Hi Andi, On Fri, 2010-03-12 at 19:09 -0800, Andi Kleen wrote: > , Alok Kataria wrote: > > Hi Alok, > > > Hi, > > > > Looking at the current code swiotlb is initialized for 64bit kernels > > only when the max_pfn value is greater than 4G (MAX_DMA32_PFN value). > > So in cases when the initial memory is less than 4GB the kernel boots > > without enabling swiotlb, when we hotadd memory to such a kernel and go > > beyond the 4G limit, swiotlb is still disabled. As a result when any > > 32bit devices start using this newly added memory beyond 4G, the kernel > > starts spitting error messages like below or in some cases it causes > > kernel panics. > > Yes seems like a real problem. > > > > > 1. Enable swiotlb for all 64bit kernels which have memory hot-add > > support. > > I don't think that's a good idea. It would enable it everywhere on > distributions which compile with hotadd. Need (2) > > > 2. Instead of checking the max_pfn value in pci_swiotlb_detect, check > > for max_hotpluggable_pfn (or some such) value. Though I don't see such a > > value readily available. I could parse the SRAT and get hotplug memory > > information but that will make swiotlb detection logic a little too > > complex. A quick look around srat_xx.c files and the acpi_memhotplug > > module didn't find any useful API that could be used directly either. > > So was wondering if any of you are aware of an easy way to get such > > information ? > > I have a patchkit to revamp the SRAT parsing to store the hotadd information > more efficiently (the current way is pretty dumb) I need to repost that. Can you please send me any pointers to that patch series. Also am just curious to know about any merge plans for that patchkit. Thanks, Alok > > With that it would be relatively easy to do I think. > > -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
