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X-UUID: 1173a46cb11f40ad99644152fce63674-20201124 Received: from mtkcas32.mediatek.inc [(172.27.4.253)] by mailgw02.mediatek.com (envelope-from ) (mailgw01.mediatek.com ESMTP with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 1399213662; Tue, 24 Nov 2020 17:24:46 +0800 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS32N2.mediatek.inc (172.27.4.72) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 24 Nov 2020 17:24:45 +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; Tue, 24 Nov 2020 17:24:43 +0800 Message-ID: <1606209884.26323.132.camel@mhfsdcap03> Subject: Re: [PATCH] iommu: Improve the performance for direct_mapping From: Yong Wu To: Will Deacon Date: Tue, 24 Nov 2020 17:24:44 +0800 In-Reply-To: <20201123123258.GC10233@willie-the-truck> References: <20201120090628.6566-1-yong.wu@mediatek.com> <20201123123258.GC10233@willie-the-truck> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: EBCB8F6C7AAB7CEFD384B30FE7D298E2FA4811C473B599035C7F59E811168DC42000:8 X-MTK: N Cc: youlin.pei@mediatek.com, anan.sun@mediatek.com, Nicolas Boichat , srv_heupstream@mediatek.com, chao.hao@mediatek.com, linux-kernel@vger.kernel.org, Krzysztof Kozlowski , Tomasz Figa , iommu@lists.linux-foundation.org, linux-mediatek@lists.infradead.org, Matthias Brugger , Robin Murphy , linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" 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: > > Currently direct_mapping always use the smallest pgsize which is SZ_4K > > normally to mapping. This is unnecessary. we could gather the size, and > > call iommu_map then, iommu_map could decide how to map better with the > > just right pgsize. > > > > From the original comment, we should take care overlap, otherwise, > > iommu_map may return -EEXIST. In this overlap case, we should map the > > previous region before overlap firstly. then map the left part. > > > > Each a iommu device will call this direct_mapping when its iommu > > initialize, This patch is effective to improve the boot/initialization > > time especially while it only needs level 1 mapping. > > > > Signed-off-by: Anan Sun > > Signed-off-by: Yong Wu > > --- > > drivers/iommu/iommu.c | 20 ++++++++++++++++++-- > > 1 file changed, 18 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > index df87c8e825f7..854a8fcb928d 100644 > > --- 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 unmapped_sz = 0; > > I think "unmapped" is the wrong word here, as this variable actually > represents the amount we want to map! I suggest "map_size" instead. > > > if (domain->ops->apply_resv_region) > > domain->ops->apply_resv_region(dev, domain, entry); > > @@ -752,10 +753,25 @@ 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) > > + if (phys_addr == 0) { > > + unmapped_sz += pg_size; /* Gather the size. */ > > continue; > > + } > > > > - ret = iommu_map(domain, addr, addr, pg_size, entry->prot); > > + if (unmapped_sz) { > > + /* Map the region before the overlap. */ > > + ret = iommu_map(domain, start, start, > > + unmapped_sz, entry->prot); > > + if (ret) > > + goto out; > > + start += unmapped_sz; > > I think it's a bit confusing to update start like this. Can we call > iommu_map(domain, addr - map_size, addr - map_size, map_size, entry->prot) > instead? > > > + 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 + addr += pg_size; /*Point to End */ + } - ret = iommu_map(domain, addr, addr, pg_size, entry->prot); - if (ret) - goto out; + if (map_size) { + ret = iommu_map(domain, addr - map_size, addr - map_size, + map_size, entry->prot); + if (ret) + goto out; + map_size = 0; + } } > > Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu