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Subject: Re: [PATCH v12 2/5] iommu: Enhance IOMMU default DMA mode build
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To:     Lu Baolu <baolu.lu@linux.intel.com>, <joro@8bytes.org>,
        <will@kernel.org>, <dwmw2@infradead.org>, <robin.murphy@arm.com>
CC:     <linux-kernel@vger.kernel.org>, <iommu@lists.linux-foundation.org>,
        <linuxarm@huawei.com>, <thunder.leizhen@huawei.com>,
        <chenxiang66@hisilicon.com>
References: <1623414043-40745-1-git-send-email-john.garry@huawei.com>
 <1623414043-40745-3-git-send-email-john.garry@huawei.com>
 <a4c85f00-918b-5952-7585-8e1110ac5195@linux.intel.com>
From:   John Garry <john.garry@huawei.com>
Message-ID: <953e1210-c88f-3e50-fbb9-cc559923829e@huawei.com>
Date:   Mon, 14 Jun 2021 09:11:14 +0100
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On 12/06/2021 02:21, Lu Baolu wrote:
> On 2021/6/11 20:20, John Garry wrote:
>> +config IOMMU_DEFAULT_LAZY
>> +    bool "lazy"
>> +    help
>> +      Support lazy mode, where for every IOMMU DMA unmap operation, the
>> +      flush operation of IOTLB and the free operation of IOVA are 
>> deferred.
>> +      They are only guaranteed to be done before the related IOVA 
>> will be
>> +      reused.
>> +
>> +      The isolation provided in this mode is not as secure as STRICT 
>> mode,
>> +      such that a vulnerable time window may be created between the DMA
>> +      unmap and the mapping finally being torn down in the IOMMU, 
>> where the
>> +      device can still access the system memory. However this mode may
> 
> " ... and the mappings cached in the IOMMU IOTLB or device TLB finally
> being invalidated, where the device probably can still access the memory
> which has already been unmapped by the device driver."

ok, I can try to incorporate some of this wording.

As for this:

On 12/06/2021 03:12, Lu Baolu wrote:
 > On 2021/6/11 20:20, John Garry wrote:
 >> +choice
 >> +    prompt "IOMMU default DMA mode"
 >
 > This is not explicit.
 >
 > How about
 >
 > "IOMMU DMA default cache invalidation policy"
 >
 > ?
 >

OK, but I'd rather use IOTLB, as that better matches the relevant 
iommu.c API name (iommu_ops.flush_iotlb_all).

Thanks,
john