lkml.org 
[lkml]   [2021]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping
On Wed, Jul 14, 2021 at 6:25 PM Joerg Roedel <joro@8bytes.org> wrote:
>
> On Tue, Jul 13, 2021 at 07:57:40PM -0400, Konrad Rzeszutek Wilk wrote:
> > The SWIOTLB does have support to do late initialization (xen-pcifront
> > does that for example - so if you add devices that can't do 64-bit it
> > will allocate something like 4MB).
>
> That sounds like a way to evaluate. I suggest to allocate the SWIOTLB
> memory at boot and when the IOMMUs are initialized we re-evaluate what
> we ended up with and free the SWIOTLB memory if its not needed.
>
> If that turns out to be wrong during runtime (e.g. because a device is
> switched to a passthrough default domain at runtime), we allocate a
> small aperture for this device like the above mentioned 4MB.

I am currently working on this but I found that 4MB is not enough,
16MB is the minimal size to make the device work.
How do I know the right SWIOTLB size for each device?

>
> (A boot option to always keep the aperture around might also be helpful
> for some setups)

OK, will also implement this in next iteration.

Kai-Heng

>
> Regards,
>
> Joerg

\
 
 \ /
  Last update: 2021-09-09 08:37    [W:0.082 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site