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 hostguest
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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