On Tue Dec 19, 2023 at 9:47 PM AEST, Thomas Huth wrote:
> On 16/12/2023 14.42, Nicholas Piggin wrote:
> > Storing certain values in some registers can cause asynchronous
> > interrupts that can crash the test case, for example decrementer
> > or PMU interrupts.
> >
> > Change the msleep to mdelay which does not enable MSR[EE] and so
> > avoids the problem. This allows removing some of the SPR special
> > casing.
> >
> > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> > ---
> > powerpc/sprs.c | 14 ++------------
> > 1 file changed, 2 insertions(+), 12 deletions(-)
> >
> > diff --git a/powerpc/sprs.c b/powerpc/sprs.c
> > index 01041912..313698e0 100644
> > --- a/powerpc/sprs.c
> > +++ b/powerpc/sprs.c
> > @@ -481,12 +481,7 @@ static void set_sprs(uint64_t val)
> > continue;
> > if (sprs[i].type & SPR_HARNESS)
> > continue;
> > - if (!strcmp(sprs[i].name, "MMCR0")) {
> > - /* XXX: could use a comment or better abstraction! */
> > - __mtspr(i, (val & 0xfffffffffbab3fffULL) | 0xfa0b2070);
> > - } else {
> > - __mtspr(i, val);
> > - }
> > + __mtspr(i, val);
> > }
> > }
> >
> > @@ -536,12 +531,7 @@ int main(int argc, char **argv)
> > if (pause) {
> > migrate_once();
> > } else {
> > - msleep(2000);
> > -
> > - /* Taking a dec updates SRR0, SRR1, SPRG1, so don't fail. */
> > - sprs[26].type |= SPR_ASYNC;
> > - sprs[27].type |= SPR_ASYNC;
> > - sprs[273].type |= SPR_ASYNC;
> > + mdelay(2000);
> > }
>
> IIRC I used the H_CEDE stuff here on purpose to increase the possibility
> that the guest gets rescheduled onto another CPU core on the host, and thus
> that it uncovers sprs that are not saved and restored on the host more
> easily. So I'd rather keep the msleep() here.
Ah. Not a bad idea. I'll see about making it deal with H_CEDE
instead.
I wonder if there would be a way to stress host CPU migration
in the test harness. Instead of waiting for QEMU to exit, the
script could run taskset in a loop to bounce it around.
Conceptually easy, probably fiddly to wire things up nicely.
I may try to take a look at adding that... but after this
series so it doesn't get any bigger :/
Thanks,
Nick
