On 01/28, Andrey Wagin wrote: > > We use hardware breakpoints in CRIU and we found that sometimes we set > a break-point, but a process doesn't stop on it. reproduced, and this certainly looks like kvm bug to me. > The reproducer uses a different break-point address if it is executed > with arguments than when it executed without arguments. IOW, multiple processes running in parallel use the same debug register db0 but different address. And it seems that set_debugreg(address, 0) sometime doesn't work in the guest kernel. I think I verified the following: - debug registers look always correct as it seen by the guest. I used get_debugreg() to dump them after the task misses bp. - do_debug() was not called in this case. - finally, it seems that the host has the wrong value in db0 set by another process. I modified your test-case so that child2() calls child() when it detects the missed bp, and this does trigger do_debug/etc while it should not. Oleg. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
