Re: Fwd: [PATCH] x86: Use larger chunks in mtrr_cleanup

From: Prarit Bhargava
Date: Thu Sep 03 2015 - 08:17:28 EST

On 09/02/2015 10:45 PM, Luis R. Rodriguez wrote:
> On Mon, Aug 31, 2015 at 11:05:33AM -0500, Stuart Hayes wrote:
>> Increase the range of chunk sizes tried in mtrr_cleanup() so it is able
>> to map large memory configs into MTRRs.
>> Currently, mtrr_cleanup() will fail with large memory configurations,
>> because it limits chunk_size to 2GB, which means that each MTRR can only
>> cover 2GB of memory. With a memory size of, say, 256GB, and ten variable
>> MTRRs (such as some recent Intel CPUs have), it is not possible to set up
>> the MTRRs to cover all of memory.
> Linux drivers no longer use MTRR so why is the cleanup needed, ie, what would
> happen if the cleanup is just skipped in your case ?

The infiniband & video drivers still use MTRR (or at least it was my
understanding that they do). In any case, Stuart -- could you try booting with
'disable_mtrr_cleanup' as a kernel parameter?

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