[PATCH v5 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain API

[PATCH v5 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 v5:
- removed two lines of superfluous code
- Link to v4: https://lore.kernel.org/r/20251120-implement-msi-domain-v4-0-a01be58e158a@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     | 333 +++++++++++++++++++++++++++-----------------
 include/linux/irqdesc.h     |   6 +-
 kernel/irq/irqdesc.c        |   6 +-
 6 files changed, 233 insertions(+), 138 deletions(-)
---
base-commit: 82ef9f0fac73cca3e7d776b095b5a7de1b0b88fc
change-id: 20251104-implement-msi-domain-dc1ea014580e

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

[PATCH v5 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>
Reviewed-by: Farhan Ali <alifm@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 v5 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.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
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     | 333 +++++++++++++++++++++++++++-----------------
 4 files changed, 227 insertions(+), 132 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 778ce20d34046cad84dd4ef57cab5a662e5796d9..46ab67d607f0db7f5f108106172699a5eebfc8c8 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..b0be21ab56995e81f54339fc77167f5930182542 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 +297,217 @@ 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;
+	int i;
+
+	for (i = 0; i < nr_irqs; i++) {
+		d = irq_domain_get_irq_data(domain, virq + i);
+		hwirq = d->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 +544,7 @@ 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 v5 0/2] genirq: s390/pci: Migrate MSI interrupts to irqdomain API

[Niklas Schnelle]

On Fri, 2025-11-21 at 06:32 +0100, Tobias Schumacher wrote:
> 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>
> ---

@Heiko, @Vasily, @Alexander, from my point of view this series is ready
to be picked up for the s390 tree and would also benefit from time on
linux-next etc.

Thanks,
Niklas

Re: [PATCH v5 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Heiko Carstens]

On Fri, Nov 21, 2025 at 06:32:19AM +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:
...
> 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     | 333 +++++++++++++++++++++++++++-----------------
>  4 files changed, 227 insertions(+), 132 deletions(-)
...
>  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
>  };

C99 initializers are supposed to end with a comma. If new initializers would be
added with subsequent patches, this makes the patches smaller (adding the
extra "," to the existing line is just noise).

> -	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);
> -	}

Bodies of if-statements with more than one line are supposed to come with
brackets for readability reasons, like it used to be before your change.

Note that for new s390 code we mostly follow the coding style guideline as
described in Documentation/process/maintainer-tip.rst. Maybe it makes sense
to spend the effort to add an s390 specific variant of that document...

Anyway, I'll change your code accordingly when applying - no need for a
version.

Re: [PATCH v5 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Gerd Bayer]

Hi Tobias,

sorry for being late with my comments...

On Fri, 2025-11-21 at 06:32 +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.

This is no longer true with the per-PCI-domain irq domains! But you
encode the hwirq with the devfn within the PCI domain, instead.


> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
> Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
> 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     | 333 +++++++++++++++++++++++++++-----------------
>  4 files changed, 227 insertions(+), 132 deletions(-)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 778ce20d34046cad84dd4ef57cab5a662e5796d9..46ab67d607f0db7f5f108106172699a5eebfc8c8 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

Nit: There's precedence for both versions (above and below!) but I
personally would prefer to indent the pre-condition "if PCI" so it
stands out. Maybe that's a generic clean-up task for this arch-specific
file...

>  	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;
> +

If you shortened this to use the call to
zpci_create_parent_msi_domain() as predicate for "if" you could do
without the additional rc.

> 
>  	/*
>  	 * 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;

Or do you want to set rc to -EFAULT here, and return the "original" rc
in the error exits?

>  
>  	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..b0be21ab56995e81f54339fc77167f5930182542 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)


Any specific reason, why you removed zpci_clear_irq() indirecting to
airq vs. directed_irq - but kept zpci_set_irq()? Just saying this is
imbalanced now.

> +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;
>  

[... snip ...]

> 
> @@ -290,146 +297,217 @@ 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);


Please don't use GENMASK_U16. It is harder to read than any explicit
constant like 0x00FF, especially since its parameters contradict the
architecture's endianess.
But then, is this called anywhere?

> +}
> +
> +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;

These two failure clean-ups look a lot like
zpci_msi_teardown_directed/_floating() below. Could these be called
instead of duplicating the code?

>  		}
> +		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);
> +}
> +

[... snip ...]

No more findings at this point in time.
Thanks for your work!

