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Wed, 25 Nov 2020 03:13:33 -0800 Received: from MTKMBS31N1.mediatek.inc (172.27.4.69) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 25 Nov 2020 03:03:36 -0800 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N1.mediatek.inc (172.27.4.69) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 25 Nov 2020 19:03:34 +0800 Received: from [10.17.3.153] (10.17.3.153) by MTKCAS36.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 25 Nov 2020 19:03:33 +0800 Message-ID: <1606302214.26323.141.camel@mhfsdcap03> Subject: Re: [PATCH] iommu: Improve the performance for direct_mapping From: Yong Wu To: Will Deacon Date: Wed, 25 Nov 2020 19:03:34 +0800 In-Reply-To: <20201124110520.GA12980@willie-the-truck> References: <20201120090628.6566-1-yong.wu@mediatek.com> <20201123123258.GC10233@willie-the-truck> <1606209884.26323.132.camel@mhfsdcap03> <20201124110520.GA12980@willie-the-truck> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: 3E37F2948B73A16F8990BEF5FB644CD56B780219D1EF19A777FBD0308C48F13A2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201125_061349_667379_96755502 X-CRM114-Status: GOOD ( 28.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: youlin.pei@mediatek.com, anan.sun@mediatek.com, Nicolas Boichat , srv_heupstream@mediatek.com, Tomasz Figa , Joerg Roedel , linux-kernel@vger.kernel.org, Krzysztof Kozlowski , chao.hao@mediatek.com, iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, Matthias Brugger , Robin Murphy , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 2020-11-24 at 11:05 +0000, Will Deacon wrote: > On Tue, Nov 24, 2020 at 05:24:44PM +0800, Yong Wu wrote: > > On Mon, 2020-11-23 at 12:32 +0000, Will Deacon wrote: > > > On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote: > > > > + unmapped_sz = 0; > > > > + } > > > > + start += pg_size; > > > > + } > > > > + if (unmapped_sz) { > > > > + ret = iommu_map(domain, start, start, unmapped_sz, > > > > + entry->prot); > > > > > > Can you avoid this hunk by changing your loop check to something like: > > > > > > if (!phys_addr) { > > > map_size += pg_size; > > > if (addr + pg_size < end) > > > continue; > > > } > > > > Thanks for your quick review. I have fixed and tested it. the patch is > > simple. I copy it here. Is this readable for you now? > > > > > > --- a/drivers/iommu/iommu.c > > +++ b/drivers/iommu/iommu.c > > @@ -737,6 +737,7 @@ static int > > iommu_create_device_direct_mappings(struct iommu_group *group, > > /* We need to consider overlapping regions for different devices */ > > list_for_each_entry(entry, &mappings, list) { > > dma_addr_t start, end, addr; > > + size_t map_size = 0; > > > > if (domain->ops->apply_resv_region) > > domain->ops->apply_resv_region(dev, domain, entry); > > @@ -752,12 +753,21 @@ static int > > iommu_create_device_direct_mappings(struct iommu_group *group, > > phys_addr_t phys_addr; > > > > phys_addr = iommu_iova_to_phys(domain, addr); > > - if (phys_addr) > > - continue; > > + if (!phys_addr) { > > + map_size += pg_size; > > + if (addr + pg_size < end) > > + continue; > > + else > > You don't need the 'else' here ^^^ > > > + addr += pg_size; /*Point to End */ > > addr = end ? > > That said, maybe we could simplify this further by changing the loop bounds > to be: > > for (addr = start; addr <= end; addr += pg_size) > > and checking: > > if (!phys_addr && addr != end) { > map_size += pg_size; > continue; > } > > does that work? It works but I think we can not check iommu_iova_to_phys(domain, end). We should add a "if", like: for (addr = start; addr <= end; addr += pg_size) { ... if (addr < end) { phys_addr = iommu_iova_to_phys(domain, addr); if (!phys_addr) { map_size += pg_size; continue; } } ... If you don't like this "if (addr < end)", then we have to add a "goto". like this: for (addr = start; addr <= end; addr += pg_size) { phys_addr_t phys_addr; if (addr == end) goto map_last; phys_addr = iommu_iova_to_phys(domain, addr); if (!phys_addr) { map_size += pg_size; continue; } map_last: if (!map_size) continue; ret = iommu_map(domain, addr - map_size, addr - map_size, map_size, entry->prot); if (ret) goto out; } Which one is better? > > Will > > _______________________________________________ > Linux-mediatek mailing list > Linux-mediatek@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-mediatek _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel