On 05/04/2018 12:41 PM, Michael Ellerman wrote: > Cédric Le Goater <c...@kaod.org> writes: > >> The kexec_state KEXEC_STATE_IRQS_OFF barrier is reached by all >> secondary CPUs before the kexec_cpu_down() operation is called on >> secondaries. This can raise conflicts and provoque errors in the XIVE >> hcalls when XIVE is shutdowned with H_INT_RESET on the primary CPU. >> >> To synchronize the kexec_cpu_down() operations and make sure the >> secondaries have completed their task before the primary starts doing >> the same, let's move the primary kexec_cpu_down() after the >> KEXEC_STATE_REAL_MODE barrier. > > This sounds reasonable, I'm sure you've tested it. I'm just a bit > worried that it could potentially break on other platforms because it > changes the sequence of operations.
yes. We are adding a last barrier to be exact making the full sequence a little slower. > Looking we only have kexec_cpu_down() implemented for pseries, powernv, > ps3 and 85xx. > > We can easily test the first two. > ps3 doesn't do much so hopefully that's > safe. > > mpc85xx_smp_kexec_cpu_down() does very little on 32-bit, and on 64-bit > it seems to already wait for at least one other CPU to get into > KEXEC_STATE_REAL_MODE, so that's probably safe too. > > So I guess I'm OK to merge this, and we'll fix any fallout. It would be > good for the change log to call out the change though, and that we think > it's a sensible change for all platforms. OK. Thanks, C. > cheers > >> Signed-off-by: Cédric Le Goater <c...@kaod.org> >> --- >> arch/powerpc/kernel/machine_kexec_64.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/arch/powerpc/kernel/machine_kexec_64.c >> b/arch/powerpc/kernel/machine_kexec_64.c >> index 49d34d7271e7..212ecb8e829c 100644 >> --- a/arch/powerpc/kernel/machine_kexec_64.c >> +++ b/arch/powerpc/kernel/machine_kexec_64.c >> @@ -230,16 +230,16 @@ static void kexec_prepare_cpus(void) >> /* we are sure every CPU has IRQs off at this point */ >> kexec_all_irq_disabled = 1; >> >> - /* after we tell the others to go down */ >> - if (ppc_md.kexec_cpu_down) >> - ppc_md.kexec_cpu_down(0, 0); >> - >> /* >> * Before removing MMU mappings make sure all CPUs have entered real >> * mode: >> */ >> kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE); >> >> + /* after we tell the others to go down */ >> + if (ppc_md.kexec_cpu_down) >> + ppc_md.kexec_cpu_down(0, 0); >> + >> put_cpu(); >> } >> >> -- >> 2.13.6
