Messages in this thread | | | From | Kai-Heng Feng <> | Date | Thu, 9 Sep 2021 14:32:55 +0800 | Subject | Re: [PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping |
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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
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