FAILED: patch "[PATCH] irqchip/gic-v3-its: Do not assume vPE tables are preallocated" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x ec4308ecfc887128a468f03fb66b767559c57c23
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024022650-washroom-undusted-2aff@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

ec4308ecfc88 ("irqchip/gic-v3-its: Do not assume vPE tables are preallocated")
c0cdc89072a3 ("irqchip/gic-v3-its: Give the percpu rdist struct its own flags field")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ec4308ecfc887128a468f03fb66b767559c57c23 Mon Sep 17 00:00:00 2001
From: Oliver Upton <oliver.upton@linux.dev>
Date: Mon, 19 Feb 2024 18:58:06 +0000
Subject: [PATCH] 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

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 53abd4779914..b822752c4261 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(),