Re: [PATCH] quiet down swiotlb warnings

Andi Kleen
2007-06-01T18:05:26Z

Rik van Riel <riel@redhat.com> writes:

> It turns out that the qla2xxx driver sometimes fills up the iotlb
> on purpose and throttles itself when pci_map_sg() fails. In the
> case of a driver that expects and handles pci_map_sg() failures,
> we should not spam the user's console with swiotlb full messages.

Why does it do that? Could we supply a better interface
for whatever it is trying to do here?

> */
> - printk(KERN_ERR "DMA: Out of SW-IOMMU space for %zu bytes at "
> - "device %s\n", size, dev ? dev->bus_id : "?");
> + if (++warnings < 5)
> + printk(KERN_ERR "DMA: Out of SW-IOMMU space for %zu bytes at "
> + "device %s\n", size, dev ? dev->bus_id : "?");

Bad idea imho. swiotlb mappings should always lead to printk by default
because it is pretty dangerous.

One possible solution for this I could think of would be to define a
new pci_map_sg_couldfail() or similar that doesn't warn and use a weak
fallback just calling pci_map_sg on other IOMMU implementations.

-Andi