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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618655513; bh=bKkHYDWEnUxH4+NZsQzc9XdOBx/eAasVlApeofpvQ3M=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=F8vK55v7UAeYClMXwewtQLHQ0TzAI75Gda/Ijyqb1bmDwdQP0a9qNJCXMN7YbFjAS dG8/5lw8Oh/K1rCPVqp5z1w7J4kKWAX0DkrnhWpkRSTuwOC7TPzuxif0+RqWn8cqRX pZUZxJgGN2u31XYsKolc/RRqCot3uzixXu+xCEwO9gitdkvxQC6D/X0UdL/QXE36np iD8Zr5qX8eqgiDJ8foVPlr+kPJNA1ItqyDhMGuNuBHDo9yh0U368iVOPkCABjyVsAC C3JEgc3qOIsozYto2rSELYyYwBSIA8CHj7yzKeDCuHRrrcWelfXpNbZ8dp+qY4qF47 TbQLKsvP+wzrw== Received: by mail-wr1-f48.google.com with SMTP id w4so25302220wrt.5 for ; Sat, 17 Apr 2021 03:31:53 -0700 (PDT) X-Gm-Message-State: AOAM531LzQdFTqvMNla2+65ax2Qtn8wiTY0Vn+PwwYEGfDf5JNSIQ9Eh htZPY4Eiuk5hbao/5mDXVreEloua+j9/A4GSwn0= X-Google-Smtp-Source: ABdhPJycE8LG0z9YxCgms5+k71EBmr9DkHzd41Oc6z9ytag0KDWOSXF5lk8cL6Kn2M30kai4QRK7X3xc1d9fGPyxl30= X-Received: by 2002:adf:db4f:: with SMTP id f15mr3734418wrj.99.1618655512568; Sat, 17 Apr 2021 03:31:52 -0700 (PDT) MIME-Version: 1.0 References: <20210410205246.507048-2-willy@infradead.org> <20210411114307.5087f958@carbon> <20210411103318.GC2531743@casper.infradead.org> <20210412011532.GG2531743@casper.infradead.org> <20210414101044.19da09df@carbon> <20210414115052.GS2531743@casper.infradead.org> <20210414211322.3799afd4@carbon> <20210414213556.GY2531743@casper.infradead.org> <20210415200832.32796445@carbon> <20210416152755.GL2531743@casper.infradead.org> In-Reply-To: <20210416152755.GL2531743@casper.infradead.org> From: Arnd Bergmann Date: Sat, 17 Apr 2021 12:31:37 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems To: Matthew Wilcox Cc: Jesper Dangaard Brouer , Grygorii Strashko , "netdev@vger.kernel.org" , Ilias Apalodimas , "linux-kernel@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linux-mm@kvack.org" , David Laight , Matteo Croce , "linuxppc-dev@lists.ozlabs.org" , Christoph Hellwig , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9C52BA0000FF X-Stat-Signature: 3h5kutmpz5dzb1h8uf5wm47w7pan4y9y Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf07; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618655514-144533 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 16, 2021 at 5:27 PM Matthew Wilcox wrote: > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > index b5b195305346..db7c7020746a 100644 > --- a/include/net/page_pool.h > +++ b/include/net/page_pool.h > @@ -198,7 +198,17 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, > > static inline dma_addr_t page_pool_get_dma_addr(struct page *page) > { > - return page->dma_addr; > + dma_addr_t ret = page->dma_addr[0]; > + if (sizeof(dma_addr_t) > sizeof(unsigned long)) > + ret |= (dma_addr_t)page->dma_addr[1] << 32; > + return ret; > +} Have you considered using a PFN type address here? I suspect you can prove that shifting the DMA address by PAGE_BITS would make it fit into an 'unsigned long' on all 32-bit architectures with 64-bit dma_addr_t. This requires that page->dma_addr to be page aligned, as well as fit into 44 bits. I recently went through the maximum address space per architecture to define a MAX_POSSIBLE_PHYSMEM_BITS, and none of them have more than 40 here, presumably the same is true for dma address space. Arnd