[PATCH v4 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain API

[PATCH v4 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain API

[Tobias Schumacher]

This patch series reworks the PCIe interrupt handling on s390 by
migrating it to use a proper MSI parent domain. Introducing a dedicated
MSI domain hierarchy aligns s390 PCIe support with the generic Linux IRQ
domain model. Currently s390 is one of the last architectures still using
the legacy API.

The migration splits the existing code in the legacy functions
arch_setup_msi_irqs() and arch_teardown_msi_irqs() into different
callbacks of the newly created MSI parent domain:

- zpci_msi_prepare(): prepare the allocation of per-device MSI IRQs.
      will be called once for each device before allocating individual
      IRQs and sets up for example the adapter aisb and aibv.
- zpci_msi_teardown(): reverts the effects of zpci_msi_prepare() and is
      called after all MSI IRQs are freed.
- zpci_msi_domain_alloc(): the allocation function for interrupts
- zpci_msi_domain_free(): revert the effects of zpci_msi_domain_alloc()
- zpci_compose_msi_msg(): create the MSI message to be written into the
      corresponding PCI config space.

* Patch 1 fixes an inconsistency in the irqdomain API. Internally, hw
  irqs are represented by an unsigned long int (irq_hw_number_t) while
  the external API in some cases takes an unsigned int as parameter.
  This fix was required in V2 of the patchset. Due to conceptual changes
  in patch 2 it is not required anymore for s390, but still seems
  sensible.
* Patch 2 implements IRQ domains for s390 PCI

Since patch 1 changes common APIs, some build tests were done for x86_64
and arm64. 

Signed-off-by: Tobias Schumacher <ts@linux.ibm.com>
---
Changes in v4:
- remove flag MSI_FLAG_PCI_MSI_MASK_PARENT and mask/unmask callbacks
- use goto statements in zpci_bus_create_pci_bus()
- Link to v3: https://lore.kernel.org/r/20251118-implement-msi-domain-v3-0-6fe8feb2a93f@linux.ibm.com

Changes in v3:
- implement one MSI parent domain per PCI domain to further align the
  implementation with other architectures.
- Link to v2: https://lore.kernel.org/r/20251117-implement-msi-domain-v2-0-a110ea0721fe@linux.ibm.com

Changes in v2:
- fix directed interrupt setup and handling
- add flag MSI_FLAG_NO_AFFINITY in case of floating interrupts
- style adjustments according to review comments
- Link to v1: https://lore.kernel.org/r/20251112-implement-msi-domain-v1-0-103dd123de14@linux.ibm.com

---
Tobias Schumacher (2):
      genirq: Change hwirq parameter to irq_hw_number_t
      s390/pci: Migrate s390 IRQ logic to IRQ domain API

 arch/s390/Kconfig           |   1 +
 arch/s390/include/asm/pci.h |   4 +
 arch/s390/pci/pci_bus.c     |  21 ++-
 arch/s390/pci/pci_irq.c     | 335 +++++++++++++++++++++++++++-----------------
 include/linux/irqdesc.h     |   6 +-
 kernel/irq/irqdesc.c        |   6 +-
 6 files changed, 235 insertions(+), 138 deletions(-)
---
base-commit: 882489402b556fa6d916cba86051276fcc9a8953
change-id: 20251104-implement-msi-domain-dc1ea014580e

Best regards,
-- 
Tobias Schumacher <ts@linux.ibm.com>

[PATCH v4 1/2] genirq: Change hwirq parameter to irq_hw_number_t

[Tobias Schumacher]

