Message-Id: <20251112-implement-msi-domain-v1-2-103dd123de14@linux.ibm.com>
Date: Wed, 12 Nov 2025 16:40:45 +0100
From: Tobias Schumacher <ts@...ux.ibm.com>
To: Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Gerd Bayer <gbayer@...ux.ibm.com>, Halil Pasic <pasic@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Tobias Schumacher <ts@...ux.ibm.com>
Subject: [PATCH 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

s390 is one of the last architectures using the legacy API for setup and
teardown of PCI MSI IRQs. Migrate the s390 IRQ allocation and teardown
to the MSI parent domain API. For details, see:

https://lore.kernel.org/lkml/20221111120501.026511281@linutronix.de

In detail, create an MSI parent domain for zpci which is used by
all PCI devices. When a PCI device sets up MSI or MSI-X IRQs, the
library creates a per-device IRQ domain for this device, which is
be used by the device for allocating and freeing IRQs.

The per-device domain delegates this allocation and freeing to the
parent-domain. In the end, the corresponding callbacks of the parent
domain are responsible for allocating and freeing the IRQs.

The allocation is split into two parts:
- zpci_msi_prepare() is called once for each device and allocates the
  required resources. On s390, each PCI function has its own airq
  vector and a summary bit, which must be configured once per function.
  This is done in prepare().
- zpci_msi_alloc() can be called multiple times for allocating one or
  more MSI/MSI-X IRQs. This creates a mapping between the virtual IRQ
  number in the kernel and the hardware IRQ number.

Freeing is split into two counterparts:
- zpci_msi_free() reverts the effects of zpci_msi_alloc() and
- zpci_msi_teardown() reverts the effects of zpci_msi_prepare(). This is
  callend once when all IRQs are freed before a device is removed.

Since the parent domain in the end allocates the IRQs, the hwirq
encoding must be unambiguous for all IRQs of all devices. This is
achieved by encoding the hwirq using the PCI function id and the MSI
index.

Signed-off-by: Tobias Schumacher <ts@...ux.ibm.com>
---
 arch/s390/Kconfig           |   1 +
 arch/s390/include/asm/pci.h |   1 +
 arch/s390/pci/pci_bus.c     |   1 +
 arch/s390/pci/pci_irq.c     | 323 +++++++++++++++++++++++++++-----------------
 4 files changed, 203 insertions(+), 123 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index df22b10d91415e1ed183cc8add9ad0ac4293c50e..739a9a9a86a277be1ba750cb2e98af0547df89fd 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -251,6 +251,7 @@ config S390
 	select HOTPLUG_SMT
 	select IOMMU_HELPER		if PCI
 	select IOMMU_SUPPORT		if PCI
+  select IRQ_MSI_LIB if PCI
 	select KASAN_VMALLOC if KASAN
 	select LOCK_MM_AND_FIND_VMA
 	select MMU_GATHER_MERGE_VMAS
diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index a32f465ecf73a5cc3408a312d94ec888d62848cc..462e87bdb7acdfa4e7df0f9ca8e82c269e1f98aa 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -310,6 +310,7 @@ int zpci_dma_exit_device(struct zpci_dev *zdev);
 /* IRQ */
 int __init zpci_irq_init(void);
 void __init zpci_irq_exit(void);
+void zpci_set_msi_parent_domain(struct zpci_bus *zbus);
 
 /* FMB */
 int zpci_fmb_enable_device(struct zpci_dev *);
diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
index be8c697fea0cc755cfdb4fb0a9e3b95183bec0dc..2be33cfb8970409db4fcb75ea73543f49b583a5c 100644
--- a/arch/s390/pci/pci_bus.c
+++ b/arch/s390/pci/pci_bus.c
@@ -210,6 +210,7 @@ static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *fr, s
 	}
 
 	zbus->bus = bus;
+	zpci_set_msi_parent_domain(zbus);
 
 	return 0;
 }
diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
index e73be96ce5fe6473fc193d65b8f0ff635d6a98ba..7412906b5fec695aa62155a8ecc34fb1f93e0f4b 100644
--- a/arch/s390/pci/pci_irq.c
+++ b/arch/s390/pci/pci_irq.c
@@ -7,6 +7,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/pci.h>
 #include <linux/msi.h>
+#include <linux/irqchip/irq-msi-lib.h>
 #include <linux/smp.h>
 
 #include <asm/isc.h>
@@ -29,6 +30,8 @@ static struct airq_iv *zpci_sbv;
  */
 static struct airq_iv **zpci_ibv;
 
