[lkml]   [2007]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] quiet down swiotlb warnings
On Fri, 01 Jun 2007, Andi Kleen wrote:

> Rik van Riel <> 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?

The driver only calls pci_map_sg() once it's insured that all local
driver resources are available to submit an I/O to the hardware.

> > - 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.

Why? It's just another resource which is consumed -- the qla2xxx
driver is the final consumer before I/O is submitted out on the wire.
The mappings are held for the shorted time required -- as such, are
released as soon as the I/O completes.

> 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.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-06-01 20:19    [W:0.067 / U:17.064 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site