The irqdomain implementation internally represents hardware IRQs as
irq_hw_number_t, which is defined as unsigned long int. When providing
an irq_hw_number_t to the generic_handle_domain() functions that expect
and unsigned int hwirq, this can lead to a loss of information. Change
the hwirq parameter to irq_hw_number_t to support the full range of
hwirqs.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Tobias Schumacher <ts@linux.ibm.com>
---
 include/linux/irqdesc.h | 6 +++---
 kernel/irq/irqdesc.c    | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index fd091c35d5721eee37a2fd3d5526559671d5048d..03b63aea73bb21ae1456910afa534d60f9cfa94d 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -183,9 +183,9 @@ int generic_handle_irq_safe(unsigned int irq);
  * and handle the result interrupt number. Return -EINVAL if
  * conversion failed.
  */
-int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq);
-int generic_handle_domain_irq_safe(struct irq_domain *domain, unsigned int hwirq);
-int generic_handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq);
+int generic_handle_domain_irq(struct irq_domain *domain, irq_hw_number_t hwirq);
+int generic_handle_domain_irq_safe(struct irq_domain *domain, irq_hw_number_t hwirq);
+int generic_handle_domain_nmi(struct irq_domain *domain, irq_hw_number_t hwirq);
 #endif
 
 /* Test to see if a driver has successfully requested an irq */
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index db714d3014b5f7b62403ea04b80331ec6b1dc642..0cd3198496bc0766c81c353c3ff80ea184793d6a 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -720,7 +720,7 @@ EXPORT_SYMBOL_GPL(generic_handle_irq_safe);
  * 		This function must be called from an IRQ context with irq regs
  * 		initialized.
  */
-int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq)
+int generic_handle_domain_irq(struct irq_domain *domain, irq_hw_number_t hwirq)
 {
 	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
 }
@@ -738,7 +738,7 @@ EXPORT_SYMBOL_GPL(generic_handle_domain_irq);
  * context). If the interrupt is marked as 'enforce IRQ-context only' then
  * the function must be invoked from hard interrupt context.
  */
-int generic_handle_domain_irq_safe(struct irq_domain *domain, unsigned int hwirq)
+int generic_handle_domain_irq_safe(struct irq_domain *domain, irq_hw_number_t hwirq)
 {
 	unsigned long flags;
 	int ret;
@@ -761,7 +761,7 @@ EXPORT_SYMBOL_GPL(generic_handle_domain_irq_safe);
  * 		This function must be called from an NMI context with irq regs
  * 		initialized.
  **/
-int generic_handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq)
+int generic_handle_domain_nmi(struct irq_domain *domain, irq_hw_number_t hwirq)
 {
 	WARN_ON_ONCE(!in_nmi());
 	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));

-- 
2.48.1

[PATCH v4 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Tobias Schumacher]

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 each PCI domain. When a PCI
device sets up MSI or MSI-X IRQs, the library creates a per-device IRQ
domain for this device, which is 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
  called 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@linux.ibm.com>
---
 arch/s390/Kconfig           |   1 +
 arch/s390/include/asm/pci.h |   4 +
 arch/s390/pci/pci_bus.c     |  21 ++-
 arch/s390/pci/pci_irq.c     | 335 +++++++++++++++++++++++++++-----------------
 4 files changed, 229 insertions(+), 132 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index df22b10d91415e1ed183cc8add9ad0ac4293c50e..48cd6a12bd04dfe4dd61ecc79d3401ba685c51bb 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..60abc84cf14fe6fb1ee149df688eea94f0983ed0 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -5,6 +5,7 @@
 #include <linux/pci.h>
 #include <linux/mutex.h>
 #include <linux/iommu.h>
+#include <linux/irqdomain.h>
 #include <linux/pci_hotplug.h>
 #include <asm/pci_clp.h>
 #include <asm/pci_debug.h>
@@ -109,6 +110,7 @@ struct zpci_bus {
 	struct list_head	resources;
 	struct list_head	bus_next;
 	struct resource		bus_resource;
+	struct irq_domain       *msi_parent_domain;
 	int			topo;		/* TID if topo_is_tid, PCHID otherwise */
 	int			domain_nr;
 	u8			multifunction	: 1;
@@ -310,6 +312,8 @@ int zpci_dma_exit_device(struct zpci_dev *zdev);
 /* IRQ */
 int __init zpci_irq_init(void);
 void __init zpci_irq_exit(void);
+int zpci_create_parent_msi_domain(struct zpci_bus *zbus);
+void zpci_remove_parent_msi_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..9da261b600df805ef76f3331975ac8fce6178908 100644
--- a/arch/s390/pci/pci_bus.c
+++ b/arch/s390/pci/pci_bus.c
@@ -15,6 +15,7 @@
 #include <linux/err.h>
 #include <linux/delay.h>
 #include <linux/seq_file.h>
+#include <linux/irqdomain.h>
 #include <linux/jump_label.h>
 #include <linux/pci.h>
 #include <linux/printk.h>
@@ -189,7 +190,7 @@ static bool zpci_bus_is_multifunction_root(struct zpci_dev *zdev)
 static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *fr, struct pci_ops *ops)
 {
 	struct pci_bus *bus;
-	int domain;
+	int domain, rc;
 
