[PATCH v2 04/10] irqchip/gic-v5: Serialise ITS invalidation commands

[Sascha Bischoff]

The ITS uses the shared DIDR and EIDR registers to select the DeviceID
and EventID whose translation is to be invalidated. Event
invalidations for different IRQs can overlap, as can an event
invalidation and a device invalidation. The per-IRQ descriptor lock
does not serialise these commands, so writes can interleave and cause
an invalidation to use the DeviceID or EventID of another IRQ being
invalidated concurrently on a different CPU.

Serialise the command register writes and STATUSR.IDLE polls for both
invalidation paths with a per-ITS raw spinlock. The KVM
gicv5_its_set_vcpu_affinity() callback calls the event invalidation
helper via irq_set_vcpu_affinity(), which holds the IRQ descriptor
lock. This path cannot sleep, so use atomic polling.

Fixes: 57d72196dfc8 ("irqchip/gic-v5: Add GICv5 ITS support")
Reported-by: Sashiko AI <sashiko-bot@xxxxxxxxxx>
Link: https://sashiko.dev/#/patchset/20261016155741.979985-1-sascha.bischoff@xxxxxxx?part=11
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sascha Bischoff <sascha.bischoff@xxxxxxx>
---
 drivers/irqchip/irq-gic-v5-its.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v5-its.c b/drivers/irqchip/irq-gic-v5-its.c
index 28e39b065de0e..6d98f3dbe34b6 100644
--- a/drivers/irqchip/irq-gic-v5-its.c
+++ b/drivers/irqchip/irq-gic-v5-its.c
@@ -16,6 +16,7 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/slab.h>
+#include <linux/spinlock.h>
 
 #include <linux/irqchip.h>
 #include <linux/irqchip/arm-gic-v5.h>
@@ -28,6 +29,8 @@
 struct gicv5_its_chip_data {
 	struct	xarray			its_devices;
 	struct	mutex			dev_alloc_lock;
+	/* Event and device invalidation commands share DIDR. */
+	raw_spinlock_t			inv_lock;
 	struct	fwnode_handle		*fwnode;
 	struct gicv5_its_devtab_cfg	devtab_cfgr;
 	void	__iomem			*its_base;
@@ -129,6 +132,8 @@ static int gicv5_its_itt_cache_inv(struct gicv5_its_chip_data *its, u32 device_i
 	eidr = FIELD_PREP(GICV5_ITS_EIDR_EVENTID, event_id);
 	eventr = FIELD_PREP(GICV5_ITS_INV_EVENTR_I, 0x1);
 
+	guard(raw_spinlock_irqsave)(&its->inv_lock);
+
 	its_writeq_relaxed(its, didr, GICV5_ITS_DIDR);
 	its_writel_relaxed(its, eidr, GICV5_ITS_EIDR);
 	its_writel_relaxed(its, eventr, GICV5_ITS_INV_EVENTR);
@@ -371,6 +376,9 @@ static int gicv5_its_device_cache_inv(struct gicv5_its_chip_data *its,
 		  FIELD_PREP(GICV5_ITS_INV_DEVICER_EVENTID_BITS,
 			     its_dev->itt_cfg.event_id_bits)	|
 		  FIELD_PREP(GICV5_ITS_INV_DEVICER_L1, 0x0);
+
+	guard(raw_spinlock_irqsave)(&its->inv_lock);
+
 	its_writeq_relaxed(its, didr, GICV5_ITS_DIDR);
 	its_writel_relaxed(its, devicer, GICV5_ITS_INV_DEVICER);
 
@@ -1112,6 +1120,7 @@ static int __init gicv5_its_init_bases(void __iomem *its_base, struct fwnode_han
 		return -ENOMEM;
 
 	mutex_init(&its_node->dev_alloc_lock);
+	raw_spin_lock_init(&its_node->inv_lock);
 	xa_init(&its_node->its_devices);
 	its_node->fwnode = handle;
 	its_node->its_base = its_base;

-- 
2.34.1