chance/ability to detect this error, and e.g. fallback to doing DMA mappings inside driver instead. I suggest using EOPNOTSUPP 95 (Operation not supported). -Jesper