 	domain = zpci_alloc_domain((u16)fr->uid);
 	if (domain < 0)
@@ -199,19 +200,28 @@ static int zpci_bus_create_pci_bus(struct zpci_bus *zbus, struct zpci_dev *fr, s
 	zbus->multifunction = zpci_bus_is_multifunction_root(fr);
 	zbus->max_bus_speed = fr->max_bus_speed;
 
+	rc = zpci_create_parent_msi_domain(zbus);
+	if (rc)
+		goto out_free_domain;
+
 	/*
 	 * Note that the zbus->resources are taken over and zbus->resources
 	 * is empty after a successful call
 	 */
 	bus = pci_create_root_bus(NULL, ZPCI_BUS_NR, ops, zbus, &zbus->resources);
-	if (!bus) {
-		zpci_free_domain(zbus->domain_nr);
-		return -EFAULT;
-	}
+	if (!bus)
+		goto out_remove_msi_domain;
 
 	zbus->bus = bus;
+	dev_set_msi_domain(&zbus->bus->dev, zbus->msi_parent_domain);
 
 	return 0;
+
+out_remove_msi_domain:
+	zpci_remove_parent_msi_domain(zbus);
+out_free_domain:
+	zpci_free_domain(zbus->domain_nr);
+	return -EFAULT;
 }
 
 static void zpci_bus_release(struct kref *kref)
@@ -232,6 +242,7 @@ static void zpci_bus_release(struct kref *kref)
 	mutex_lock(&zbus_list_lock);
 	list_del(&zbus->bus_next);
 	mutex_unlock(&zbus_list_lock);
+	zpci_remove_parent_msi_domain(zbus);
 	kfree(zbus);
 }
 
diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
index e73be96ce5fe6473fc193d65b8f0ff635d6a98ba..f67c50632a796b0aa438ac9464da53acc0296218 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>
@@ -110,43 +111,41 @@ static int zpci_set_irq(struct zpci_dev *zdev)
 	return rc;
 }
 
-/* Clear adapter interruptions */
-static int zpci_clear_irq(struct zpci_dev *zdev)
+static int zpci_set_irq_affinity(struct irq_data *data, const struct cpumask *dest,
+				 bool force)
 {
-	int rc;
-
-	if (irq_delivery == DIRECTED)
-		rc = zpci_clear_directed_irq(zdev);
-	else
-		rc = zpci_clear_airq(zdev);
-
-	return rc;
+	irq_data_update_affinity(data, dest);
+	return IRQ_SET_MASK_OK;
 }
 
-static int zpci_set_irq_affinity(struct irq_data *data, const struct cpumask *dest,
-				 bool force)
+static void zpci_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 {
-	struct msi_desc *entry = irq_data_get_msi_desc(data);
-	struct msi_msg msg = entry->msg;
-	int cpu_addr = smp_cpu_get_cpu_address(cpumask_first(dest));
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct zpci_dev *zdev = to_zpci_dev(desc->dev);
 
