linux-kernel - Re: [PATCH] x86: trim ram need to check if mtrr is there v2

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Message-ID: <86802c440801250013p1a35b126l30fb7479b110e97d@mail.gmail.com>
Date:	Fri, 25 Jan 2008 00:13:20 -0800
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "Ingo Molnar" <mingo@...e.hu>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: trim ram need to check if mtrr is there v2

On Jan 24, 2008 11:43 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
> Yinghai Lu wrote:
> > [PATCH] x86: trim ram need to check if mtrr is there v2
> >
> >
> >>> Jeremy Fitzhardinge wrote:
> >>> When booting a current x86.git kernel under kvm, I get this:
> >>>
> >>> (qemu) Linux version 2.6.24-rc8 (jeremy@ezr) (gcc version 4.1.2 20070925
> >>> (Red Hat 4.1.2-33)) #1928 SMP PREEMPT Thu Jan 24 17:09:04 PST 2008
> >>> early_ioremap_init()
> >>> BIOS-provided physical RAM map:
> >>> BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
> >>> BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
> >>> BIOS-e820: 00000000000e8000 - 0000000000100000 (reserved)
> >>> BIOS-e820: 0000000000100000 - 000000001fff0000 (usable)
> >>> BIOS-e820: 000000001fff0000 - 0000000020000000 (ACPI data)
> >>> BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
> >>> console [earlyser0] enabled
> >>> 0MB HIGHMEM available.
> >>> 511MB LOWMEM available.
> >>> Scan SMP from c0000000 for 1024 bytes.
> >>> Scan SMP from c009fc00 for 1024 bytes.
> >>> Scan SMP from c00f0000 for 65536 bytes.
> >>> Scan SMP from c009fc00 for 1024 bytes.
> >>> ***************
> >>> **** WARNING: likely BIOS bug
> >>> **** MTRRs don't cover all of memory, trimmed 131056 pages
> >>> ***************
> >>>
> >> H. Peter Anvin wrote:
> >> Looks like the code doesn't check that the CPU *has* MTRRs...
> >>
> >
> > so check it mtrr is there, also check if mem less 4G and is AMD as early
> >
>
> Thanks, this gets me to usermode under kvm.

i think the is 0xffffffff to 0xffffffffUL make the difference.

the cpu mode in KVM/qemu may cpu_has_mtrr, but doesn't really have
return mtrr msr with correct value.

is_cpu(INTEL) already make sure we have mtrr_if got assigned and cpu_has_mtrr.

may need to fix qemu instead...

Can you try post /proc/mtrr for your guest in kvm/qemu?

Thanks

YH
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