On Fri, Sep 22, 2023 at 03:21:17PM +0100, Robin Murphy wrote:
> On 22/09/2023 2:40 pm, Hector Martin wrote:
> > Commit a4fdd9762272 ("iommu: Use flush queue capability") hid the
> > IOMMU_DOMAIN_DMA_FQ domain type from domain allocation. A check was
> > introduced in iommu_dma_init_domain() to fall back if not supported, but
> > this check runs too late: by that point, devices have been attached to
> > the IOMMU, and the IOMMU driver might not expect FQ domains at
> > ops->attach_dev() time.
> >
> > Ensure that we immediately clamp FQ domains to plain DMA if not
> > supported by the driver at device attach time, not later.
> >
> > This regressed apple-dart in v6.5.
>
> Apologies, I missed that apple-dart was doing something unusual here.
> However, could we just fix that directly instead?
>
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index 2082081402d3..0b8927508427 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -671,8 +671,7 @@ static int apple_dart_attach_dev(struct iommu_domain
> *domain,
> return ret;
>
> switch (domain->type) {
> - case IOMMU_DOMAIN_DMA:
> - case IOMMU_DOMAIN_UNMANAGED:
> + default:
> ret = apple_dart_domain_add_streams(dart_domain, cfg);
> if (ret)
> return ret;
Yes, I much prefer this to the original patch please. Drivers should
not be testing DMA_FQ at all.
I already wrote a series to convert DART to domain_alloc_paging() that
fixes this inadvertantly.
Robin's suggestion is good for a temporary -rc fix.
Removing the switch is slightly more robust:
if (domain->type & domain->type & __IOMMU_DOMAIN_PAGING) {
[..]
return 0
}
if (domain->type == IOMMU_DOMAIN_BLOCKED) {
..
}
return -EOPNOTSUPP;
But not so worthwhile since I deleted all this anyhow...
I'll send out the dart series, it can't go to -rc, so a patch is still needed.
Thanks,
Jason
