Debian "Wheezy" amd64 high RAM not visible.
Greetings to all who read this.
I've got a Lenovo B575e laptop. It has AMD E2-2000 CPU inside and a single stick of 4GB RAM. I've installed Debian "Wheezy" with amd64 architecture. The problem is that highest (the fourth, to be more accurate) gigabyte of the address space is not addressed to the RAM but to devices. I know there should be "memory remap"-like named option in the BIOS setup but it is a laptop you see. The laptop's BIOS setup does not allow many settings to be changed by the end user. So, the 'cpuid' command says (at the last line of its output): Code:
Maximum linear address: 48; maximum phys address 36 Code:
address sizes : 36 bits physical, 48 bits virtual And here is my E820 memory map: Code:
sergey@r2c3:~$ dmesg | grep -i e820 Code:
sergey@r2c3:~$ smem -R 4G -w Thanks in advance. Sorry for my broken English. |
I think you need to investigate amd iommu.
iommu is the amd way of handling high memory I had an early 64bit box and the boot would say things like "Hmmph! Found an iommu aperature at 4 Gigs - deleted it. it's clearly ridiculous. What were they smoking? Made a temporary one at 2 gigs. This is wasting good 64M ram on you." Subsequently the kernel was fixed, and you could specify iommu stuff with commands at boot time. don't know where things stand now. |
@business_kid
Before I made changes to my compilation configuration there were set options: CONFIG_AMD_IOMMU=y CONFIG_INTEL_IOMMU=y CONFIG_IRQ_REMP=y Now, I've set: CONFIG_AMD_IOMMU=y CONFIG_AMD_IOMMU_V2=m CONFIG_INTEL_IOMMU=y CONFIG_INTEL_IOMMU_DEFAULT_ON=y That still makes no effect. Currently, I'm reading Documentation/x86/x86_64/boot-options.txt, section IOMMU and I think I should put iommu option equal to force or noforce or setting amd_iommu to fullflush UPD: Interchanging between these boot options gives no effect with the new kernel. |
I would take the shourtcut of linux-laptop.net and look for guys running your hardware with a page up. Then see what worked for them.
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