john cooper 91c9c3eda4 KVM: x86: handle guest access to BBL_CR_CTL3 MSR ... A correction to Intel cpu model CPUID data (patch queued) caused winxp to BSOD when booted with a Penryn model. This was traced to the CPUID "model" field correction from 6 -> 23 (as is proper for a Penryn class of cpu). Only in this case does the problem surface. The cause for this failure is winxp accessing the BBL_CR_CTL3 MSR which is unsupported by current kvm, appears to be a legacy MSR not fully characterized yet existing in current silicon, and is apparently carried forward in MSR space to accommodate vintage code as here. It is not yet conclusive whether this MSR implements any of its legacy functionality or is just an ornamental dud for compatibility. While I found no silicon version specific documentation link to this MSR, a general description exists in Intel's developer's reference which agrees with the functional behavior of other bootloader/kernel code I've examined accessing BBL_CR_CTL3. Regrettably winxp appears to be setting bit #19 called out as "reserved" in the above document. So to minimally accommodate this MSR, kvm msr get will provide the equivalent mock data and kvm msr write will simply toss the guest passed data without interpretation. While this treatment of BBL_CR_CTL3 addresses the immediate problem, the approach may be modified pending clarification from Intel. Signed-off-by: john cooper <john.cooper@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>		2011-03-17 13:08:27 -03:00
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asm	KVM: x86: handle guest access to BBL_CR_CTL3 MSR	2011-03-17 13:08:27 -03:00