Messages in this thread Patch in this message | | | Date | Tue, 12 Jun 2012 12:39:54 +0200 | From | Borislav Petkov <> | Subject | Re: CPU MTRRs and linux kernel |
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On Tue, Jun 12, 2012 at 02:37:40AM -0700, Mahmood Naderan wrote: > Hi everybody, > Abour rhis warnning in boot log: > > WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 61952MB of RAM > > > I > searched a lot however didn't find a clear solution. Does AMD new > processors (62XX) have problems with new kernels or old kernels?? > Mine is: > > Linux n1 2.6.32-24-server #39-Ubuntu SMP Wed Jul 28 06:21:40 UTC 2010 x86_64 GNU/Linux > > Should I upgrade?
Yes, fix is below and it got backported to -stable AFAICT but obviously the ubuntus don't have it in the kernel you cite above.
commit 3fdbf004c1706480a7c7fac3c9d836fa6df20d7d Author: Andreas Herrmann <andreas.herrmann3@amd.com> Date: Thu Sep 30 14:32:35 2010 +0200
x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] exists on all future AMD CPUs
Instead of adapting the CPU family check in amd_special_default_mtrr() for each new CPU family assume that all new AMD CPUs support the necessary bits in SYS_CFG MSR.
Tom2Enabled is architectural (defined in APM Vol.2). Tom2ForceMemTypeWB is defined in all BKDGs starting with K8 NPT. In pre K8-NPT BKDG this bit is reserved (read as zero).
W/o this adaption Linux would unnecessarily complain about bad MTRR settings on every new AMD CPU family, e.g.
[ 0.000000] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 4863MB of RAM. Cc: stable@kernel.org # .32.x, .35.x Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com> LKML-Reference: <20100930123235.GB20545@loge.amd.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c index c5f59d071425..ac140c7be396 100644 --- a/arch/x86/kernel/cpu/mtrr/cleanup.c +++ b/arch/x86/kernel/cpu/mtrr/cleanup.c @@ -827,7 +827,7 @@ int __init amd_special_default_mtrr(void) if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) return 0; - if (boot_cpu_data.x86 < 0xf || boot_cpu_data.x86 > 0x11) + if (boot_cpu_data.x86 < 0xf) return 0; /* In case some hypervisor doesn't pass SYSCFG through: */ if (rdmsr_safe(MSR_K8_SYSCFG, &l, &h) < 0) -- Regards/Gruss, Boris. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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