On Tue, Aug 27, 2024 at 7:40 PM Cédric Le Goater <c...@kaod.org> wrote: > > Hello Clément, > > On 7/15/24 10:46, Clément Chigot wrote: > > The BookE decrementer stops at 0, meaning that it won't decremented > > towards "negative" values. > > However, the current logic is inverted: decr is updated solely when > > the resulting value would be negative. > > How did you hit the issue ? which machine ? I didn't see any error > when booting Linux 6.6.3 on mpc8544ds, e500mc, e5500 and e6500.
I hit this issue while running some version of VxWorks on a custom machine: p3041ds (description [1] and our local implementation [2]). So, I'm not that surprised you were not able to reproduce. > > Signed-off-by: Clément Chigot <chi...@adacore.com> > > Fixed: 8e0a5ac87800 ("hw/ppc: Avoid decrementer rounding errors") > > LGTM, > > Reviewed-by: Cédric Le Goater <c...@redhat.com> > > We have some automated tests with the ppce500 machine which it would be > interesting to extend to have a better coverage of booke. Thanks for the pointer, I'll see if I can extend them. > Thanks, > > C. > [1] https://www.nxp.com/design/design-center/software/qoriq-developer-resources/p3041-qoriq-development-system:P3041DS [2] https://github.com/AdaCore/qemu/blob/qemu-stable-9.0.0/hw/ppc/p3041ds.c > > > --- > > hw/ppc/ppc.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c > > index e6fa5580c0..9fc85c7de0 100644 > > --- a/hw/ppc/ppc.c > > +++ b/hw/ppc/ppc.c > > @@ -729,7 +729,9 @@ static inline int64_t __cpu_ppc_load_decr(CPUPPCState > > *env, int64_t now, > > int64_t decr; > > > > n = ns_to_tb(tb_env->decr_freq, now); > > - if (next > n && tb_env->flags & PPC_TIMER_BOOKE) { > > + > > + /* BookE timers stop when reaching 0. */ > > + if (next < n && tb_env->flags & PPC_TIMER_BOOKE) { > > decr = 0; > > } else { > > decr = next - n; > >