+static struct irq_domain *zpci_msi_parent_domain;
+
 /* Modify PCI: Register floating adapter interruptions */
 static int zpci_set_airq(struct zpci_dev *zdev)
 {
@@ -110,19 +113,6 @@ static int zpci_set_irq(struct zpci_dev *zdev)
 	return rc;
 }
 
-/* Clear adapter interruptions */
-static int zpci_clear_irq(struct zpci_dev *zdev)
-{
-	int rc;
-
-	if (irq_delivery == DIRECTED)
-		rc = zpci_clear_directed_irq(zdev);
-	else
-		rc = zpci_clear_airq(zdev);
-
-	return rc;
-}
-
 static int zpci_set_irq_affinity(struct irq_data *data, const struct cpumask *dest,
 				 bool force)
 {
@@ -137,16 +127,40 @@ static int zpci_set_irq_affinity(struct irq_data *data, const struct cpumask *de
 	return IRQ_SET_MASK_OK;
 }
 
+static void zpci_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct zpci_dev *zdev = to_zpci_dev(desc->dev);
+
+	if (irq_delivery == DIRECTED) {
+		int cpu = 0;
+
+		if (desc->affinity)
+			cpu = cpumask_first(&desc->affinity->mask);
+		else
+			cpu = 0;
+		msg->address_lo = zdev->msi_addr & 0xff0000ff;
+		msg->address_lo |= (smp_cpu_get_cpu_address(cpu) << 8);
+	} else {
+		msg->address_lo = zdev->msi_addr & 0xffffffff;
+	}
+	msg->address_hi = zdev->msi_addr >> 32;
+	msg->data = data->hwirq - zdev->msi_first_bit;
+}
+
 static struct irq_chip zpci_irq_chip = {
 	.name = "PCI-MSI",
+	.irq_set_affinity = irq_chip_set_affinity_parent,
 	.irq_unmask = pci_msi_unmask_irq,
 	.irq_mask = pci_msi_mask_irq,
+	.irq_compose_msi_msg = zpci_compose_msi_msg
 };
 
 static void zpci_handle_cpu_local_irq(bool rescan)
 {
 	struct airq_iv *dibv = zpci_ibv[smp_processor_id()];
 	union zpci_sic_iib iib = {{0}};
+	irq_hw_number_t hwirq;
 	unsigned long bit;
 	int irqs_on = 0;
 
@@ -164,7 +178,8 @@ static void zpci_handle_cpu_local_irq(bool rescan)
 			continue;
 		}
 		inc_irq_stat(IRQIO_MSI);
-		generic_handle_irq(airq_iv_get_data(dibv, bit));
+		hwirq = airq_iv_get_ptr(dibv, bit);
+		generic_handle_domain_irq(zpci_msi_parent_domain, hwirq);
 	}
 }
 
@@ -229,6 +244,7 @@ static void zpci_floating_irq_handler(struct airq_struct *airq,
 				      struct tpi_info *tpi_info)
 {
 	union zpci_sic_iib iib = {{0}};
+	irq_hw_number_t hwirq;
 	unsigned long si, ai;
 	struct airq_iv *aibv;
 	int irqs_on = 0;
@@ -256,7 +272,9 @@ static void zpci_floating_irq_handler(struct airq_struct *airq,
 				break;
 			inc_irq_stat(IRQIO_MSI);
 			airq_iv_lock(aibv, ai);
-			generic_handle_irq(airq_iv_get_data(aibv, ai));
+
+			hwirq = airq_iv_get_ptr(aibv, ai);
+			generic_handle_domain_irq(zpci_msi_parent_domain, hwirq);
 			airq_iv_unlock(aibv, ai);
 		}
 	}
@@ -278,7 +296,7 @@ static int __alloc_airq(struct zpci_dev *zdev, int msi_vecs,
 		zdev->aisb = *bit;
 
 		/* Create adapter interrupt vector */
-		zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA | AIRQ_IV_BITLOCK, NULL);
+		zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_PTR | AIRQ_IV_BITLOCK, NULL);
 		if (!zdev->aibv)
 			return -ENOMEM;
 
@@ -290,146 +308,197 @@ static int __alloc_airq(struct zpci_dev *zdev, int msi_vecs,
 	return 0;
 }
 
