Messages in this thread Patch in this message | | | Date | Sat, 24 Feb 2024 10:41:36 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH 3/3] irqchip/gic-v3-its: Print the vPE table installed in redistributor |
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On Mon, 19 Feb 2024 18:58:08 +0000, Oliver Upton <oliver.upton@linux.dev> wrote: > > Hindsight is 20/20 of course, but the recent vPE table programming bug > could've been root caused a bit more quickly if we print the table > getting installed at every redistributor. > > Promote to pr_info() and add some additional context, such as the > provenance of the installed vPE table. > > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> > --- > drivers/irqchip/irq-gic-v3-its.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > index 63d1743f08cc..c3ef9665a2ad 100644 > --- a/drivers/irqchip/irq-gic-v3-its.c > +++ b/drivers/irqchip/irq-gic-v3-its.c > @@ -2835,7 +2835,8 @@ static int allocate_vpe_l1_table(void) > u64 val, gpsz, npg, pa; > unsigned int psz = SZ_64K; > unsigned int np, epp, esz; > - struct page *page; > + struct page *page = NULL; > + bool from_its = false; > > if (!gic_rdists->has_rvpeid) > return 0; > @@ -2865,8 +2866,10 @@ static int allocate_vpe_l1_table(void) > return -ENOMEM; > > val = inherit_vpe_l1_table_from_its(); > - if (val & GICR_VPROPBASER_4_1_VALID) > + if (val & GICR_VPROPBASER_4_1_VALID) { > + from_its = true; > goto out; > + }
nit: from_its = val & GICR_VPROPBASER_4_1_VALID; if (from_its) ...
> > /* First probe the page size */ > val = FIELD_PREP(GICR_VPROPBASER_4_1_PAGE_SIZE, GIC_PAGE_SIZE_64K); > @@ -2945,9 +2948,12 @@ static int allocate_vpe_l1_table(void) > gicr_write_vpropbaser(val, vlpi_base + GICR_VPROPBASER); > cpumask_set_cpu(smp_processor_id(), gic_data_rdist()->vpe_table_mask); > > - pr_debug("CPU%d: VPROPBASER = %llx %*pbl\n", > - smp_processor_id(), val, > - cpumask_pr_args(gic_data_rdist()->vpe_table_mask)); > + pr_info("CPU%d: Using %s vPE table @%llx (%s)\n", > + smp_processor_id(), > + (val & GICR_VPROPBASER_4_1_INDIRECT) ? "indirect" : "direct", > + val & GICR_VPROPBASER_4_1_ADDR, > + (page) ? "allocated" : > + ((from_its) ? "inherited from ITS" : "inherited from RD"));
From past experience, having the vpe_table_mask value displayed did help tracking VPE table affinity bugs.
This said, my problem with this patch is that we already have tons of these statement printed once per CPU/RD. This is really huge and accounts for a significant part of the boot time on large machines (64+ CPUs).
Before we add more of those, I'd really want to have a way to tone them down and only print them at runtime *if* required by the user. Kind of a dymanic debug, but driven from the command-line and present early enough.
What do you think?
M.
-- Without deviation from the norm, progress is not possible.
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