Avi Kivity wrote: > On 12/03/2009 08:21 PM, Jan Kiszka wrote: >> Merge 8e2c5ec2f6 forgot to restore some qemu-kvm-specific hooks in >> cpu_post_load. mp_state was readded later on, but tsc was missing, >> breaking the guest timing after resume. Also, reset of halt was dropped >> which is obviously required for in-kernel irqchip. >> > > Applied, thanks. > >> BTW, this patch just made me realize that the TSC MSR belongs to the >> list states that should not be written back unconditionally. Upstream >> does this currently, qemu-kvm not (at the price one more kvm-specific >> hook into generic code). > > Yet another reminder why we don't rewrite, only refactor. Which also has it's downsides like slow merging progress with quite a few subtle merge regressions on qemu-kvm side... > >> Unlike the other states we discussed, this one >> is not "fixable" in the kernel. So I tend to think there is a real need >> for my write-back scope abstraction - which would also be able to handle >> the other states cleanly, both in upstream and here. >> > > Yes. Gleb suggested treating mpstate/nmi as part of the APIC state > (which makes sense), which would work, as APIC state is not > automatically written back. But the tsc msr would need special treatment. (just realized that I forgot to answer him) While this would make sense for mpstate, NMIs are not coupled to the APICs. The APIC just happens to be one source for them (though a common one). So if there is no in-kernel APIC state, there would never be a write-back of the NMI state, which is bad. That said, I think we should hurry to add some mask to the new KVM_SET_VCPU_EVENTS (for 2.6.33) in order to skip nmi_pending and sipi_vector, giving us maximum flexibility how to address the issue. Will send a patch later. Jan
Attachment:
signature.asc
Description: OpenPGP digital signature
