On Mon, 15 Mar 2010 20:51:40 -0400 Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: > 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? I guess that you are talking about swiotlb_late_init_with_default_size(), which IA64 uses. However, you can use swiotlb_late_init_with_default_size() only before we initialize devices. Making it work after initializing devices is not so easy, I think (that is, we need to change dma_ops). -- 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