Gerd

Re: [PATCH v5 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Heiko Carstens]

On Fri, Nov 21, 2025 at 02:27:38PM +0100, Gerd Bayer wrote:
> >  	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;
> 
> Or do you want to set rc to -EFAULT here, and return the "original" rc
> in the error exits?
> 
> >  
> >  	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;
> >  }

Oh, just realized this oddity with Gerd's reply: -EFAULT should _only_ be used
for page faults. Looks like this return code is not passed to user space, but
please change this to something more appropriate. E.g. -ENOMEM, or whatever
fits here.

Given that Gerd had quite a few more comments, please send a new version with
my comments also addressed :)

Re: [PATCH v5 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Tobias Schumacher]

On Fri Nov 21, 2025 at 3:03 PM CET, Heiko Carstens wrote:
> On Fri, Nov 21, 2025 at 02:27:38PM +0100, Gerd Bayer wrote:
>> >  	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;
>> 
>> Or do you want to set rc to -EFAULT here, and return the "original" rc
>> in the error exits?
>> 
>> >  
>> >  	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;
>> >  }
>
> Oh, just realized this oddity with Gerd's reply: -EFAULT should _only_ be used
> for page faults. Looks like this return code is not passed to user space, but
> please change this to something more appropriate. E.g. -ENOMEM, or whatever
> fits here.
>
> Given that Gerd had quite a few more comments, please send a new version with
> my comments also addressed :)

Sure, will do

Thanks,
Tobias

Re: [PATCH v5 2/2] s390/pci: Migrate s390 IRQ logic to IRQ domain API

[Tobias Schumacher]

On Fri Nov 21, 2025 at 2:27 PM CET, Gerd Bayer wrote:
> Hi Tobias,
>
> sorry for being late with my comments...
>
> On Fri, 2025-11-21 at 06:32 +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.
>
> This is no longer true with the per-PCI-domain irq domains! But you
> encode the hwirq with the devfn within the PCI domain, instead.

Correct, will fix that.

>> Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
>> Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
>> 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     | 333 +++++++++++++++++++++++++++-----------------
>>  4 files changed, 227 insertions(+), 132 deletions(-)
>> 
>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>> index 778ce20d34046cad84dd4ef57cab5a662e5796d9..46ab67d607f0db7f5f108106172699a5eebfc8c8 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
>
> Nit: There's precedence for both versions (above and below!) but I
> personally would prefer to indent the pre-condition "if PCI" so it
> stands out. Maybe that's a generic clean-up task for this arch-specific
> file...

Since at least the 'if PCI' preconditions are indented in this file,
I'll also do it for this line. 

>> @@ -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;
>> +
>
> If you shortened this to use the call to
> zpci_create_parent_msi_domain() as predicate for "if" you could do
> without the additional rc.

Will do.

>>  	/*
>>  	 * 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;
>
> Or do you want to set rc to -EFAULT here, and return the "original" rc
> in the error exits?

As Heiko mentioned, -EFAULT shouldn't be returned anyways I'd change it
to -ENOMEM for all error cases.

--- snip ---

>> diff --git a/arch/s390/pci/pci_irq.c b/arch/s390/pci/pci_irq.c
>> index e73be96ce5fe6473fc193d65b8f0ff635d6a98ba..b0be21ab56995e81f54339fc77167f5930182542 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)
>
>
> Any specific reason, why you removed zpci_clear_irq() indirecting to
> airq vs. directed_irq - but kept zpci_set_irq()? Just saying this is
> imbalanced now.

I removed it because it was only required in zpci_msi_teardown(), which
already has the distinction between directed and floating IRQs. So
having a separate zpci_clear_irq() seemed redundant. 

--- snip ---

>> +static inline u16 zpci_decode_hwirq_msi_index(irq_hw_number_t irq)
>> +{
>> +	return irq & GENMASK_U16(15, 0);
>
>
> Please don't use GENMASK_U16. It is harder to read than any explicit
> constant like 0x00FF, especially since its parameters contradict the
> architecture's endianess.
> But then, is this called anywhere?

Right, it's not used anymore, I'll remove it completely.

--- snip ---

>> +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;
>
> These two failure clean-ups look a lot like
> zpci_msi_teardown_directed/_floating() below. Could these be called
> instead of duplicating the code?

Yes they are similar, only that zpci_msi_teardown_directed/_floating()
also call zpci_clear_directed_irq()/zpci_clear_airq(), respectively.
Considering your other comment above, it might be cleaner to add
zpci_clear_irq() again, call this directly from zpci_msi_teardown() and
then use zpci_msi_teardown_directed/_floating() here as suggested.

Thanks,
Tobias