linux-kernel - Re: [PATCH] x86: fixed mtrr change WP to WB

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Date:	Tue, 6 May 2008 11:34:39 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: fixed mtrr change WP to WB

On Tue, May 6, 2008 at 11:31 AM, H. Peter Anvin <hpa@...or.com> wrote:
> Yinghai Lu wrote:
>
> >
> > >
> > >  If the mptable should be modified, it should be copied to kernel memory
> and
> > > modified there.  Modifying it in-place is both unsafe and, in general,
> > > simply will not work.
> > >
> >
> > but
> >
> >         * 1) Scan the bottom 1K for a signature
> >         * 2) Scan the top 1K of base RAM
> >         * 3) Scan the 64K of bios
> >         */
> >        if (smp_scan_config(0x0, 0x400, reserve) ||
> >            smp_scan_config(639 * 0x400, 0x400, reserve) ||
> >            smp_scan_config(0xF0000, 0x10000, reserve))
> >                return;
> >
> > and all these areas are reserved already.
> >
> > wonder if we could only modify mpf->mpf_physptr to point to another
> > mpc and reuse mpf?
> >
> >
>
>  Obviously, if you have already modified a table, you should save a pointer
> to it, and not rely on the kernel scanning later.

that modified mptable is for second kernel that is kexeced.

YH
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