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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 22 Oct 2021 21:54:40 +0200
Message-ID: <CAK8P3a35adaG9OzWWFSvjJcQo+hEnEJuLCL-8je-m+78JfjWxQ@mail.gmail.com>
Subject: Re: [GIT PULL] soc/fsl drivers changes for fix(v5.15)
To:     Li Yang <leoyang.li@nxp.com>
Cc:     arm-soc <arm@kernel.org>, SoC Team <soc@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Ioana Ciornei <ioana.ciornei@nxp.com>,
        Diana Craciun <diana.craciun@nxp.com>
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On Fri, Oct 22, 2021 at 3:00 AM Li Yang <leoyang.li@nxp.com> wrote:
> ----------------------------------------------------------------
> NXP/FSL SoC driver fixes for v5.15

> - fix qbman alignment error in the virtualization context

This patch looks very suspicious to me, I don't think it's generally safe to
use memcpy_toio() on a normal pointer, as the __iomem tokens may
be in a separate address range, even though this currently works
on arm64. Adding the  (__iomem void *) cast without a comment that
explains why it's added seems similarly wrong, and finally the
changeset text does not seem to match what the code does:

According to the text, the pointer is to a virtual address mapped as
"device memory" (i.e. PROT_DEVICE_nGnRE or PROT_DEVICE_nGnRnE),
but the code suggests it's actually write-combining normal
(PROT_NORMAL_NC).

I don't see any discussion of this patch on the mailing list either, so
please resend the pull request without this patch, while we try to figure
out what the driver should actually be doing here.

       Arnd