From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3 3/6] iommu: add ARM short descriptor page table allocator.
Date: Wed, 16 Sep 2015 13:55:35 +0100 [thread overview]
Message-ID: <20150916125535.GI28771@arm.com> (raw)
In-Reply-To: <1442233500.19588.35.camel@mhfsdcap03>
Hello Yong,
On Mon, Sep 14, 2015 at 01:25:00PM +0100, Yong Wu wrote:
> On Tue, 2015-07-21 at 18:11 +0100, Will Deacon wrote:
> > > + ret = _arm_short_map(data, iova, paddr, pgdprot, pteprot, large);
> > > +
> > > + tlb->tlb_add_flush(iova, size, true, data->iop.cookie);
> > > + tlb->tlb_sync(data->iop.cookie);
> >
> > In _arm_short_map, it looks like you can only go from invalid -> valid,
> > so why do you need to flush the TLB here?
>
> Hi Will,
> Here is about flush-tlb after map iova, I have deleted it in v4
> following this suggestion. But We meet a problem about it.
Ok.
> Take a example with JPEG. the test steps is:
> a).JPEG HW decode a picture with the source iova,like 0xfd780000.
> b).JPEG HW decode done, It will unmap the iova(write 0 in pagetable and
> flush tlb).
> c).JPEG HW decode the second picture, whose source iova is also
> 0xfd780000.
> Then our HW maybe fail due to it will auto prefetch, It may prefecth
> between the step b) and c). then the HW may fetch the pagetable content
> which has been unmapped in step b). then the HW will get the iova's
> physical address is 0, It will translation fault!
Oh no! So-called "negative caching" is certainly prohibited by the ARM
architecture, but if you've built it then we can probably work around it
as an additional quirk. I assume the prefetcher stops prefetching when
it sees an invalid descriptor?
> So I think our HW need flush-tlb after map iova. Could we add a
> QUIRK like "IO_PGTABLE_QUIRK_AUTO_PREFETCH_ENABLE" for it?
> If it's not allowed, we will have to add this in our internal function
> mtk_iommu_map of mtk_iommu.c.
Actually, this type of quirk is ringing bells with me (I think another
IOMMU needed something similar in the past), so maybe just add
IO_PGTABLE_QUIRK_TLBI_ON_MAP?
Will
next prev parent reply other threads:[~2015-09-16 12:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 9:04 [PATCH v3 0/6] MT8173 IOMMU SUPPORT Yong Wu
2015-07-16 9:04 ` [PATCH v3 1/6] dt-bindings: iommu: Add binding for mediatek IOMMU Yong Wu
2015-07-16 9:04 ` [PATCH v3 2/6] dt-bindings: mediatek: Add smi dts binding Yong Wu
2015-07-16 9:04 ` [PATCH v3 3/6] iommu: add ARM short descriptor page table allocator Yong Wu
2015-07-21 17:11 ` Will Deacon
2015-07-24 5:24 ` Yong Wu
2015-07-24 16:53 ` Will Deacon
2015-07-27 4:21 ` Yong Wu
2015-07-27 14:05 ` Robin Murphy
2015-07-27 14:11 ` Will Deacon
2015-07-28 5:08 ` Yong Wu
2015-07-28 11:00 ` Will Deacon
2015-07-28 13:37 ` Yong Wu
2015-07-28 13:47 ` Will Deacon
[not found] ` <1438329337.25925.147.camel@mhfsdcap03>
2015-07-31 11:32 ` Will Deacon
2015-09-14 12:25 ` Yong Wu
2015-09-16 12:55 ` Will Deacon [this message]
2015-09-17 2:38 ` Yong Wu
2015-07-16 9:04 ` [PATCH v3 4/6] memory: mediatek: Add SMI driver Yong Wu
2015-07-16 9:04 ` [PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver Yong Wu
2015-07-21 14:59 ` Will Deacon
2015-07-24 5:43 ` Yong Wu
2015-07-24 16:55 ` Will Deacon
2015-07-27 4:24 ` Yong Wu
2015-07-27 15:48 ` Will Deacon
2015-07-27 13:23 ` Robin Murphy
2015-07-27 15:31 ` Russell King - ARM Linux
2015-07-27 15:49 ` Robin Murphy
2015-07-29 5:41 ` Yong Wu
2015-07-29 10:31 ` Will Deacon
2015-07-29 6:32 ` Yong Wu
2015-07-16 9:04 ` [PATCH v3 6/6] dts: mt8173: Add iommu/smi nodes for mt8173 Yong Wu
2015-07-23 14:40 ` Daniel Kurtz
2015-07-29 7:29 ` Yong Wu
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