On 2011-04-29 17:38, Alex Williamson wrote: > On Fri, 2011-04-29 at 17:29 +0200, Jan Kiszka wrote: >> On 2011-04-29 17:06, Michael S. Tsirkin wrote: >>> On Thu, Apr 28, 2011 at 09:15:23PM -0600, Alex Williamson wrote: >>>> When we're trying to get a newly registered phys memory client updated >>>> with the current page mappings, we end up passing the region offset >>>> (a ram_addr_t) as the start address rather than the actual guest >>>> physical memory address (target_phys_addr_t). If your guest has less >>>> than 3.5G of memory, these are coincidentally the same thing. If >> >> I think this broke even with < 3.5G as phys_offset also encodes the >> memory type while region_offset does not. So everything became RAMthis >> way, no MMIO was announced. >> >>>> there's more, the region offset for the memory above 4G starts over >>>> at 0, so the set_memory client will overwrite it's lower memory entries. >>>> >>>> Instead, keep track of the guest phsyical address as we're walking the >>>> tables and pass that to the set_memory client. >>>> >>>> Signed-off-by: Alex Williamson <alex.william...@redhat.com> >>> >>> Acked-by: Michael S. Tsirkin <m...@redhat.com> >>> >>> Given all this, can yo tell how much time does >>> it take to hotplug a device with, say, a 40G RAM guest? >> >> Why not collect pages of identical types and report them as one chunk >> once the type changes? > > Good idea, I'll see if I can code that up. I don't have a terribly > large system to test with, but with an 8G guest, it's surprisingly not > very noticeable. For vfio, I intend to only have one memory client, so > adding additional devices won't have to rescan everything. The memory > overhead of keeping the list that the memory client creates is probably > also low enough that it isn't worthwhile to tear it all down if all the > devices are removed. Thanks,
What other clients register late? Do the need to know to whole memory layout? This full page table walk is likely a latency killer as it happens under global lock. Ugly. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