-	msg.address_lo &= 0xff0000ff;
-	msg.address_lo |= (cpu_addr << 8);
-	pci_write_msi_msg(data->irq, &msg);
+	if (irq_delivery == DIRECTED) {
+		int cpu = cpumask_first(irq_data_get_affinity_mask(data));
 
-	return IRQ_SET_MASK_OK;
+		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 & 0xffffffff;
 }
 
 static struct irq_chip zpci_irq_chip = {
 	.name = "PCI-MSI",
-	.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}};
+	struct irq_domain *msi_domain;
+	irq_hw_number_t hwirq;
 	unsigned long bit;
 	int irqs_on = 0;
 
@@ -164,7 +163,9 @@ 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_data(dibv, bit);
+		msi_domain = (struct irq_domain *)airq_iv_get_ptr(dibv, bit);
+		generic_handle_domain_irq(msi_domain, hwirq);
 	}
 }
 
@@ -229,6 +230,8 @@ static void zpci_floating_irq_handler(struct airq_struct *airq,
 				      struct tpi_info *tpi_info)
 {
 	union zpci_sic_iib iib = {{0}};
+	struct irq_domain *msi_domain;
+	irq_hw_number_t hwirq;
 	unsigned long si, ai;
 	struct airq_iv *aibv;
 	int irqs_on = 0;
@@ -256,7 +259,9 @@ 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_data(aibv, ai);
+			msi_domain = (struct irq_domain *)airq_iv_get_ptr(aibv, ai);
+			generic_handle_domain_irq(msi_domain, hwirq);
 			airq_iv_unlock(aibv, ai);
 		}
 	}
@@ -278,7 +283,9 @@ 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_DATA | AIRQ_IV_BITLOCK,
+					    NULL);
 		if (!zdev->aibv)
 			return -ENOMEM;
 
@@ -290,146 +297,219 @@ 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)
+bool arch_restore_msi_irqs(struct pci_dev *pdev)
 {
-	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;
 
-	zdev->aisb = -1UL;
-	zdev->msi_first_bit = -1U;
+	zpci_set_irq(zdev);
+	return true;
+}
+
+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 devfn to
+ * identify the device and the msi_index to identify the IRQ within that device.
+ */
+static inline u32 zpci_encode_hwirq(u8 devfn, u16 msi_index)
+{
+	return (devfn << 16) | msi_index;
+}
+
+static inline u16 zpci_decode_hwirq_msi_index(irq_hw_number_t irq)
+{
+	return irq & GENMASK_U16(15, 0);
+}
+
+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) {
-		pr_info("%s requested %d irqs, allocate system limit of %d",
+	if (msi_vecs < nvec)
+		pr_info("%s requested %d IRQs, allocate system limit of %d\n",
 			pci_name(pdev), nvec, zdev->max_msi);
-	}
 
 	rc = __alloc_airq(zdev, msi_vecs, &bit);
-	if (rc < 0)
+	if (rc) {
+		pr_err("Allocating adapter IRQs 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);
+	zdev->msi_first_bit = bit;
+	zdev->msi_nr_irqs = msi_vecs;
+	rc = zpci_set_irq(zdev);
+	if (rc) {
+		pr_err("Registering adapter IRQs for %s failed\n",
+		       pci_name(pdev));
+		if (irq_delivery == DIRECTED) {
+			airq_iv_free(zpci_ibv[0], zdev->msi_first_bit, msi_vecs);
+		} else {
+			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;
+		return rc;
+	}
 
-		msg.data = hwirq - bit;
-		if (irq_delivery == DIRECTED) {
-			if (msi->affinity)
-				cpu = cpumask_first(&msi->affinity->mask);
-			else
-				cpu = 0;
-			cpu_addr = smp_cpu_get_cpu_address(cpu);
+	return 0;
+}
+
+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;
+}
+
+static void zpci_msi_teardown_floating(struct zpci_dev *zdev)
+{
+	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;
+}
 
