linux-kernel - [tip: irq/urgent] irqchip/gic-v3-its: Fix VSYNC referencing an unmapped VPE on GIC v4.1

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Message-ID: <171265419457.10875.5533397957548411107.tip-bot2@tip-bot2>
Date: Tue, 09 Apr 2024 09:16:34 -0000
From: "tip-bot2 for Nianyao Tang" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Nianyao Tang <tangnianyao@...wei.com>,
 Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <maz@...nel.org>,
 Zenghui Yu <yuzenghui@...wei.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: irq/urgent] irqchip/gic-v3-its: Fix VSYNC referencing an
 unmapped VPE on GIC v4.1

The following commit has been merged into the irq/urgent branch of tip:

Commit-ID:     80e9963fb3b5509dfcabe9652d56bf4b35542055
Gitweb:        https://git.kernel.org/tip/80e9963fb3b5509dfcabe9652d56bf4b35542055
Author:        Nianyao Tang <tangnianyao@...wei.com>
AuthorDate:    Sat, 06 Apr 2024 02:27:37 
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 09 Apr 2024 11:11:18 +02:00

irqchip/gic-v3-its: Fix VSYNC referencing an unmapped VPE on GIC v4.1

As per the GICv4.1 spec (Arm IHI 0069H, 5.3.19):

 "A VMAPP with {V, Alloc}=={0, x} is self-synchronizing, This means the ITS
  command queue does not show the command as consumed until all of its
  effects are completed."

Furthermore, VSYNC is allowed to deliver an SError when referencing a
non existent VPE.

By these definitions, a VMAPP followed by a VSYNC is a bug, as the
later references a VPE that has been unmapped by the former.

Fix it by eliding the VSYNC in this scenario.

Fixes: 64edfaa9a234 ("irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP")
Signed-off-by: Nianyao Tang <tangnianyao@...wei.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Marc Zyngier <maz@...nel.org>
Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>
Link: https://lore.kernel.org/r/20240406022737.3898763-1-tangnianyao@huawei.com
---
 drivers/irqchip/irq-gic-v3-its.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index fca888b..2a537cb 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -786,6 +786,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 					   struct its_cmd_block *cmd,
 					   struct its_cmd_desc *desc)
 {
+	struct its_vpe *vpe = valid_vpe(its, desc->its_vmapp_cmd.vpe);
 	unsigned long vpt_addr, vconf_addr;
 	u64 target;
 	bool alloc;
@@ -798,6 +799,11 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 		if (is_v4_1(its)) {
 			alloc = !atomic_dec_return(&desc->its_vmapp_cmd.vpe->vmapp_count);
 			its_encode_alloc(cmd, alloc);
+			/*
+			 * Unmapping a VPE is self-synchronizing on GICv4.1,
+			 * no need to issue a VSYNC.
+			 */
+			vpe = NULL;
 		}
 
 		goto out;
@@ -832,7 +838,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 out:
 	its_fixup_cmd(cmd);
 
-	return valid_vpe(its, desc->its_vmapp_cmd.vpe);
+	return vpe;
 }
 
 static struct its_vpe *its_build_vmapti_cmd(struct its_node *its,