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: Mon, 14 Oct 2019 15:21:13 +0100 Message-ID: References: <1571035101-4213-1-git-send-email-yong.wu@mediatek.com> <1571035101-4213-4-git-send-email-yong.wu@mediatek.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1571035101-4213-4-git-send-email-yong.wu@mediatek.com> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Yong Wu , Matthias Brugger , Joerg Roedel , Will Deacon Cc: 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 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. 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; >