Re: [PATCH 12/12] xen/mtrr: Add mtrr_if support for Xen mtrr

Stefano Stabellini
2010-09-28T14:01:12Z

On Tue, 28 Sep 2010, Ingo Molnar wrote:
>
> * stefano.stabellini@eu.citrix.com <stefano.stabellini@eu.citrix.com> wrote:
>
> > From: Stephen Tweedie <sct@redhat.com>
> >
> > Add a Xen mtrr type, and reorganise mtrr initialisation slightly to
> > allow the mtrr driver to set up num_var_ranges (Xen needs to do this by
> > querying the hypervisor itself.)
> >
> > [ Impact: add basic MTRR support ]
> >
> > Signed-off-by: Stephen Tweedie <sct@redhat.com>
> > Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > ---
> > arch/x86/kernel/cpu/mtrr/Makefile | 2 +-
> > arch/x86/kernel/cpu/mtrr/main.c | 3 +
> > arch/x86/kernel/cpu/mtrr/mtrr.h | 7 ++
> > arch/x86/kernel/cpu/mtrr/xen.c | 110 +++++++++++++++++++++++++++++++++++++
> > 4 files changed, 121 insertions(+), 1 deletions(-)
> > create mode 100644 arch/x86/kernel/cpu/mtrr/xen.c
>
> Still NAK, for the very same reasons as we NAK-ed it the previous time:
> /proc/mtrr is a problematic and complicated legacy interface that should
> die. Any modern X server will do the right thing via PAT.
>

Sorry I should have read the original thread more carefully: I didn't
realize this patch had been NAK-ed.

However it is not a problem because we can easily disable MTRRs from Xen
and with no cpu_has_mtrr the kernel would still boot fine on Xen.
Also I think we do have PAT support nowadays but I'll let Jeremy comment
on that.

> Also, please get the Ack of at least one x86 maintainer for x86 patches.
>

I'll repost the series without the last two patches, so there won't be
any x86 changes at all :)

Many thanks for your quick feedback,

Stefano