linux-kernel - Re: [PATCH 0/5] FlexRM support in VFIO platform

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: <CAALAos923XEO_oxHpqJN+XSG2MGvTc6evCf6pSg++0Qcj54vXQ@mail.gmail.com>
Date:   Wed, 19 Jul 2017 16:58:40 +0530
From:   Anup Patel <anup.patel@...adcom.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Will Deacon <will.deacon@....com>, Joerg Roedel <joro@...tes.org>,
        Baptiste Reynal <b.reynal@...tualopensystems.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Scott Branden <sbranden@...adcom.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        kvm@...r.kernel.org,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH 0/5] FlexRM support in VFIO platform

On Wed, Jul 19, 2017 at 4:55 PM, Robin Murphy <robin.murphy@....com> wrote:
> On 19/07/17 12:17, Anup Patel wrote:
>> On Wed, Jul 19, 2017 at 4:27 PM, Robin Murphy <robin.murphy@....com> wrote:
>>> On 19/07/17 10:33, Anup Patel wrote:
>>>> This patchset primarily adds Broadcom FlexRM reset module for
>>>> VFIO platform driver. We also have minor improvments in IOMMU
>>>> and VFIO driver to allow VFIO no-IOMMU mode access to FlexRM.
>>>
>>> I'm struggling to understand the IOMMU changes here - what's the
>>> FlexRM's hardware relationship with the IOMMU, and how is it different
>>> from any other device? Furthermore, if there *is* a relevant IOMMU
>>> present, why would no-IOMMU mode need to be involved at all?
>>
>> We want to have FlexRM device accessible from user-space
>> using VFIO platform with and without IOMMU.
>>
>> Currently, if IOMMU ops are available for platform bus then
>> I cannot access FlexRM device using VFIO no-IOMMU mode.
>
> So does the FlexRM hardware master through the SMMU or not? If it does,
> why do you need no-IOMMU mode? If it doesn't, then that's yet another
> reason to fix the real problem, which is the utterly broken notion of
> there being 'an IOMMU' on the platform 'bus', rather than papering over
> it in VFIO.
>

We are not trying to paper-over the issue. The ARM SMMU will
have limited number of SMRs so on a big SOC with large number
of DMA-capable devices we can run-out of SMRs if we try to
configure SMMU for all DMA-capable devices.

Regards,
Anup