From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v3 3/7] iommu/mediatek: Use gather to achieve the tlb range flush Date: Tue, 15 Oct 2019 12:38:35 +0100 Message-ID: <5d03ebcb-0cd1-a9ad-0f4e-c219e351396c@arm.com> References: <1571035101-4213-1-git-send-email-yong.wu@mediatek.com> <1571035101-4213-4-git-send-email-yong.wu@mediatek.com> <1571117166.19130.83.camel@mhfsdcap03> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1571117166.19130.83.camel@mhfsdcap03> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Yong Wu Cc: Matthias Brugger , Joerg Roedel , Will Deacon , Evan Green , Tomasz Figa , linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, youlin.pei@mediatek.com, Nicolas Boichat , anan.sun@mediatek.com, cui.zhang@mediatek.com, chao.hao@mediatek.com, edison.hsieh@mediatek.com List-Id: linux-mediatek@lists.infradead.org On 15/10/2019 06:26, Yong Wu wrote: > On Mon, 2019-10-14 at 15:21 +0100, Robin Murphy wrote: >> On 14/10/2019 07:38, Yong Wu wrote: >>> Use the iommu_gather mechanism to achieve the tlb range flush. >>> Gather the iova range in the "tlb_add_page", then flush the merged iova >>> range in iotlb_sync. >>> >>> Note: If iotlb_sync comes from iommu_iotlb_gather_add_page, we have to >>> avoid retry the lock since the spinlock have already been acquired. >> >> I think this could probably be even simpler - once the actual >> register-poking is all confined to mtk_iommu_tlb_sync(), you should be >> able get rid of the per-domain locking in map/unmap and just have a >> single per-IOMMU lock to serialise syncs. The io-pgtable code itself >> hasn't needed external locking for a while now. > > This is more simpler! Thanks very much. I will try this. > > The only concern is there is no lock in the iova_to_phys then, maybe use > the new lock instead. iova_to_phys isn't issuing any syncs, so you don't need any locking there - if anyone calls that in a way which races against the given address being unmapped and remapped they can't expect a meaningful result anyway. Robin. >>> Suggested-by: Tomasz Figa >>> Signed-off-by: Yong Wu >>> --- >>> 1) This is the special case backtrace: >>> >>> mtk_iommu_iotlb_sync+0x50/0xa0 >>> mtk_iommu_tlb_flush_page_nosync+0x5c/0xd0 >>> __arm_v7s_unmap+0x174/0x598 >>> arm_v7s_unmap+0x30/0x48 >>> mtk_iommu_unmap+0x50/0x78 >>> __iommu_unmap+0xa4/0xf8 >>> >>> 2) The checking "if (gather->start == ULONG_MAX) return;" also is >>> necessary. It will happened when unmap only go to _flush_walk, then >>> enter this tlb_sync. >>> --- >>> drivers/iommu/mtk_iommu.c | 29 +++++++++++++++++++++++++---- >>> drivers/iommu/mtk_iommu.h | 1 + >>> 2 files changed, 26 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c >>> index 5f594d6..8712afc 100644 >>> --- a/drivers/iommu/mtk_iommu.c >>> +++ b/drivers/iommu/mtk_iommu.c >>> @@ -234,7 +234,12 @@ static void mtk_iommu_tlb_flush_page_nosync(struct iommu_iotlb_gather *gather, >>> unsigned long iova, size_t granule, >>> void *cookie) >>> { >>> - mtk_iommu_tlb_add_flush_nosync(iova, granule, granule, true, cookie); >>> + struct mtk_iommu_data *data = cookie; >>> + struct iommu_domain *domain = &data->m4u_dom->domain; >>> + >>> + data->is_in_tlb_gather_add_page = true; >>> + iommu_iotlb_gather_add_page(domain, gather, iova, granule); >>> + data->is_in_tlb_gather_add_page = false; >>> } >>> >>> static const struct iommu_flush_ops mtk_iommu_flush_ops = { >>> @@ -453,12 +458,28 @@ static void mtk_iommu_flush_iotlb_all(struct iommu_domain *domain) >>> static void mtk_iommu_iotlb_sync(struct iommu_domain *domain, >>> struct iommu_iotlb_gather *gather) >>> { >>> + struct mtk_iommu_data *data = mtk_iommu_get_m4u_data(); >>> struct mtk_iommu_domain *dom = to_mtk_domain(domain); >>> + bool is_in_gather = data->is_in_tlb_gather_add_page; >>> + size_t length = gather->end - gather->start; >>> unsigned long flags; >>> >>> - spin_lock_irqsave(&dom->pgtlock, flags); >>> - mtk_iommu_tlb_sync(mtk_iommu_get_m4u_data()); >>> - spin_unlock_irqrestore(&dom->pgtlock, flags); >>> + if (gather->start == ULONG_MAX) >>> + return; >>> + >>> + /* >>> + * Avoid acquire the lock when it's in gather_add_page since the lock >>> + * has already been held. >>> + */ >>> + if (!is_in_gather) >>> + spin_lock_irqsave(&dom->pgtlock, flags); >>> + >>> + mtk_iommu_tlb_add_flush_nosync(gather->start, length, gather->pgsize, >>> + false, data); >>> + mtk_iommu_tlb_sync(data); >>> + >>> + if (!is_in_gather) >>> + spin_unlock_irqrestore(&dom->pgtlock, flags); >>> } >>> >>> static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain, >>> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h >>> index fc0f16e..d29af1d 100644 >>> --- a/drivers/iommu/mtk_iommu.h >>> +++ b/drivers/iommu/mtk_iommu.h >>> @@ -58,6 +58,7 @@ struct mtk_iommu_data { >>> struct iommu_group *m4u_group; >>> bool enable_4GB; >>> bool tlb_flush_active; >>> + bool is_in_tlb_gather_add_page; >>> >>> struct iommu_device iommu; >>> const struct mtk_iommu_plat_data *plat_data; >>> > >