-int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
+static struct airq_struct zpci_airq = {
+	.handler = zpci_floating_irq_handler,
+	.isc = PCI_ISC,
+};
+
+/*
+ * Encode the hwirq number for the parent domain. The encoding must be unique
+ * for each IRQ of each device in the parent domain, so it uses the fid to
+ * identify the device and the msi_index to identify the IRQ within that device.
+ */
+static inline irq_hw_number_t zpci_encode_hwirq(u32 fid, u16 msi_index)
 {
-	unsigned int hwirq, msi_vecs, irqs_per_msi, i, cpu;
-	struct zpci_dev *zdev = to_zpci(pdev);
-	struct msi_desc *msi;
-	struct msi_msg msg;
-	unsigned long bit;
-	int cpu_addr;
-	int rc, irq;
+	return ((irq_hw_number_t)fid << 32) | msi_index;
+}
 
-	zdev->aisb = -1UL;
-	zdev->msi_first_bit = -1U;
+static inline u16 zpci_decode_hwirq_msi_index(irq_hw_number_t irq)
+{
+	return irq & 0xFFFF;
+}
+
+static int zpci_msi_prepare(struct irq_domain *domain,
+			    struct device *dev, int nvec,
+			    msi_alloc_info_t *info)
+{
+	struct zpci_dev *zdev = to_zpci_dev(dev);
+	struct pci_dev *pdev = to_pci_dev(dev);
+	unsigned long bit;
+	int msi_vecs, rc;
 
 	msi_vecs = min_t(unsigned int, nvec, zdev->max_msi);
-	if (msi_vecs < nvec) {
+	if (msi_vecs < nvec)
 		pr_info("%s requested %d irqs, allocate system limit of %d",
 			pci_name(pdev), nvec, zdev->max_msi);
-	}
 
 	rc = __alloc_airq(zdev, msi_vecs, &bit);
-	if (rc < 0)
+	if (rc) {
+		pr_err("Allocating AIRQ for %s failed\n", pci_name(pdev));
 		return rc;
+	}
 
-	/*
-	 * Request MSI interrupts:
-	 * When using MSI, nvec_used interrupt sources and their irq
-	 * descriptors are controlled through one msi descriptor.
-	 * Thus the outer loop over msi descriptors shall run only once,
-	 * while two inner loops iterate over the interrupt vectors.
-	 * When using MSI-X, each interrupt vector/irq descriptor
-	 * is bound to exactly one msi descriptor (nvec_used is one).
-	 * So the inner loops are executed once, while the outer iterates
-	 * over the MSI-X descriptors.
-	 */
-	hwirq = bit;
-	msi_for_each_desc(msi, &pdev->dev, MSI_DESC_NOTASSOCIATED) {
-		if (hwirq - bit >= msi_vecs)
-			break;
-		irqs_per_msi = min_t(unsigned int, msi_vecs, msi->nvec_used);
-		irq = __irq_alloc_descs(-1, 0, irqs_per_msi, 0, THIS_MODULE,
-					(irq_delivery == DIRECTED) ?
-					msi->affinity : NULL);
-		if (irq < 0)
-			return -ENOMEM;
-
-		for (i = 0; i < irqs_per_msi; i++) {
-			rc = irq_set_msi_desc_off(irq, i, msi);
-			if (rc)
-				return rc;
-			irq_set_chip_and_handler(irq + i, &zpci_irq_chip,
-						 handle_percpu_irq);
-		}
-
-		msg.data = hwirq - bit;
+	zdev->msi_first_bit = bit;
+	rc = zpci_set_irq(zdev);
+	if (rc) {
+		pr_err("Registering floating adapter interruptions for %s failed\n",
+		       pci_name(pdev));
 		if (irq_delivery == DIRECTED) {
-			if (msi->affinity)
-				cpu = cpumask_first(&msi->affinity->mask);
-			else
-				cpu = 0;
-			cpu_addr = smp_cpu_get_cpu_address(cpu);
-
-			msg.address_lo = zdev->msi_addr & 0xff0000ff;
-			msg.address_lo |= (cpu_addr << 8);
-
-			for_each_possible_cpu(cpu) {
-				for (i = 0; i < irqs_per_msi; i++)
-					airq_iv_set_data(zpci_ibv[cpu],
-							 hwirq + i, irq + i);
-			}
+			airq_iv_free(zpci_ibv[0], zdev->msi_first_bit, msi_vecs);
 		} else {
-			msg.address_lo = zdev->msi_addr & 0xffffffff;
-			for (i = 0; i < irqs_per_msi; i++)
-				airq_iv_set_data(zdev->aibv, hwirq + i, irq + i);
+			zpci_clear_airq(zdev);
+			airq_iv_release(zdev->aibv);
+			zdev->aibv = NULL;
+			airq_iv_free_bit(zpci_sbv, zdev->aisb);
+			zdev->aisb = -1UL;
 		}
-		msg.address_hi = zdev->msi_addr >> 32;
-		pci_write_msi_msg(irq, &msg);
-		hwirq += irqs_per_msi;
+		zdev->msi_first_bit = -1U;
+		return rc;
 	}
 
