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From:   Nadav Amit <nadav.amit@gmail.com>
Message-Id: <FB4E11A5-84D4-4DAF-889E-FAA1BCD2E66F@gmail.com>
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Subject: =?utf-8?Q?Re=3A_A_problem_of_Intel_IOMMU_hardware_=EF=BC=9F?=
Date:   Tue, 16 Mar 2021 22:46:00 -0700
In-Reply-To: <670baaf8-4ff8-4e84-4be3-030b95ab5a5e@huawei.com>
Cc:     David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>, will@kernel.org,
        alex.williamson@redhat.com, chenjiashang@huawei.com,
        iommu@lists.linux-foundation.org,
        "Gonglei (Arei)" <arei.gonglei@huawei.com>,
        LKML <linux-kernel@vger.kernel.org>
To:     "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@huawei.com>
References: <670baaf8-4ff8-4e84-4be3-030b95ab5a5e@huawei.com>
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> On Mar 16, 2021, at 8:16 PM, Longpeng (Mike, Cloud Infrastructure =
Service Product Dept.) <longpeng2@huawei.com> wrote:
>=20
> Hi guys,
>=20
> We find the Intel iommu cache (i.e. iotlb) maybe works wrong in a =
special
> situation, it would cause DMA fails or get wrong data.
>=20
> The reproducer (based on Alex's vfio testsuite[1]) is in attachment, =
it can
> reproduce the problem with high probability (~50%).

I saw Lu replied, and he is much more knowledgable than I am (I was just
intrigued by your email).

However, if I were you I would try also to remove some =
=E2=80=9Coptimizations=E2=80=9D to
look for the root-cause (e.g., use domain specific invalidations instead
of page-specific).

The first thing that comes to my mind is the invalidation hint (ih) in
iommu_flush_iotlb_psi(). I would remove it to see whether you get the
failure without it.


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