Re: [PATCH] iommu/amd: Don't put completion-wait semaphore on stack

[Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

* Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> wrote:

> From: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
> 
> The semaphore used by the AMD IOMMU to signal command
> completion lived on the stack until now, which was safe as
> the driver busy-waited on the semaphore with IRQs disabled,
> so the stack can't go away under the driver.
> 
> But the recently introduced vmap-based stacks break this as
> the physical address of the semaphore can't be determinded
> easily anymore. The driver used the __pa() macro, but that
> only works in the direct-mapping. The result were
> Completion-Wait timeout errors seen by the IOMMU driver,
> breaking system boot.
> 
> Since putting the semaphore on the stack is bad design
> anyway, move the semaphore into 'struct amd_iommu'. It is
> protected by the per-iommu lock and now in the direct
> mapping again. This fixes the Completion-Wait timeout errors
> and makes AMD IOMMU systems boot again with vmap-based
> stacks enabled.
> 
> Reported-by: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
> Signed-off-by: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>
> ---
>  drivers/iommu/amd_iommu.c       | 14 ++++++++------
>  drivers/iommu/amd_iommu_types.h |  2 ++
>  2 files changed, 10 insertions(+), 6 deletions(-)

Cool, thanks! I'll put this into tip:x86/asm which has the virtually mapped stack 
patches - ok?

Thanks,

	Ingo