From: "Luis R. Rodriguez" <email@example.com> To: Toshi Kani <firstname.lastname@example.org> Cc: Prarit Bhargava <email@example.com>, Stuart Hayes <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, "H. Peter Anvin" <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Toshi Kani <email@example.com> Subject: Re: Fwd: [PATCH] x86: Use larger chunks in mtrr_cleanup Date: Thu, 3 Sep 2015 21:51:34 +0200 [thread overview] Message-ID: <20150903195134.GW8051@wotan.suse.de> (raw) In-Reply-To: <firstname.lastname@example.org> On Thu, Sep 03, 2015 at 01:22:42PM -0600, Toshi Kani wrote: > On Thu, 2015-09-03 at 20:40 +0200, Luis R. Rodriguez wrote: > > On Thu, Sep 03, 2015 at 02:10:14PM -0400, Prarit Bhargava wrote: > > > > > > > > > On 09/03/2015 01:59 PM, Luis R. Rodriguez wrote: > > > > On Thu, Sep 03, 2015 at 08:17:02AM -0400, Prarit Bhargava wrote: > > > > > > > > > > > > > > > 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). > > > > > > > > There were a few stragglers left on v4.2, I have transformed them in the > > > > latest development changes and those tranformations are now part of > > > > linux-next. If this is specific to a driver you may want to first ensure > > > > you backport the required patch that transforms the driver to use proper > > > > PAT interfaces, v4.2 should have most updates but there were still a few > > > > left. Just make sure your driver doesn't call mtrr_add() directly and if > > > > it doesn't then you should be OK. > > > > > > > > > In any case, Stuart -- could you try booting with > > > > > 'disable_mtrr_cleanup' as a kernel parameter? > > > > > > > > Indeed, please I'd like to hear back. Be sure to have the respective > > > > driver transformation in place, what driver are you using exactly? In > > > > the event that you argue this is still needed I'd like to know exaclty > > > > *why*, the comit log does not mention any of that at all. > > > > > > > > > > Well ... we are trying to also fix this in older kernels too, *cough* RHEL > > > *cough*, so that's where the patch comes from. If upstream is going to > > > deprecate/remove mtrr support so be it. > > > > Check linux-next, and Documentation/x86/mtrr.txt > > > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/Docume > > ntation/x86/mtrr.txt > > > > The platform use of MTRR is the only thing you should be concerned over but > > as noted returning MTRR_TYPE_INVALID should suffice if the OS does not make > > any driver use / modifications. > > The following sentence in the "mtrr.txt" is not correct. (Sorry I should have > caught it earlier.) mtrr_type_lookup() returns MTRR_TYPE_INVALID when MTRRs > are disabled, i.e. MTRRs are not set by neither firmware nor OS. Most of the > firmwares enable them, though. > > "If MTRRs are only set up by the platform firmware code though and the OS does > not make any specific MTRR mapping requests mtrr_type_lookup() should always > return MTRR_TYPE_INVALID." So this should be clarified to say -- that because platform firmware *may* make use of MTRRs, even if all OS drivers are no longer making use of MTRRs directly, we still need mtrr_type_lookup() to return the right type ? Luis
next prev parent reply other threads:[~2015-09-03 19:51 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <55E477DE.email@example.com> 2015-08-31 16:05 ` Stuart Hayes 2015-09-03 2:45 ` Luis R. Rodriguez 2015-09-03 12:17 ` Prarit Bhargava 2015-09-03 17:59 ` Luis R. Rodriguez 2015-09-03 18:10 ` Prarit Bhargava 2015-09-03 18:40 ` Luis R. Rodriguez 2015-09-03 19:22 ` Toshi Kani 2015-09-03 19:51 ` Luis R. Rodriguez [this message] 2015-09-03 21:31 ` Toshi Kani 2015-09-03 22:07 ` Luis R. Rodriguez 2015-09-03 22:25 ` Toshi Kani 2015-09-03 22:45 ` Luis R. Rodriguez 2015-09-03 23:21 ` Toshi Kani 2015-09-03 23:54 ` Luis R. Rodriguez 2015-09-04 0:48 ` Toshi Kani 2015-09-04 1:40 ` Luis R. Rodriguez 2015-09-04 14:56 ` Toshi Kani 2015-09-04 6:51 ` Jan Beulich 2015-09-14 14:46 ` Stuart Hayes 2015-11-05 19:14 ` Yinghai Lu 2015-11-05 19:43 ` Luis R. Rodriguez 2016-03-16 20:20 ` Luis R. Rodriguez 2016-03-29 17:07 ` Luis R. Rodriguez
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