On 06/22/10 11:31, Peter Zijlstra wrote: > On Tue, 2010-06-22 at 17:29 +0800, Zhang, Yanmin wrote: >> On Tue, 2010-06-22 at 10:00 +0200, Jes Sorensen wrote: >>> On 06/22/10 09:55, Peter Zijlstra wrote: >>>> On Tue, 2010-06-22 at 15:47 +0800, Zhang, Yanmin wrote: >>>>> Besides the para virt perf interface, I'm also considering the direct exposition >>>>> of PMU hardware to guest os. >>>> >>>> NAK NAK NAK NAK, we've been over that, its not going to happen, full >>>> stop! >>>> >>>> Use MSR read/write traps and host perf to emulate the hardware. In some >>>> cases we could allow the reads without trap but that's a later >>>> optimization. >>> >>> I believe whats meant here is a PMU compatible interface which is >>> partially emulated. Not a handover of the PMU. >> Right. We need capture all write to PMU MSR and allows guest os to read MSR directly. > > That latter is not possible, only in a subset of cases can you allow > that read. Avi's suggestion of using virtual MSRs makes a ton of sense for this though, and it makes it possible to switch direct access on/off for the cases where direct access is possible, and go emulated when it isn't. Cheers, Jes -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
