On Fri, 31 Jul 2020 at 16:17, Nicolas Saenz Julienne <[email protected]> wrote: > > Hi Amit, > > On Wed, 2020-07-29 at 17:52 +0530, Amit Pundir wrote: > > On Wed, 29 Jul 2020 at 16:15, Nicolas Saenz Julienne > > <[email protected]> wrote: > > > On Tue, 2020-07-28 at 17:30 +0200, Christoph Hellwig wrote: > > > > On Tue, Jul 28, 2020 at 06:18:41PM +0530, Amit Pundir wrote: > > > > > > Oh well, this leaves me confused again. It looks like your setup > > > > > > really needs a CMA in zone normal for the dma or dma32 pool. > > > > > > > > > > Anything I should look up in the downstream kernel/dts? > > > > > > > > I don't have a good idea right now. Nicolas, can you think of something > > > > else? > > > > > > To summarise, the device is: > > > - Using the dma-direct code path. > > > - Requesting ZONE_DMA memory to then fail when provided memory falls in > > > ZONE_DMA. Actually, the only acceptable memory comes from CMA, which is > > > located topmost of the 4GB boundary. > > > > > > My wild guess is that we may be abusing an iommu identity mapping setup by > > > firmware. > > > > > > That said, what would be helpful to me is to find out the troublesome > > > device. > > > Amit, could you try adding this patch along with Christoph's modified > > > series > > > (so the board boots). Ultimately DMA atomic allocations are not that > > > common, so > > > we should get only a few hits: > > > > Hi, still not hitting dma_alloc_from_pool(). > > Sorry I insisted, but not hitting the atomic path makes the issue even harder > to understand.
No worries. I was more concerned about not following the instructions correctly. Thank you for looking into this issue. > > > I hit the following direct alloc path only once, at starting: > > > > dma_alloc_coherent () > > -> dma_alloc_attrs() > > -> dma_is_direct() -> dma_direct_alloc() > > -> dma_direct_alloc_pages() > > -> dma_should_alloc_from_pool() #returns FALSE from here > > > > After that I'm hitting following iommu dma alloc path all the time: > > > > dma_alloc_coherent() > > -> dma_alloc_attrs() > > -> (ops->alloc) -> iommu_dma_alloc() > > -> iommu_dma_alloc_remap() #always returns from here > > > > So dma_alloc_from_pool() is not getting called at all in either of the > > above cases. > > Ok, so lets see who's doing what and with what constraints: Here is the relevant dmesg log: https://pastebin.ubuntu.com/p/dh3pPnxS2v/ Regards, Amit Pundir > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 4959f5df21bd..d28b3e4b91d3 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -594,6 +594,9 @@ static void *iommu_dma_alloc_remap(struct device *dev, > size_t size, > dma_addr_t iova; > void *vaddr; > > + dev_info(dev, "%s, bus_dma_limit %llx, dma_mask %llx, > coherent_dma_mask %llx, in irq %lu, size %lu, gfp %x, attrs %lx\n", > + __func__, dev->bus_dma_limit, *dev->dma_mask, > dev->coherent_dma_mask, in_interrupt(), size, gfp, attrs); > + > *dma_handle = DMA_MAPPING_ERROR; > > if (unlikely(iommu_dma_deferred_attach(dev, domain))) > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index bb0041e99659..e5474e709e7b 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -160,6 +160,9 @@ void *dma_direct_alloc_pages(struct device *dev, size_t > size, > > size = PAGE_ALIGN(size); > > + dev_info(dev, "%s, bus_dma_limit %llx, dma_mask %llx, > coherent_dma_mask %llx, in irq %lu, size %lu, gfp %x, attrs %lx\n", > + __func__, dev->bus_dma_limit, *dev->dma_mask, > dev->coherent_dma_mask, in_interrupt(), size, gfp, attrs); > + > if (dma_should_alloc_from_pool(dev, gfp, attrs)) { > ret = dma_alloc_from_pool(dev, size, &page, gfp); > if (!ret) > _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
