Hello, These three patches (one against host kernel, one against kvm.git, one against kvm-userland.git) forces KVM to map all RAM mapped in the virtualized e820 map provided to the guest with gfn = hfn. In turn it's now possible to give direct hardware access to the guest, all DMA will work fine on the virtualized guest ram.
The bios has to be updated to alter the end of the first ram slot in the virtualized e820 map. This is unfixable as the address hardcoded in the current bios is higher than what's marked as ram in my hardware e820 map. The only exception where gfn != hfn for ranges included in the virtualized e820 map is for the magic bios page at host physical address zero (bytes from 0 to 4096). All linux versions will definitely never attempt to dma on such a page. If all OS are like linux there will be no problem and pci passthrough will work regardless of the guest OS without requiring any paravirtualization, nor VT-d. This only implements the memory management side, the logic to map mmio regions into kvm address space will require further changes. The limit of the reserved ram is around 1G and it has to be set at compile time, so the guest will run with no more than 1G of ram (it's fairly easy to extend it to 2G though). You can't run more than one guest with -reserved-ram at once or they'll be overwriting themself. You need access to /dev/mem on the userland side, and CAP_ADMIN on the kernel side to run this. I choosed an approach to require the minimal number of changes given this is a short term approach due the lack of hardware features in lots of cpus out there. This is how the memory layout looks like when live guest runs (physical start set to 512M and kvm -m 300). 7f108d429000-7f108d42b000 rw-p 7f108d429000 00:00 0 7f108d42b000-7f108d4ba000 rw-s 00000000 00:0e 275 /dev/mem 7f108d4ba000-7f108d52a000 rw-p 7f108d4ba000 00:00 0 7f108d52a000-7f10a002a000 rw-s 00100000 00:0e 275 /dev/mem 7f10a002a000-7f10a142e000 rw-p 7f10a002a000 00:00 0 PID TTY STAT TIME MAJFL TRS DRS RSS %MEM COMMAND 5522 ? SLl 4:06 1 1568 427067 33144 7.0 bin/x86_64/kvm/bin/qemu-system-x86_64 -hda tmp/vir RSS isn't including the reserved ram of course. ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
