On Fri, Jan 8, 2010 at 6:07 PM, Alexander Graf <ag...@suse.de> wrote: > > 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.
The frequency could be a parameter for the -cpu flag, like -cpu 970fx,frequency=1000000000.
