Hi Robin,
> From: Robin Murphy, Sent: Friday, June 14, 2019 6:55 PM
>
> On 13/06/2019 11:20, Yoshihiro Shimoda wrote:
<snip>
> > +bool blk_queue_can_use_iommu_merging(struct request_queue *q,
> > + struct device *dev)
> > +{
> > + struct iommu_domain *domain;
> > +
> > + /*
> > + * If the device DMA is translated by an IOMMU, we can assume
> > + * the device can merge the segments.
> > + */
> > + if (!device_iommu_mapped(dev))
>
> Careful here - I think this validates the comment I made when this
> function was introduced, in that that name doesn't necesarily mean what
> it sounds like it might mean - "iommu_mapped" was as close as we managed
> to get to a convenient shorthand for "performs DMA through an
> IOMMU-API-enabled IOMMU". Specifically, it does not imply that
> translation is *currently* active; if you boot with "iommu=pt" or
> equivalent this will still return true even though the device will be
> using direct/SWIOTLB DMA ops without any IOMMU translation.
Thank you for your comments. I understood the mean of "iommu_mapped" and
this patch's condition causes a problem on iommu=pt.
So, I'll add and additional condition like
"domain->type == IOMMU_DOMAIN_DMA" to check whether the translation is
currently active on the domain or not.
Best regards,
Yoshihiro Shimoda