-			msg.address_lo = zdev->msi_addr & 0xff0000ff;
-			msg.address_lo |= (cpu_addr << 8);
+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);
+	struct zpci_bus *zbus = zdev->zbus;
+	unsigned int cpu, hwirq;
+	unsigned long bit;
+	int i;
+
+	bit = zdev->msi_first_bit + desc->msi_index;
+	hwirq = zpci_encode_hwirq(zdev->devfn, 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);
+
+		if (irq_delivery == DIRECTED) {
 			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_set_ptr(zpci_ibv[cpu], bit + i,
+						(unsigned long)zbus->msi_parent_domain);
+				airq_iv_set_data(zpci_ibv[cpu], bit + i, hwirq + i);
 			}
 		} 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);
+			airq_iv_set_ptr(zdev->aibv, bit + i,
+					(unsigned long)zbus->msi_parent_domain);
+			airq_iv_set_data(zdev->aibv, bit + i, hwirq + i);
 		}
-		msg.address_hi = zdev->msi_addr >> 32;
-		pci_write_msi_msg(irq, &msg);
-		hwirq += irqs_per_msi;
 	}
 
-	zdev->msi_first_bit = bit;
-	zdev->msi_nr_irqs = hwirq - bit;
+	return 0;
+}
 
-	rc = zpci_set_irq(zdev);
-	if (rc)
-		return rc;
+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);
+	}
+}
+
+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)
+{
+	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;
 
-	return (zdev->msi_nr_irqs == nvec) ? 0 : zdev->msi_nr_irqs;
+	return true;
 }
 
-void arch_teardown_msi_irqs(struct pci_dev *pdev)
+static 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,
+	.init_dev_msi_info = zpci_init_dev_msi_info
+};
+
+int zpci_create_parent_msi_domain(struct zpci_bus *zbus)
 {
-	struct zpci_dev *zdev = to_zpci(pdev);
-	struct msi_desc *msi;
-	unsigned int i;
-	int rc;
+	char fwnode_name[18];
 
-	/* Disable interrupts */
-	rc = zpci_clear_irq(zdev);
-	if (rc)
-		return;
+	sprintf(fwnode_name, "ZPCI_MSI_DOM_%04x", zbus->domain_nr);
+	struct irq_domain_info info = {
+		.fwnode		= irq_domain_alloc_named_fwnode(fwnode_name),
+		.ops		= &zpci_msi_domain_ops
+	};
 
-	/* 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);
-		}
-		msi->msg.address_lo = 0;
-		msi->msg.address_hi = 0;
-		msi->msg.data = 0;
-		msi->irq = 0;
+	if (!info.fwnode) {
+		pr_err("Failed to allocate fwnode for MSI IRQ domain\n");
+		return -ENOMEM;
 	}
 
-	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;
+	if (irq_delivery == FLOATING)
+		zpci_msi_parent_ops.required_flags |= MSI_FLAG_NO_AFFINITY;
+	zbus->msi_parent_domain = msi_create_parent_irq_domain(&info, &zpci_msi_parent_ops);
+	if (!zbus->msi_parent_domain) {
+		irq_domain_free_fwnode(info.fwnode);
+		pr_err("Failed to create MSI IRQ domain\n");
+		return -ENOMEM;
 	}
 
-	if ((irq_delivery == DIRECTED) && zdev->msi_first_bit != -1U)
-		airq_iv_free(zpci_ibv[0], zdev->msi_first_bit, zdev->msi_nr_irqs);
+	return 0;
 }
 
-bool arch_restore_msi_irqs(struct pci_dev *pdev)
+void zpci_remove_parent_msi_domain(struct zpci_bus *zbus)
 {
-	struct zpci_dev *zdev = to_zpci(pdev);
+	struct fwnode_handle *fn;
 
