We go through quite a bit of trouble to make sure we pick up any
preallocated LPI tables on the redistributors, as enabling LPIs is a
one-way switch. There is no such restriction for vLPIs, and for GICv4.1
we expect to allocate a new vPE table at boot.
This works as intended when initializing an ITS, however when setting up
a redistributor in its_cpu_init_lpis() the early return for preallocated
RD tables skips straight past GICv4 setup. This all comes to a head when
trying to kexec into a new kernel, as the new kernel silently fails to
set up GICv4, leading to a complete loss of SGIs and LPIs for KVM VMs
(ouch).
Slap a band-aid on the problem by ensuring its_cpu_init_lpis() always
initializes GICv4 on the way out, even if the other RD tables were
preallocated.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 6479450f72c1 ("irqchip/gic-v4: Fix occasional VLPI drop")
Reported-by: George Cherian <gcherian@xxxxxxxxxxx>
Co-developed-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
I debated a bit on the fixes tag between the blamed commit and commit
5e5168461c22 ("irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER)
allocation"), although it would appear GICv4 could be left in an unknown
state after kexec too.
drivers/irqchip/irq-gic-v3-its.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index d097001c1e3e..0022852ce494 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3172,6 +3172,7 @@ static void its_cpu_init_lpis(void)
val |= GICR_CTLR_ENABLE_LPIS;
writel_relaxed(val, rbase + GICR_CTLR);
+out:
if (gic_rdists->has_vlpis && !gic_rdists->has_rvpeid) {
void __iomem *vlpi_base = gic_data_rdist_vlpi_base();
@@ -3207,7 +3208,6 @@ static void its_cpu_init_lpis(void)
/* Make sure the GIC has seen the above */
dsb(sy);
-out:
gic_data_rdist()->flags |= RD_LOCAL_LPI_ENABLED;
pr_info("GICv3: CPU%d: using %s LPI pending table @%pa\n",
smp_processor_id(),
--
2.44.0.rc0.258.g7320e95886-goog
