Re: [gentoo-user] Re: Issues with AMD_IOMMU

[Corbin Bird]

On 05/16/2017 01:34 AM, Adam Carter wrote:
> Answer #1 :
>
>
>     Asrock, Extreme6, 990FX, UEFI, AMD FX-9590
>     Gigabyte, GA-MA790FX-UD5P, 790FX, BIOS, AMD PhenomII x4 980
>
>
> Hi Corbin,
>
> I noticed i didnt have x2apic enabled on my 990FX / FX-8350 system, so
> i've rebuilt/rebooted etc, but;
>
> # zgrep X2APIC /proc/config.gz
> CONFIG_X86_X2APIC=y
> # dmesg | grep -i x2apic
> #
>
> On my skylake box
> # dmesg | grep -i x2apic
> [    0.044148] DMAR-IR: Queued invalidation will be enabled to support
> x2apic and Intr-remapping.
> [    0.045802] DMAR-IR: Enabled IRQ remapping in x2apic mode
> [    0.045908] x2apic enabled
> [    0.046011] Switched APIC routing to cluster x2apic.
>
> What x2apic messages do you get on your 990FX / FX-9590 system?


Interesting kernel parameter for you to try :
( from '/usr/src/linux/Documentation/kernel-parameters.txt' )

x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
			default x2apic cluster mode on platforms
			supporting x2apic.

With that switch I have not been getting any output in 'dmesg' about
this at all.

Question :
Do you have this enabled in your kernel ...
>   [ ]   Support for Intel IOMMU using DMA Remapping Devices


Corbin