Oleg Nesterov wrote: > On 12/18, Roland McGrath wrote: >>> Please find the trivial test-case below. It hangs, because >>> PTRACE_SINGLESTEP doesn't trigger the trap. >> 2.6.33-rc1 x86-64 works for me with either -m64 or -m32 version of that test. >> >>> (not sure this matters, but I did the testing under kvm) >> Apparently it does. You should hack some printks into do_debug() and see >> how kvm is differing from real hardware. (Actually you can probably do >> this with a notifier added by a module, not that you are shy about >> recompiling!) >> >> Probably kvm's emulation of the hardware behavior wrt the DR6 bits is not >> sufficiently faithful. Conceivably, kvm is being consistent with some >> older hardware and we have encoded assumptions that only newer hardware >> meets. But I'd guess it's just a plain kvm bug. > > OK, thanks. > > Hmm. Now I see how wrong I was when I said this code is "obviously wrong" ;) > > I'll add the debugging printk's and report the output. Sorry for delay, > can't do this today.
Can't reproduce, runs fine here with with 2.6.33-rc1 as both host&guest and qemu-kvm latest git. Host uses kvm-intel. Can you specify your setup in more details? Which host kernel did you use, which qemu-kvm version? Are you on AMD or Intel? Any specific guest kernel config switch that may influence this? Jan
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