-	zdev->msi_first_bit = bit;
-	zdev->msi_nr_irqs = hwirq - bit;
+	zdev->msi_nr_irqs = msi_vecs;
 
-	rc = zpci_set_irq(zdev);
-	if (rc)
-		return rc;
+	return 0;
+}
 
-	return (zdev->msi_nr_irqs == nvec) ? 0 : zdev->msi_nr_irqs;
+static void zpci_msi_teardown_directed(struct zpci_dev *zdev)
+{
+	zpci_clear_directed_irq(zdev);
+	airq_iv_free(zpci_ibv[0], zdev->msi_first_bit, zdev->max_msi);
+	zdev->msi_first_bit = -1U;
 }
 
-void arch_teardown_msi_irqs(struct pci_dev *pdev)
+static void zpci_msi_teardown_floating(struct zpci_dev *zdev)
 {
-	struct zpci_dev *zdev = to_zpci(pdev);
-	struct msi_desc *msi;
-	unsigned int i;
-	int rc;
+	zpci_clear_airq(zdev);
+	airq_iv_release(zdev->aibv);
+	zdev->aibv = NULL;
+	airq_iv_free_bit(zpci_sbv, zdev->aisb);
+	zdev->aisb = -1UL;
+	zdev->msi_first_bit = -1U;
+}
 
-	/* Disable interrupts */
-	rc = zpci_clear_irq(zdev);
-	if (rc)
-		return;
+static void zpci_msi_teardown(struct irq_domain *domain, msi_alloc_info_t *arg)
+{
+	struct zpci_dev *zdev = to_zpci_dev(domain->dev);
+
+	if (irq_delivery == DIRECTED)
+		zpci_msi_teardown_directed(zdev);
+	else
+		zpci_msi_teardown_floating(zdev);
+}
+
+static int zpci_msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
+				 unsigned int nr_irqs, void *args)
+{
+	struct msi_desc *desc = ((msi_alloc_info_t *)args)->desc;
+	struct zpci_dev *zdev = to_zpci_dev(desc->dev);
+	irq_hw_number_t hwirq;
+	unsigned long bit;
+	int i;
+
+	bit = zdev->msi_first_bit + desc->msi_index;
+	hwirq = zpci_encode_hwirq(zdev->fid, desc->msi_index);
+
+	if (desc->msi_index + nr_irqs > zdev->max_msi)
+		return -EINVAL;
+
+	for (i = 0; i < nr_irqs; i++) {
+		irq_domain_set_info(domain, virq + i, hwirq + i,
+				    &zpci_irq_chip, zdev,
+				    handle_percpu_irq, NULL, NULL);
 
-	/* Release MSI interrupts */
-	msi_for_each_desc(msi, &pdev->dev, MSI_DESC_ASSOCIATED) {
-		for (i = 0; i < msi->nvec_used; i++) {
-			irq_set_msi_desc(msi->irq + i, NULL);
-			irq_free_desc(msi->irq + i);
+		if (irq_delivery == DIRECTED) {
+			airq_iv_set_ptr(zpci_ibv[smp_processor_id()],
+					bit + i, hwirq + i);
+		} else {
+			airq_iv_set_ptr(zdev->aibv, bit + i, hwirq + i);
 		}
-		msi->msg.address_lo = 0;
-		msi->msg.address_hi = 0;
-		msi->msg.data = 0;
-		msi->irq = 0;
 	}
 
-	if (zdev->aisb != -1UL) {
-		zpci_ibv[zdev->aisb] = NULL;
-		airq_iv_free_bit(zpci_sbv, zdev->aisb);
-		zdev->aisb = -1UL;
-	}
-	if (zdev->aibv) {
-		airq_iv_release(zdev->aibv);
-		zdev->aibv = NULL;
-	}
+	return 0;
+}
 
-	if ((irq_delivery == DIRECTED) && zdev->msi_first_bit != -1U)
-		airq_iv_free(zpci_ibv[0], zdev->msi_first_bit, zdev->msi_nr_irqs);
+static void zpci_msi_domain_free(struct irq_domain *domain, unsigned int virq,
+				 unsigned int nr_irqs)
+{
+	irq_hw_number_t hwirq;
+	struct irq_data *d;
+	u16 msi_index;
+	int i;
+
+	for (i = 0; i < nr_irqs; i++) {
+		d = irq_domain_get_irq_data(domain, virq + i);
+		hwirq = d->hwirq;
+		msi_index = zpci_decode_hwirq_msi_index(hwirq);
+		irq_domain_reset_irq_data(d);
+	}
 }
 
