linux-kernel - [PATCH] irqchip/gic-v3-its: Don't need VSYNC if VMAPP with {V, Alloc}=={0, x}

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Message-ID: <20240402114147.3788881-1-tangnianyao@huawei.com>
Date: Tue, 2 Apr 2024 11:41:47 +0000
From: t00849498 <tangnianyao@...wei.com>
To: <maz@...nel.org>, <tglx@...utronix.de>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC: <guoyang2@...wei.com>, <wangwudi@...ilicon.com>, <tangnianyao@...wei.com>
Subject: [PATCH] irqchip/gic-v3-its: Don't need VSYNC if VMAPP with {V, Alloc}=={0, x}

>From GIC spec, 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. A VSYNC with unmapped
vpeid is not needed.

Signed-off-by: t00849498 <tangnianyao@...wei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index fca888b36680..a0ca5dcbb245 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -789,6 +789,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 	unsigned long vpt_addr, vconf_addr;
 	u64 target;
 	bool alloc;
+	bool unmap_v4_1 = !desc->its_vmapp_cmd.valid && is_v4_1(its);
 
 	its_encode_cmd(cmd, GITS_CMD_VMAPP);
 	its_encode_vpeid(cmd, desc->its_vmapp_cmd.vpe->vpe_id);
@@ -832,6 +833,9 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 out:
 	its_fixup_cmd(cmd);
 
+	if (unmap_v4_1)
+		return NULL;
+
 	return valid_vpe(its, desc->its_vmapp_cmd.vpe);
 }
 
-- 
2.30.0