Re: [Qemu-devel] [PATCH] target/ppc/excp_helper: Take BQL before calling cpu_interrupt()

["Alex Bennée" <alex.bennee@linaro.org>]

Thomas Huth <thuth@redhat.com> writes:

> Since the introduction of MTTCG, using the msgsnd instruction
> abort()s if being called without holding the BQL. So let's protect
> that part of the code now with qemu_mutex_lock_iothread().
>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1694998
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

p.s. I was checking the ppc code for other CPU_FOREACH patterns and I
noticed the tlb_flush calls could probably use the tlb_flush_all_cpus
API instead of manually looping themselves. You should also double check
the semantics to make sure none of them need to use the _synced variant
and a cpu_exit if the flush needs to complete w.r.t the originating CPU.

> ---
>  target/ppc/excp_helper.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 9cb2123..3a9f086 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -17,6 +17,7 @@
>   * License along with this library; if not, see <http://www.gnu.org/licenses/>.
>   */
>  #include "qemu/osdep.h"
> +#include "qemu/main-loop.h"
>  #include "cpu.h"
>  #include "exec/helper-proto.h"
>  #include "exec/exec-all.h"
> @@ -1132,6 +1133,7 @@ void helper_msgsnd(target_ulong rb)
>          return;
>      }
>
> +    qemu_mutex_lock_iothread();
>      CPU_FOREACH(cs) {
>          PowerPCCPU *cpu = POWERPC_CPU(cs);
>          CPUPPCState *cenv = &cpu->env;
> @@ -1141,5 +1143,6 @@ void helper_msgsnd(target_ulong rb)
>              cpu_interrupt(cs, CPU_INTERRUPT_HARD);
>          }
>      }
> +    qemu_mutex_unlock_iothread();
>  }
>  #endif


--
Alex Bennée