[PATCH v2 3/3] irqchip/gic-v3: Relax polling of GIC{R,D}_CTLR.RWP

Marc Zyngier
2022-04-06T02:07:55Z

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@kernel.org>
---
drivers/irqchip/irq-gic-v3.c | 38 +++++++++++++++++-------------------
1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 4d8517232f1e..93cfd2b1efdd 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)
@@ -420,7 +419,11 @@ static int gic_irq_set_irqchip_state(struct irq_data *d,
break;

case IRQCHIP_STATE_MASKED:
- reg = val ? GICD_ICENABLER : GICD_ISENABLER;
+ if (val) {
+ gic_mask_irq(d);
+ return 0;
+ }
+ reg = GICD_ISENABLER;
break;

default:
@@ -574,7 +577,6 @@ 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 +592,14 @@ 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);
@@ -807,8 +806,8 @@ static void __init gic_dist_init(void)
for (i = 0; i < GIC_ESPI_NR; i += 4)
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);
+ /* Now do the common stuff */
+ 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) {
@@ -816,8 +815,9 @@ static void __init gic_dist_init(void)
val |= GICD_CTLR_nASSGIreq;
}

- /* Enable distributor with ARE, Group1 */
+ /* Enable distributor with ARE, Group1, and wait for it to drain */
writel_relaxed(val, base + GICD_CTLR);
+ gic_dist_wait_for_rwp();

/*
* Set all global interrupts to the boot CPU only. ARE must be
@@ -1298,8 +1298,6 @@ 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