On Mon, 2019-04-01 at 06:03:12 UTC, Michael Neuling wrote: > This adds a flag so that the DAWR can be enabled on P9 via: > echo Y > /sys/kernel/debug/powerpc/dawr_enable_dangerous > > The DAWR was previously force disabled on POWER9 in: > 9654153158 powerpc: Disable DAWR in the base POWER9 CPU features > Also see Documentation/powerpc/DAWR-POWER9.txt > > This is a dangerous setting, USE AT YOUR OWN RISK. > > Some users may not care about a bad user crashing their box > (ie. single user/desktop systems) and really want the DAWR. This > allows them to force enable DAWR. > > This flag can also be used to disable DAWR access. Once this is > cleared, all DAWR access should be cleared immediately and your > machine once again safe from crashing. > > Userspace may get confused by toggling this. If DAWR is force > enabled/disabled between getting the number of breakpoints (via > PTRACE_GETHWDBGINFO) and setting the breakpoint, userspace will get an > inconsistent view of what's available. Similarly for guests. > > For the DAWR to be enabled in a KVM guest, the DAWR needs to be force > enabled in the host AND the guest. For this reason, this won't work on > POWERVM as it doesn't allow the HCALL to work. Writes of 'Y' to the > dawr_enable_dangerous file will fail if the hypervisor doesn't support > writing the DAWR. > > To double check the DAWR is working, run this kernel selftest: > tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c > Any errors/failures/skips mean something is wrong. > > Signed-off-by: Michael Neuling <mi...@neuling.org>
Applied to powerpc topic/ppc-kvm, thanks. https://git.kernel.org/powerpc/c/c1fe190c06723322f2dfac31d3b982c5 cheers