Re: [Qemu-devel] [RFC PATCH] target-arm/psci.c: wake up sleeping CPUs (MTTCG)

[Andrew Jones]

On Wed, Jun 24, 2015 at 08:12:52PM +0100, Peter Maydell wrote:
> On 24 June 2015 at 18:18, Alex Bennée <address@hidden> wrote:
> >
> > Paolo Bonzini <address@hidden> writes:
> >
> >> On 24/06/2015 17:34, Alex Bennée wrote:
> >>> Testing with Alexander's bare metal syncronisation tests fails in MTTCG
> >>> leaving one CPU spinning forever waiting for the second CPU to wake up.
> >>> We simply need to poke the halt_cond once we have processed the PSCI
> >>> power on call.
> >>>
> >>> Tested-by: Alex Bennée <address@hidden>
> >>> CC: Alexander Spyridakis <address@hidden>
> >>>
> >>> ---
> >>> TODO
> >>>   - exactly how does the vexpress wake up it's sleeping CPUs?
> >>> ---
> >>>  target-arm/psci.c | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>> diff --git a/target-arm/psci.c b/target-arm/psci.c
> >>> index d8fafab..661ff28 100644
> >>> --- a/target-arm/psci.c
> >>> +++ b/target-arm/psci.c
> >>> @@ -196,6 +196,8 @@ void arm_handle_psci_call(ARMCPU *cpu)
> >>>          }
> >>>          target_cpu_class->set_pc(target_cpu_state, entry);
> >>>
> >>> +        qemu_cond_signal(target_cpu_state->halt_cond);
> >>
> >> That's called qemu_cpu_kick(target_cpu_state). :)  The patch should be
> >> acceptable now upstream, I think.
> >
> > Oh so this might well fail in KVM too?
> 
> In KVM we won't use target-arm/psci.c because PSCI calls
> are handled in the kernel.
>

It's also not valid to use Alexander's test on KVM, as the test
framework doesn't enable the mmu, and thus {ldr,str}ex won't work
as expected.

I guess I need to do a better job at advertising/documenting
kvm-unit-tests/arm, as that framework would suit this test just
fine. I've attached a patch porting the test over to k-u-t[1].
After applying the patch, do

./configure --arch=arm64 --cross-prefix=aarch64-linux-gnu-
OR
./configure --arch=arm --cross-prefix=arm-linux-gnu-

make

arm/run arm/vos-spinlock-test.flat -smp 4 # non-atomic locks
OR
arm/run arm/vos-spinlock-test.flat -smp 4 -append atomic # atomic locks

Thanks,
drew

[1] git://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git

vos-spinlock-test.patch
Description: Text document