linux-kernel - RE: [PATCH 2/4 RESEND] dma-mapping: Add wrapper function to set dma

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: <PH0PR21MB30252951848A6328E11385A4D7129@PH0PR21MB3025.namprd21.prod.outlook.com>
Date:   Thu, 17 Mar 2022 19:13:05 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Robin Murphy <robin.murphy@....com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: RE: [PATCH 2/4 RESEND] dma-mapping: Add wrapper function to set
 dma_coherent

From: Robin Murphy <robin.murphy@....com> Sent: Thursday, March 17, 2022 10:20 AM
> 
> On 2022-03-17 16:25, Michael Kelley via iommu wrote:
> > Add a wrapper function to set dma_coherent, avoiding the need for
> > complex #ifdef's when setting it in architecture independent code.
> 
> No. It might happen to work out on the architectures you're looking at,
> but if Hyper-V were ever to support, say, AArch32 VMs you might see the
> problem. arch_setup_dma_ops() is the tool for this job.
>

OK.   There's currently no vIOMMU in a Hyper-V guest, so presumably the
code would call arch_setup_dma_ops() with the dma_base, size, and iommu
parameters set to 0 and NULL.  This call can then be used in Patch 3 instead
of acpi_dma_configure(), and in the Patch 4 hv_dma_configure() function
as you suggested.  arch_setup_dma_ops() is not exported, so I'd need to
wrap it in a Hyper-V specific function in built-in code that is exported.

But at some point in the future if there's a vIOMMU in Hyper-V guests,
this approach will need some rework.

Does that make sense?  Thanks for your input and suggestions ...

Michael