linux-kernel - Re: [PATCH v12 2/5] iommu: Enhance IOMMU default DMA mode build options

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <953e1210-c88f-3e50-fbb9-cc559923829e@huawei.com>
Date:   Mon, 14 Jun 2021 09:11:14 +0100
From:   John Garry <john.garry@...wei.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>, <joro@...tes.org>,
        <will@...nel.org>, <dwmw2@...radead.org>, <robin.murphy@....com>
CC:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>,
        <linuxarm@...wei.com>, <thunder.leizhen@...wei.com>,
        <chenxiang66@...ilicon.com>
Subject: Re: [PATCH v12 2/5] iommu: Enhance IOMMU default DMA mode build
 options

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