Re: [kvm-devel] [PATCH]: Fix MSR_K7_EVNTSEL{0,3} for SVM

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

Avi Kivity wrote:
> Now it uses %rsi instead of %esi, and any junk in the upper bits will 
> cause the ja to be taken.
> 
> We need to get a reduced testcase to the gcc folks, this is a serious 
> bug.  Any changes in the code to work around this would be fragile.
> 

Avi,
    I've now filed a bug in the upstream gcc database:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36040

And I came up with a reduced test case, available here:

http://people.redhat.com/clalance/rsi-test-case.tar.bz2

If I compile the code in the above and look at the disassembly, it shows the
problem; however, I can't reproduce the bug by actually running the code.  I
suspect the %rsi register is always 0 when we start in this userland code, so I
never run into the bogus ja, but I just thought I'd mention it.

Chris Lalancette