On Tue, Jun 18, 2013 at 11:29:27AM -0400, Bandan Das wrote: > Gleb Natapov <gleb@xxxxxxxxxx> writes: > > > On Tue, Jun 18, 2013 at 04:05:08PM +0200, Paolo Bonzini wrote: > >> Il 05/06/2013 10:42, Gleb Natapov ha scritto: > >> >> > These patches add an emulated MSR_PLATFORM_INFO that kvm guests > >> >> > can read as described in section 14.3.2.4 of the Intel SDM. > >> >> > The relevant changes and details are in [2/2]; [1/2] makes vendor_intel > >> >> > generic. There are atleat two known applications that fail to run because > >> >> > of this MSR missing - Sandra and vTune. > >> > So I really want Intel opinion on this. Right now it is impossible to > >> > implement the MSR correctly in the face of migration (may be with tsc > >> > scaling it will be possible) and while it is unimplemented if application > >> > tries to use it it fails, but if we will implement it application will > >> > just produce incorrect result without any means for user to detect it. > >> > >> Jun, ping? (Perhaps Gleb you want to ask a more specific question though). > >> > >> I don't think this is much different from any other RDTSC usage in > >> applications (they will typically do their calibration manually, and do > >> it just once). I'm applying it to queue. > >> > > And we do not support application that uses RDTSC directly! If we could > > catch those it would be good from support point of view, so the way > > MSR_PLATFORM_INFO behaves now it better then proposed alternative. > > If support is the issue, can't we have a flag that disables this by > default and users who want to take the plunge (and be responsible > for the consequences) can enable it to read platform_info ? > We have it already :) ignore_msrs. If it is set unimplemented MSRs will not inject #GP, but return zero value instead. Zero it as incorrect as anything else in the case of migration. -- Gleb. -- 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
