From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77430C7618B for ; Wed, 24 Jul 2019 06:58:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BA7A22BF3 for ; Wed, 24 Jul 2019 06:58:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="aZBHL++K" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726329AbfGXG6P (ORCPT ); Wed, 24 Jul 2019 02:58:15 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:41370 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725878AbfGXG6P (ORCPT ); Wed, 24 Jul 2019 02:58:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3X59uoIHWkle5151095EWlIhQ1uYulWqiYohiJvGIW0=; b=aZBHL++KElV7HejBz79l9aZpK WBi0+MfJWwUOWKC+kfJMHuYt2drkRJJ/IVSu/9T4E34Mg9lLPBX656A/Dtj3Sb3d2VaaMAdhHlRNz uCZgBsyiE3rx+f3LDhHCsXrQjn4NxUPdWaJQpa1l0QDJV/9bVb1/S6/IgNpEz9LdnlEioxXympEEX HWogf3lxQev2KnAtWlALsqZ5fsJ5YR1HnVc6I8AVM7o3ayY/RVD7tKO1eDsoOrkmIin578HoeQQVo sBzga0ZoDchy/8z6hJ5B+oSLxQNIgzOBbjsfhXnWXDKb528plA3SxBuvJB2atPh2HgVzJDS27j+Kh CexYiLXfA==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hqBE5-0006R9-MH; Wed, 24 Jul 2019 06:58:13 +0000 Date: Tue, 23 Jul 2019 23:58:13 -0700 From: Christoph Hellwig To: John Stultz Cc: Christoph Hellwig , lkml , Laura Abbott , Benjamin Gaignard , Sumit Semwal , Liam Mark , Pratik Patel , Brian Starkey , Vincent Donnefort , Sudipto Paul , "Andrew F . Davis" , Xu YiPing , "Chenfeng (puck)" , butao , "Xiaqing (A)" , Yudongbin , Chenbo Feng , Alistair Strachan , dri-devel , Hridya Valsaraju , Rob Clark Subject: Re: [PATCH v6 2/5] dma-buf: heaps: Add heap helpers Message-ID: <20190724065813.GB16225@infradead.org> References: <20190624194908.121273-1-john.stultz@linaro.org> <20190624194908.121273-3-john.stultz@linaro.org> <20190718100654.GA19666@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 22, 2019 at 09:09:25PM -0700, John Stultz wrote: > On Thu, Jul 18, 2019 at 3:06 AM Christoph Hellwig wrote: > > > > > +void INIT_HEAP_HELPER_BUFFER(struct heap_helper_buffer *buffer, > > > + void (*free)(struct heap_helper_buffer *)) > > > > Please use a lower case naming following the naming scheme for the > > rest of the file. > > Yes! Apologies as this was a hold-over from when the initialization > function was an inline function in the style of > INIT_WORK/INIT_LIST_HEAD. No longer appropriate that its a function. > I'll change it. > > > > +static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer) > > > +{ > > > + void *vaddr; > > > + > > > + vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL); > > > + if (!vaddr) > > > + return ERR_PTR(-ENOMEM); > > > + > > > + return vaddr; > > > +} > > > > Unless I'm misreading the patches this is used for the same pages that > > also might be dma mapped. In this case you need to use > > flush_kernel_vmap_range and invalidate_kernel_vmap_range in the right > > places to ensure coherency between the vmap and device view. Please > > also document the buffer ownership, as this really can get complicated. > > Forgive me I wasn't familiar with those calls, but this seems like it > would apply to all dma-buf exporters if so, and I don't see any > similar flush_kernel_vmap_range calls there (both functions are > seemingly only used by xfs, md and bio). > > We do have the dma_heap_dma_buf_begin_cpu_access()/dma_heap_dma_buf_end_cpu_access() > hooks (see more on these below) which sync the buffers for each > attachment (via dma_sync_sg_for_cpu/device), and are used around cpu > access to the buffers. Are you suggesting the > flush_kernel_vmap_range() call be added to those hooks or is the > dma_sync_sg_for_* calls sufficient there? dma_sync_sg_for_* only operates on the kernel direct mapping, that is what you get from page_address/kmap* for the page. But with vmap your create another alias in kernel virtual space, which dma_sync_sg_for_* can't know about. Now for most CPUs caches are indexed by physical addresses so this doesn't matter, but a significant minority of CPUs (parisc, some arm, some mips) index by virtual address, in which case we need non-empy flush_kernel_vmap_range and invalidate_kernel_vmap_range helper to deal with that vmap alias.