linux-kernel - [PATCH 3/3] irqchip/gic-v3: Relax polling of GIC{R,D}

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Message-Id: <20220315165034.794482-4-maz@kernel.org>
Date:   Tue, 15 Mar 2022 16:50:34 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andre Przywara <andre.przywara@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Auger <eric.auger@...hat.com>
Subject: [PATCH 3/3] irqchip/gic-v3: Relax polling of GIC{R,D}_CTLR.RWP

Recent work on the KVM GIC emulation has revealed that the GICv3
driver is a bit RWP-happy, as it polls this bit for each and
every write MMIO access involving a single interrupt.

As it turns out, polling RWP is only required when:
- Disabling an SGI, PPI or SPI
- Disabling LPIs at the redistributor level
- Disabling groups
- Enabling ARE
- Dealing with DPG*

Simplify the driver by removing all the other instances of RWP
polling, and add the one that was missing when enabling the distributor
(as that's where we set ARE).

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 drivers/irqchip/irq-gic-v3.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 363bfe172033..05ff7fef64cb 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -352,28 +352,27 @@ static int gic_peek_irq(struct irq_data *d, u32 offset)
 
 static void gic_poke_irq(struct irq_data *d, u32 offset)
 {
-	void (*rwp_wait)(void);
 	void __iomem *base;
 	u32 index, mask;
 
 	offset = convert_offset_index(d, offset, &index);
 	mask = 1 << (index % 32);
 
-	if (gic_irq_in_rdist(d)) {
+	if (gic_irq_in_rdist(d))
 		base = gic_data_rdist_sgi_base();
-		rwp_wait = gic_redist_wait_for_rwp;
-	} else {
+	else
 		base = gic_data.dist_base;
-		rwp_wait = gic_dist_wait_for_rwp;
-	}
 
 	writel_relaxed(mask, base + offset + (index / 32) * 4);
-	rwp_wait();
 }
 
 static void gic_mask_irq(struct irq_data *d)
 {
 	gic_poke_irq(d, GICD_ICENABLER);
+	if (gic_irq_in_rdist(d))
+		gic_redist_wait_for_rwp();
+	else
+		gic_dist_wait_for_rwp();
 }
 
 static void gic_eoimode1_mask_irq(struct irq_data *d)
@@ -574,7 +573,6 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 {
 	enum gic_intid_range range;
 	unsigned int irq = gic_irq(d);
-	void (*rwp_wait)(void);
 	void __iomem *base;
 	u32 offset, index;
 	int ret;
@@ -590,17 +588,14 @@ static int gic_set_type(struct irq_data *d, unsigned int type)
 	    type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
 		return -EINVAL;
 
-	if (gic_irq_in_rdist(d)) {
+	if (gic_irq_in_rdist(d))
 		base = gic_data_rdist_sgi_base();
-		rwp_wait = gic_redist_wait_for_rwp;
-	} else {
+	else
 		base = gic_data.dist_base;
-		rwp_wait = gic_dist_wait_for_rwp;
-	}
 
 	offset = convert_offset_index(d, GICD_ICFGR, &index);
 
-	ret = gic_configure_irq(index, type, base + offset, rwp_wait);
+	ret = gic_configure_irq(index, type, base + offset, NULL);
 	if (ret && (range == PPI_RANGE || range == EPPI_RANGE)) {
 		/* Misconfigured PPIs are usually not fatal */
 		pr_warn("GIC: PPI INTID%d is secure or misconfigured\n", irq);
@@ -808,7 +803,7 @@ static void __init gic_dist_init(void)
 		writel_relaxed(GICD_INT_DEF_PRI_X4, base + GICD_IPRIORITYRnE + i);
 
 	/* Now do the common stuff, and wait for the distributor to drain */
-	gic_dist_config(base, GIC_LINE_NR, gic_dist_wait_for_rwp);
+	gic_dist_config(base, GIC_LINE_NR, NULL);
 
 	val = GICD_CTLR_ARE_NS | GICD_CTLR_ENABLE_G1A | GICD_CTLR_ENABLE_G1;
 	if (gic_data.rdists.gicd_typer2 & GICD_TYPER2_nASSGIcap) {
@@ -818,6 +813,7 @@ static void __init gic_dist_init(void)
 
 	/* Enable distributor with ARE, Group1 */
 	writel_relaxed(val, base + GICD_CTLR);
+	gic_dist_wait_for_rwp();
 
 	/*
 	 * Set all global interrupts to the boot CPU only. ARE must be
@@ -1293,8 +1289,6 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 	 */
 	if (enabled)
 		gic_unmask_irq(d);
-	else
-		gic_dist_wait_for_rwp();
 
 	irq_data_update_effective_affinity(d, cpumask_of(cpu));
 
-- 
2.34.1