[PATCH 6.1 107/195] irqchip/gic-v3-its: Do not assume vPE tables are preallocated

Greg Kroah-Hartman
2024-02-27T14:18:34Z

From: Oliver Upton <oliver.upton@linux.dev>

commit ec4308ecfc887128a468f03fb66b767559c57c23 upstream.

The GIC/ITS code is designed to ensure to 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 it is expected to
allocate a new vPE table at boot.

This works as intended when initializing an ITS, however when setting up a
redistributor in cpu_init_lpis() the early return for preallocated RD
tables skips straight past the 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.

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.

Fixes: 6479450f72c1 ("irqchip/gic-v4: Fix occasional VLPI drop")
Reported-by: George Cherian <gcherian@marvell.com>
Co-developed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240219185809.286724-2-oliver.upton@linux.dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/irqchip/irq-gic-v3-its.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3161,6 +3161,7 @@ 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();

@@ -3196,7 +3197,6 @@ 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(),