-	zpci_set_irq(zdev);
-	return true;
+	fn = zbus->msi_parent_domain->fwnode;
+	irq_domain_remove(zbus->msi_parent_domain);
+	irq_domain_free_fwnode(fn);
 }
 
-static struct airq_struct zpci_airq = {
-	.handler = zpci_floating_irq_handler,
-	.isc = PCI_ISC,
-};
-
 static void __init cpu_enable_directed_irq(void *unused)
 {
 	union zpci_sic_iib iib = {{0}};
@@ -466,6 +546,7 @@ 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_PTR |
 					       AIRQ_IV_DATA |
 					       AIRQ_IV_CACHELINE |
 					       (!cpu ? AIRQ_IV_ALLOC : 0), NULL);

-- 
2.48.1

Re: [PATCH v4 1/2] genirq: Change hwirq parameter to irq_hw_number_t

[Farhan Ali]

On 11/20/2025 2:27 AM, Tobias Schumacher wrote:
> The irqdomain implementation internally represents hardware IRQs as
> irq_hw_number_t, which is defined as unsigned long int. When providing
> an irq_hw_number_t to the generic_handle_domain() functions that expect
> and unsigned int hwirq, this can lead to a loss of information. Change
> the hwirq parameter to irq_hw_number_t to support the full range of
> hwirqs.
>
> Reviewed-by: Thomas Gleixner<tglx@linutronix.de>
> Reviewed-by: Niklas Schnelle<schnelle@linux.ibm.com>
> Signed-off-by: Tobias Schumacher<ts@linux.ibm.com>
> ---
>   include/linux/irqdesc.h | 6 +++---
>   kernel/irq/irqdesc.c    | 6 +++---
>   2 files changed, 6 insertions(+), 6 deletions(-)

Reviewed-by: Farhan Ali <alifm@linux.ibm.com>

Re: [PATCH v4 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Farhan Ali]

On 11/20/2025 2:27 AM, Tobias Schumacher wrote:
> 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 each PCI domain. When a PCI
> device sets up MSI or MSI-X IRQs, the library creates a per-device IRQ
> domain for this device, which is 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
>    called 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@linux.ibm.com>
> ---
>   arch/s390/Kconfig           |   1 +
>   arch/s390/include/asm/pci.h |   4 +
>   arch/s390/pci/pci_bus.c     |  21 ++-
>   arch/s390/pci/pci_irq.c     | 335 +++++++++++++++++++++++++++-----------------
>   4 files changed, 229 insertions(+), 132 deletions(-)

Thanks for making the changes!

Reviewed-by: Farhan Ali <alifm@linux.ibm.com>

Re: [PATCH v4 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Niklas Schnelle]

On Thu, 2025-11-20 at 11:27 +0100, Tobias Schumacher wrote:
> 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 each PCI domain. When a PCI
> device sets up MSI or MSI-X IRQs, the library creates a per-device IRQ
> domain for this device, which is 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
>   called 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@linux.ibm.com>
> ---
>  arch/s390/Kconfig           |   1 +
>  arch/s390/include/asm/pci.h |   4 +
>  arch/s390/pci/pci_bus.c     |  21 ++-
>  arch/s390/pci/pci_irq.c     | 335 +++++++++++++++++++++++++++-----------------
>  4 files changed, 229 insertions(+), 132 deletions(-)
--- snip ---
> +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);

The msi_index isn't used or needed so the above two lines can be
removed together with their respective variables.

> +		irq_domain_reset_irq_data(d);
> +	}
> +}
> +
--- snip ---

Apart from the above trivial superfluous code this looks even better
than v3 now. Makes the hwirq encoding smaller and more dense which I
think is also nice and as previously discussed the IRQ domain per
(virtual) PCI domain seems like a good fit. Thanks again for the great
work.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>