[kvm-devel] [PATCH]: Fake MSR_K7 performance counters

[Chris L. <cla...@re...>]

Attached is a patch that fixes a guest crash when booting older Linux kernels.
The problem stems from the fact that we are currently emulating
MSR_K7_EVNTSEL[0-3], but not emulating MSR_K7_PERFCTR[0-3].  Because of this,
setup_k7_watchdog() in the Linux kernel receives a GPF when it attempts to write
into MSR_K7_PERFCTR, which causes an OOPs.

The patch fixes it by just "fake" emulating the appropriate MSRs, throwing away
the data in the process.  This causes the NMI watchdog to not actually work, but
it's not such a big deal in a virtualized environment.

Tested by myself on a RHEL-4 guest, and Joerg Roedel on a Windows XP 64-bit guest.

Signed-off-by: Chris Lalancette <cla...@re...>