linux-kernel - Re: [PATCH] Replace ioremap

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Message-ID: <20231127185611.GA27813@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date:   Mon, 27 Nov 2023 10:56:11 -0800
From:   Nischala Yelchuri <niyelchu@...ux.microsoft.com>
To:     Wei Liu <wei.liu@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-fbdev@...r.kernel.org, kys@...rosoft.com,
        haiyangz@...rosoft.com, decui@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, drawat.floss@...il.com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, deller@....de,
        mhklinux@...look.com, mhkelley@...look.com,
        singhabhinav9051571833@...il.com, niyelchu@...rosoft.com
Subject: Re: [PATCH] Replace ioremap_cache() with memremap()

Wei, this is one of the Hyper-V code improvement tasks that Michael Kelley identified.
Using memremap() is the right thing to do here. Abhinav Singh (cc'ed) also
tried to fix this earlier as there are sparse warnings with ioremap_cache().

On Sun, Nov 12, 2023 at 11:12:33PM +0000, Wei Liu wrote:
> On Wed, Nov 01, 2023 at 09:01:48AM -0700, Nischala Yelchuri wrote:
> > Current Hyper-V code for CoCo VMs uses ioremap_cache() to map normal memory as decrypted.
> > ioremap_cache() is ideally used to map I/O device memory when it has the characteristics
> > of normal memory. It should not be used to map normal memory as the returned pointer
> > has the __iomem attribute.
> 
> Do you find any real world issues with the current code? How do you
> discover these issues?
> 
> Thanks,
> Wei.