On 08.01.2010, at 19:04, Blue Swirl wrote: > On Fri, Jan 8, 2010 at 5:43 PM, Alexander Graf <ag...@suse.de> wrote: >> Our guest systems need to know by how much the timebase increases every >> second, >> so there usually is a "timebase-frequency" property in the cpu leaf of the >> device tree. >> >> This property is missing in OpenBIOS, as is the "clock-frequency" property >> that >> tells the guest how fast the CPU is. FWIW that one is only used for >> /proc/cpuinfo though. >> >> With qemu, Linux's fallback timebase speed and qemu's internal timebase speed >> match up. With KVM, that is no longer true. The guest is running at the same >> timebase speed as the host. >> >> This leads to massive timing problems. On my test machine, a "sleep 2" takes >> about 14 seconds with KVM enabled. >> >> This patch exports the timebase and clock frequencies to OpenBIOS, so it can >> then put them into the device tree. I'll push the OpenBIOS change with the >> NewWorld patch set, once that's either been reviewed or applied. > > IIRC copying the host CPU frequency to guest was rejected earlier for x86.
Well IIRC x86 Linux tries to find out the cpu frequency itself. PPC Linux doesn't - it completely relies on entries in the device tree. Alex
