linux-kernel - Re: [PATCH] platform/x86: intel_pmc

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Date:   Fri, 16 Aug 2019 12:21:58 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "M. Vefa Bicakci" <m.v.b@...box.com>
Cc:     Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>
Subject: Re: [PATCH] platform/x86: intel_pmc_core: Do not ioremap RAM

On Fri, Aug 16, 2019 at 4:42 AM M. Vefa Bicakci <m.v.b@...box.com> wrote:
>
> On a Xen-based PVH virtual machine with more than 4 GiB of RAM,
> intel_pmc_core fails initialization with the following warning message
> from the kernel, indicating that the driver is attempting to ioremap
> RAM:
>
>   ------------[ cut here ]------------
>   ioremap on RAM at 0x00000000fe000000 - 0x00000000fe001fff

> This issue appears to manifest itself because of the following fallback
> mechanism in the driver:
>
>         if (lpit_read_residency_count_address(&slp_s0_addr))
>                 pmcdev->base_addr = PMC_BASE_ADDR_DEFAULT;
>
> The validity of address PMC_BASE_ADDR_DEFAULT (i.e., 0xFE000000) is not
> verified by the driver, which is what this patch introduces. With this
> patch, if address PMC_BASE_ADDR_DEFAULT is in RAM, then the driver will
> not attempt to ioremap the aforementioned address.

Thank you for the patch.
Is there anything preventing us to use memremap() in such case?

-- 
With Best Regards,
Andy Shevchenko