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SubjectRe: oops/warning report for the week of November 26, 2008
Arjan van de Ven wrote:
> On Thu, 27 Nov 2008 21:18:36 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
>
>> * Arjan van de Ven <arjan@linux.intel.com> wrote:
>>
>>> Ingo Molnar wrote:
>>>> * Arjan van de Ven <arjan@linux.intel.com> wrote:
>>>>
>>>>> Rank 8: mtrr_trim_uncached_memory (warning)
>>>>> Reported 227 times (619 total reports)
>>>>> There is a high number of machines where our MTRR checks
>>>>> trigger. I suspect we are too picky in accepting the MTRR
>>>>> configuration.
>>>> the warning here means: "the BIOS messed up but we fixed it up for
>>>> you just fine".
>>> I don't believe that right now. we see so many of these, including
>>> many "there's no MTRRs at all", that I am seriously suspecting that
>>> our code is just incorrect somehow and triggering too much.
>> well we looked at existing reports and Linux was right to fix them
>> up. Show us one that is incorrect, then we can fix it up.
>>
>> the "no MTRR's" are vmware/(also qemu?) guests not implementing a
>> full CPU emulation.
>
> ... and it's still our fault in part, since we don't even check to see
> if a cpu claims to support MTRR before complaining about it...
>
> easy to fix though:
>
> From 7e987ae541c41ce908b414fee9d8e2fd2099a083 Mon Sep 17 00:00:00 2001
> From: Arjan van de Ven <arjan@linux.intel.com>
> Date: Thu, 27 Nov 2008 12:25:47 -0800
> Subject: [PATCH] x86: make sure the CPU advertizes MTRR support before complaining about the lack thereoff...
>
> We complain loudly if a CPU does not have MTRR support... but we don't check if the CPU
> exposes MTRR support in the CPUID flags first. While this might not fix all of the
> broken virtualization systems out there, it will at least fix those that properly don't
> advertize things they don't support.
>
> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
> ---
> arch/x86/kernel/cpu/mtrr/main.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index 1159e26..0044e61 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -1567,6 +1567,8 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
> * Make sure we only trim uncachable memory on machines that
> * support the Intel MTRR architecture:
> */
> + if (!cpu_has_mtrr)
> + return 0;

that is not needed, we already check that in mtrr_bp_init before this function is called, and it will assign mtrr_if

and
#define is_cpu(vnd) (mtrr_if && mtrr_if->vendor == X86_VENDOR_##vnd)

will make it sure mtrr is there.

ps: here INTEL mean any cpu has same interface like intel cpu's

YH

> if (!is_cpu(INTEL) || disable_mtrr_trim)
> return 0;
> rdmsr(MTRRdefType_MSR, def, dummy);



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