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@vger.kernel.org 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 ---
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(),
The following commit has been merged into the irq/urgent branch of tip:
Commit-ID: ec4308ecfc887128a468f03fb66b767559c57c23 Gitweb: https://git.kernel.org/tip/ec4308ecfc887128a468f03fb66b767559c57c23 Author: Oliver Upton oliver.upton@linux.dev AuthorDate: Mon, 19 Feb 2024 18:58:06 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Wed, 21 Feb 2024 21:11:20 +01:00
irqchip/gic-v3-its: Do not assume vPE tables are preallocated
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 --- 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 53abd47..b822752 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -3181,6 +3181,7 @@ 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();
@@ -3216,7 +3217,6 @@ 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(),
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