linux-kernel - Re: [PATCH 2/3] ARM/keystone: move the DMA offset handling under ifdef CONFIG_ARM

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: <20200911111551.GG1551@shell.armlinux.org.uk>
Date:   Fri, 11 Sep 2020 12:15:51 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sh@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/3] ARM/keystone: move the DMA offset handling under
 ifdef CONFIG_ARM_LPAE

On Thu, Sep 10, 2020 at 07:40:37AM +0200, Christoph Hellwig wrote:
> The DMA offset notifier can only be used if PHYS_OFFSET is at least
> KEYSTONE_HIGH_PHYS_START, which can't be represented by a 32-bit
> phys_addr_t.  Currently the code compiles fine despite that, a pending
> change to the DMA offset handling would create a compiler warning for
> this case.  Add an ifdef to not compile the code except for LPAE
> configs.

However, to have use of the high physical offset, LPAE needs to be
enabled, which ensures that phys_addr_t is 64-bit.

I believe that DMA is non-coherent on this platform unless the high
physical address is used. Or something like that.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!