On Fri, Mar 12, 2010 at 07:09:41PM -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 There is a late mechanism to do kickoff the SWIOTLB. Perhaps the hot-add could use swiotlb_init_late and start up the SWIOTLB? > more efficiently (the current way is pretty dumb) I need to repost that. > > With that it would be relatively easy to do I think. > > -Andi > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- 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
