On Fri, Dec 21, 2012 at 06:42:47PM -0800, Eric W. Biederman wrote: > Konrad Rzeszutek Wilk <konrad.w...@oracle.com> writes: > > > On Mon, Dec 17, 2012 at 11:15:56PM -0800, Yinghai Lu wrote: > >> So use could disable swiotlb from command line, even swiotlb support > >> is compiled in. Just like we have intel_iommu=on and intel_iommu=off. > > > > You really need to spell out why this is useful. > > YH why can't we safely autodetect that the swiotlb is unusable when > there is no memory below 4G free?
I am not sure what 'YH' stands for (Yeah?). However we could turn SWIOTLB off altogether if it cannot allocate _some_ memory. It could try first 64MB, then 32MB, lastly 16MB. And if all that fails - print a nice warning and continue on. Later in the late initialization phase, when pci_swiotlb_late_init is called - it can then figure out whether 'iommu' has been set and it iself was never able to allocate. At that point it can try the dynamic allocation (swiotlb_late_init_with_default_size) ... and if that fails give up and panic. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
