Re: [Patch v2 0/9] Fix AMD IOMMU faults in kdump kernel

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

On Fri, Nov 06, 2015 at 08:10:42PM +0800, Baoquan He wrote:
> This is v2 draft patch set. It mainly functions as the following steps:
> 
> 1. Checking if it's in kdump kernel and previously enabled
> 2. If yes do below operatons:
>     a. Do not disable amd iommu and do not touch dev tables before coping old dev tables
>     b. Copy dev table from old kernel and set the old domain id in amd_iommu_pd_alloc_bitmap
>     c. Copy irq tables from old kernel
>     d. Copy command buffer and event buffer
>     e. Don't call update_domain() to set domain->pt_root to dev entries before device driver initialization.
>     f. Reset the pre-enabled status in case IOMMU_DMA_OPS of state_next(). 
> 
> Existed problems:

"Existed" means here these problems are gone?

> 
> 1. It always prints the following message whenever do a flush:
> 
> 	"AMD-Vi: Completion-Wait loop timed out"
> 
> 2. Maybe there's someing wrong with the old irq remapping handling, the hard disk can't be brought up
> successfully. You can check the attached kdump kernel boot log with this patchset applied.

The reason is most likely that you didn't re-initialize the command
buffer before doing any flushes. The you see the above Completion-Wait
loop timeouts.


	Joerg