linux-kernel - Re: [PATCH v3 6/7] iommu/mediatek: Gather iova in iommu

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Message-ID: <20210118165833.GA17722@willie-the-truck>
Date:   Mon, 18 Jan 2021 16:58:34 +0000
From:   Will Deacon <will@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Tomasz Figa <tfiga@...gle.com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, youlin.pei@...iatek.com,
        Nicolas Boichat <drinkcat@...omium.org>, anan.sun@...iatek.com,
        chao.hao@...iatek.com, Greg Kroah-Hartman <gregkh@...gle.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 6/7] iommu/mediatek: Gather iova in iommu_unmap to
 achieve tlb sync once

On Mon, Jan 18, 2021 at 04:35:22PM +0000, Robin Murphy wrote:
> On 2020-12-16 10:36, Yong Wu wrote:
> > In current iommu_unmap, this code is:
> > 
> > 	iommu_iotlb_gather_init(&iotlb_gather);
> > 	ret = __iommu_unmap(domain, iova, size, &iotlb_gather);
> > 	iommu_iotlb_sync(domain, &iotlb_gather);
> > 
> > We could gather the whole iova range in __iommu_unmap, and then do tlb
> > synchronization in the iommu_iotlb_sync.
> > 
> > This patch implement this, Gather the range in mtk_iommu_unmap.
> > then iommu_iotlb_sync call tlb synchronization for the gathered iova range.
> > we don't call iommu_iotlb_gather_add_page since our tlb synchronization
> > could be regardless of granule size.
> > 
> > In this way, gather->start is impossible ULONG_MAX, remove the checking.
> > 
> > This patch aims to do tlb synchronization *once* in the iommu_unmap.
> 
> Assuming the update to patch #4 simply results in "unsigned long end = iova
> + size - 1;" here,
> 
> Reviewed-by: Robin Murphy <robin.murphy@....com>

There's a v4 here:

https://lore.kernel.org/r/20210107122909.16317-1-yong.wu@mediatek.com

Will