Re: [PATCH] platform/x86: intel_pmc_core: Do not ioremap RAM

From: Andy Shevchenko
Date: Fri Aug 16 2019 - 05:22:13 EST

On Fri, Aug 16, 2019 at 4:42 AM M. Vefa Bicakci <m.v.b@xxxxxxxxxx> 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