[gentoo-user] Re: Another X11 problem

[Ian Zimmerman <itz@primate.net>]

On 2016-08-26 16:09, Corbin Bird wrote:

> >> I don't remember if you specified your appended command-line kernel
> >> parameters ( lilo / grub / grub2 ). I have an AMD Phenom II x4 980. The
> >> parameters have a major effect on the video ( i.e. AGP / IOMMU usage ).

> Try setting up the IOMMU. ( Stabilize memory setup / management )
> 
> The IOMMU is really a modified "AGP bridge" built into the CPU.
> 
> Typical dmesg output :
> [    0.000000] AGP: No AGP bridge found
> 
> If you don't create a "reserved for the AGP Aperature" memory block or 
> setup the IOMMU, the kernel will setup 64Mg of memory and reserve it for 
> "e820 -> AGP Aperature". If the IOMMU is not setup, it will 
> automatically use ALL of the "AGP Aperature Reserved" memory.
> 
> The added kernel parameter for ( AGP / IOMMU on x86_64 ) : 
> iommu=memaper[=1],noaperture
> 
> This sets up 64Mg for the IOMMU, and tells it "do not touch 'reserved 
> for the AGP Aperature' memory".
> ( Software IO TLB is now preferred / automatic on 4.1.xx kernels. )
> 
> Typical dmesg output :
> [    0.636904] AMD-Vi: Found IOMMU at 0000:00:00.2 cap 0x40
> [    0.637060] AMD-Vi: Interrupt remapping enabled
> [    0.644282] AMD-Vi: Lazy IO/TLB flushing enabled
> [    0.717543] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
> [    0.717700] software IO TLB [mem 0xb9ee4000-0xbdee4000] (64MB) mapped 
> at [ffff8800b9ee4000-ffff8800bdee3fff]
> 
> KMS enabled X drivers need this setup on ( Fam10h / Fam15h ) CPUs.

Some of the dmesg output on my system:

root@matica ~ # dmesg | fgrep -e AGP -e IOMMU -e TLB
[    0.000000] AGP: No AGP bridge found
[    0.000000] AGP: Checking aperture...
[    0.000000] AGP: No AGP bridge found
[    0.000000] AGP: Node 0: aperture [bus addr 0xa4000000-0xa5ffffff] (32MB)
[    0.000000] AGP: Your BIOS doesn't leave an aperture memory hole
[    0.000000] AGP: Please enable the IOMMU option in the BIOS setup
[    0.000000] AGP: This costs you 64MB of RAM
[    0.000000] AGP: Mapping aperture over RAM [mem 0xa4000000-0xa7ffffff] (65536KB)
[    0.005699] Last level iTLB entries: 4KB 512, 2MB 16, 4MB 8
[    0.005700] Last level dTLB entries: 4KB 512, 2MB 128, 4MB 64, 1GB 0
[    0.802036] PCI-DMA: Disabling AGP.
[    0.802111] PCI-DMA: using GART IOMMU.
[    0.802113] PCI-DMA: Reserving 64MB of IOMMU area in the AGP aperture

Do your recommendations still hold?

FWIW my BIOS setup has no option even remotely mentioning IOMMU, so I
don't know what the kernel is trying to tell me there.

This video is integrated with my motherboard (Gigabyte GA-880GM) and it
is not an external card plugged into a slot.

The kernel module is radeon and I'm pretty sure kernel modesetting is
the default.

Lastly, I never had this problem with 3.x kernels and the same hardware
(on Debian, and I think the last I used was 3.12, but I could be wrong
by a couple).

Thanks for trying to help!

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