On 26 November 2012 17:58, Ian Molton <ian.molton@xxxxxxxxxxxxxxx> wrote: > I'm looking at dirty page logging on KVM on ARM, which appears, at present > to be non-existent. Is anyone working on this, or willing to lend a hand? I've cc'd the kvmarm mailing list to give this a slightly wider airing. > I'm running KVM on an OMAP5, and my guest is a vexpress-a15 with PL-111 > framebuffer. > > running tcg mode, this works, however in KVM I was seeing (occasionally) one > frame of video. Yeah, not sure if anybody's tested video in a KVM guest. > Some debugging led me to the dirty_log code, and I discovered that qemu > makes a bad test for the return code from kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, > &d) in kvm_physical_sync_dirty_bitmap(), so the problem was going > unreported. > > Furthermore, I think the vexpress emulation was missing a call to > memory_region_set_log(vram, true, DIRTY_MEMORY_VGA); > for the vram region, which was preventing the host kernel knowing that dirty > page logging was required. (I think - Im not really very clear on the whole > qemu memory API, as AFAICT, its barely documented...) > > Anyhow, If I add the call to memory_region_set_log(), and if I ask the host > kernel to mark absolutely everything as dirty, it does in fact, work. > > Obviously this is a massive hack, but I'm not too sure where to go on from > here, so pointers would be nice. Presumably, I'm going to have to do some > prodding of the hosts page tables, but I'm not clear exactly what, as yet. -- PMM _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
