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Subject[tip: irq/core] irqchip/gic-v4.1: Plumb get/set_irqchip_state SGI callbacks
The following commit has been merged into the irq/core branch of tip:

Commit-ID: 7017ff0ee1de9d45fafee88a4e7890cce92f482e
Gitweb: https://git.kernel.org/tip/7017ff0ee1de9d45fafee88a4e7890cce92f482e
Author: Marc Zyngier <maz@kernel.org>
AuthorDate: Wed, 04 Mar 2020 20:33:18
Committer: Marc Zyngier <maz@kernel.org>
CommitterDate: Tue, 24 Mar 2020 12:05:09

irqchip/gic-v4.1: Plumb get/set_irqchip_state SGI callbacks

To implement the get/set_irqchip_state callbacks (limited to the
PENDING state), we have to use a particular set of hacks:

- Reading the pending state is done by using a pair of new redistributor
registers (GICR_VSGIR, GICR_VSGIPENDR), which allow the 16 interrupts
state to be retrieved.
- Setting the pending state is done by generating it as we'd otherwise do
for a guest (writing to GITS_SGIR).
- Clearing the pending state is done by emitting a VSGI command with the
"clear" bit set.

This requires some interesting locking though:
- When talking to the redistributor, we must make sure that the VPE
affinity doesn't change, hence taking the VPE lock.
- At the same time, we must ensure that nobody accesses the same
redistributor's GICR_VSGIR registers for a different VPE, which
would corrupt the reading of the pending bits. We thus take the
per-RD spinlock. Much fun.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20200304203330.4967-12-maz@kernel.org
---
drivers/irqchip/irq-gic-v3-its.c | 77 +++++++++++++++++++++++++++++-
include/linux/irqchip/arm-gic-v3.h | 14 +++++-
2 files changed, 91 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index bc6666a..c614f0c 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3972,11 +3972,88 @@ static int its_sgi_set_affinity(struct irq_data *d,
return IRQ_SET_MASK_OK;
}

+static int its_sgi_set_irqchip_state(struct irq_data *d,
+ enum irqchip_irq_state which,
+ bool state)
+{
+ if (which != IRQCHIP_STATE_PENDING)
+ return -EINVAL;
+
+ if (state) {
+ struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
+ struct its_node *its = find_4_1_its();
+ u64 val;
+
+ val = FIELD_PREP(GITS_SGIR_VPEID, vpe->vpe_id);
+ val |= FIELD_PREP(GITS_SGIR_VINTID, d->hwirq);
+ writeq_relaxed(val, its->sgir_base + GITS_SGIR - SZ_128K);
+ } else {
+ its_configure_sgi(d, true);
+ }
+
+ return 0;
+}
+
+static int its_sgi_get_irqchip_state(struct irq_data *d,
+ enum irqchip_irq_state which, bool *val)
+{
+ struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
+ void __iomem *base;
+ unsigned long flags;
+ u32 count = 1000000; /* 1s! */
+ u32 status;
+ int cpu;
+
+ if (which != IRQCHIP_STATE_PENDING)
+ return -EINVAL;
+
+ /*
+ * Locking galore! We can race against two different events:
+ *
+ * - Concurent vPE affinity change: we must make sure it cannot
+ * happen, or we'll talk to the wrong redistributor. This is
+ * identical to what happens with vLPIs.
+ *
+ * - Concurrent VSGIPENDR access: As it involves accessing two
+ * MMIO registers, this must be made atomic one way or another.
+ */
+ cpu = vpe_to_cpuid_lock(vpe, &flags);
+ raw_spin_lock(&gic_data_rdist_cpu(cpu)->rd_lock);
+ base = gic_data_rdist_cpu(cpu)->rd_base + SZ_128K;
+ writel_relaxed(vpe->vpe_id, base + GICR_VSGIR);
+ do {
+ status = readl_relaxed(base + GICR_VSGIPENDR);
+ if (!(status & GICR_VSGIPENDR_BUSY))
+ goto out;
+
+ count--;
+ if (!count) {
+ pr_err_ratelimited("Unable to get SGI status\n");
+ goto out;
+ }
+ cpu_relax();
+ udelay(1);
+ } while (count);
+
+out:
+ raw_spin_unlock(&gic_data_rdist_cpu(cpu)->rd_lock);
+ vpe_to_cpuid_unlock(vpe, flags);
+
+ if (!count)
+ return -ENXIO;
+
+ *val = !!(status & (1 << d->hwirq));
+
+ return 0;
+}
+
static struct irq_chip its_sgi_irq_chip = {
.name = "GICv4.1-sgi",
.irq_mask = its_sgi_mask_irq,
.irq_unmask = its_sgi_unmask_irq,
.irq_set_affinity = its_sgi_set_affinity,
+ .irq_set_irqchip_state = its_sgi_set_irqchip_state,
+ .irq_get_irqchip_state = its_sgi_get_irqchip_state,
};

static int its_sgi_irq_domain_alloc(struct irq_domain *domain,
diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
index fd3be49..590cdbe 100644
--- a/include/linux/irqchip/arm-gic-v3.h
+++ b/include/linux/irqchip/arm-gic-v3.h
@@ -345,6 +345,15 @@
#define GICR_VPENDBASER_4_1_VGRP1EN (1ULL << 58)
#define GICR_VPENDBASER_4_1_VPEID GENMASK_ULL(15, 0)

+#define GICR_VSGIR 0x0080
+
+#define GICR_VSGIR_VPEID GENMASK(15, 0)
+
+#define GICR_VSGIPENDR 0x0088
+
+#define GICR_VSGIPENDR_BUSY (1U << 31)
+#define GICR_VSGIPENDR_PENDING GENMASK(15, 0)
+
/*
* ITS registers, offsets from ITS_base
*/
@@ -368,6 +377,11 @@

#define GITS_TRANSLATER 0x10040

+#define GITS_SGIR 0x20020
+
+#define GITS_SGIR_VPEID GENMASK_ULL(47, 32)
+#define GITS_SGIR_VINTID GENMASK_ULL(3, 0)
+
#define GITS_CTLR_ENABLE (1U << 0)
#define GITS_CTLR_ImDe (1U << 1)
#define GITS_CTLR_ITS_NUMBER_SHIFT 4
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