-bool arch_restore_msi_irqs(struct pci_dev *pdev)
+static const struct irq_domain_ops zpci_msi_domain_ops = {
+	.alloc = zpci_msi_domain_alloc,
+	.free  = zpci_msi_domain_free
+};
+
+static bool zpci_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
+				   struct irq_domain *real_parent,
+				   struct msi_domain_info *info)
 {
-	struct zpci_dev *zdev = to_zpci(pdev);
+	if (!msi_lib_init_dev_msi_info(dev, domain, real_parent, info))
+		return false;
+
+	info->ops->msi_prepare = zpci_msi_prepare;
+	info->ops->msi_teardown = zpci_msi_teardown;
 
-	zpci_set_irq(zdev);
 	return true;
 }
 
-static struct airq_struct zpci_airq = {
-	.handler = zpci_floating_irq_handler,
-	.isc = PCI_ISC,
+static const struct msi_parent_ops zpci_msi_parent_ops = {
+	.supported_flags   = MSI_GENERIC_FLAGS_MASK	|
+			     MSI_FLAG_PCI_MSIX		|
+			     MSI_FLAG_MULTI_PCI_MSI,
+	.required_flags	   = MSI_FLAG_USE_DEF_DOM_OPS  |
+			     MSI_FLAG_USE_DEF_CHIP_OPS |
+			     MSI_FLAG_PCI_MSI_MASK_PARENT,
+	.init_dev_msi_info = zpci_init_dev_msi_info
 };
 
+static int __init zpci_create_parent_msi_domain(void)
+{
+	struct irq_domain_info info = {
+		.fwnode		= irq_domain_alloc_named_fwnode("zpci_msi"),
+		.ops		= &zpci_msi_domain_ops
+	};
+	if (!info.fwnode) {
+		pr_err("Failed to allocate fwnode for MSI IRQ domain\n");
+		return -ENOMEM;
+	}
+
+	zpci_msi_parent_domain = msi_create_parent_irq_domain(&info, &zpci_msi_parent_ops);
+	if (!zpci_msi_parent_domain) {
+		irq_domain_free_fwnode(info.fwnode);
+		pr_err("Failed to create MSI IRQ domain\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+void zpci_set_msi_parent_domain(struct zpci_bus *zbus)
+{
+	dev_set_msi_domain(&zbus->bus->dev, zpci_msi_parent_domain);
+}
+
 static void __init cpu_enable_directed_irq(void *unused)
 {
 	union zpci_sic_iib iib = {{0}};
@@ -466,7 +535,7 @@ static int __init zpci_directed_irq_init(void)
 		 * is only done on the first vector.
 		 */
 		zpci_ibv[cpu] = airq_iv_create(cache_line_size() * BITS_PER_BYTE,
-					       AIRQ_IV_DATA |
+					       AIRQ_IV_PTR |
 					       AIRQ_IV_CACHELINE |
 					       (!cpu ? AIRQ_IV_ALLOC : 0), NULL);
 		if (!zpci_ibv[cpu])
@@ -511,6 +580,11 @@ int __init zpci_irq_init(void)
 	rc = register_adapter_interrupt(&zpci_airq);
 	if (rc)
 		goto out;
+
+	zpci_create_parent_msi_domain();
+	if (!zpci_msi_parent_domain)
+		goto out_airq;
+
 	/* Set summary to 1 to be called every time for the ISC. */
 	*zpci_airq.lsi_ptr = 1;
 
@@ -524,7 +598,7 @@ int __init zpci_irq_init(void)
 	}
 
 	if (rc)
-		goto out_airq;
+		goto out_msi_domain;
 
 	/*
 	 * Enable floating IRQs (with suppression after one IRQ). When using
@@ -533,6 +607,8 @@ int __init zpci_irq_init(void)
 	zpci_set_irq_ctrl(SIC_IRQ_MODE_SINGLE, PCI_ISC, &iib);
 
 	return 0;
+out_msi_domain:
+	irq_domain_remove(zpci_msi_parent_domain);
 out_airq:
 	unregister_adapter_interrupt(&zpci_airq);
 out:
@@ -549,6 +625,7 @@ void __init zpci_irq_exit(void)
 		}
 	}
 	kfree(zpci_ibv);
+	irq_domain_remove(zpci_msi_parent_domain);
 	if (zpci_sbv)
 		airq_iv_release(zpci_sbv);
 	unregister_adapter_interrupt(&zpci_airq);

-- 
2.48.1

Powered by blists - more mailing lists