[PATCH v7 0/2] PCI: hv: Hyper-V vPCI for arm64

[PATCH v7 0/2] PCI: hv: Hyper-V vPCI for arm64

[Sunil Muthuswamy]

From: Sunil Muthuswamy <sunilmut@microsoft.com>

Current Hyper-V vPCI code only compiles and works for x86. There are some
hardcoded assumptions about the architectural IRQ chip and other arch
defines.

Add support for Hyper-V vPCI for arm64 by first breaking the current hard
coded dependency using a set of new interfaces and implementing those for
x86 first. That is in the first patch. The second patch adds support for
Hyper-V vPCI for arm64 by implementing the above mentioned interfaces. That
is done by introducing a Hyper-V vPCI specific MSI IRQ domain & chip for
allocating SPI vectors.

changes in v1 -> v2:
 - Moved the irqchip implementation to drivers/pci as suggested
   by Marc Zyngier
 - Addressed Multi-MSI handling issues identified by Marc Zyngier
 - Addressed lock/synchronization primitive as suggested by Marc
   Zyngier
 - Addressed other code feedback from Marc Zyngier

changes in v2 -> v3:
 - Addressed comments from Bjorn Helgaas about patch formatting and
   verbiage
 - Using 'git send-email' to ensure that the patch series is correctly
   threaded. Feedback by Bjorn Helgaas
 - Fixed Hyper-V vPCI build break for module build, reported by Boqun Feng

changes in v3 -> v4:
 - Removed the separate file for IRQ chip that was there in previous
   iterations and moved the IRQ chip implementation to pci-hyperv.c.
   Feedback by Michael Kelley and Marc Zyngier.
 - Addressed various comments from Marc Zyngier about structuring and
   layout.
 - Addressed comment from Marc Zyngier about IRQ affinity and other
   miscellaneous comments.

changes in v4 -> v5:
 - Fixed an issue with picking the right cpu for irq affinity, identified
   by Marc Zyngier.

changes in v5 -> v6:
 - Minor comment updates suggested by Michael Kelley.

changes in v6 -> v7:
 - Addressed feedback from Marc Zyngier about IRQ cleanup in the error path
   and explicitly setting the IRQ trigger type.
 - Address feedback from Bjorn Helgaas about subject line format.

Sunil Muthuswamy (2):
  PCI: hv: Make the code arch neutral by adding arch specific interfaces
  PCI: hv: Add arm64 Hyper-V vPCI support

 arch/arm64/include/asm/hyperv-tlfs.h |   9 +
 arch/x86/include/asm/hyperv-tlfs.h   |  33 +++
 arch/x86/include/asm/mshyperv.h      |   7 -
 drivers/pci/Kconfig                  |   2 +-
 drivers/pci/controller/Kconfig       |   2 +-
 drivers/pci/controller/pci-hyperv.c  | 318 ++++++++++++++++++++++++---
 include/asm-generic/hyperv-tlfs.h    |  33 ---
 7 files changed, 337 insertions(+), 67 deletions(-)


base-commit: fa55b7dcdc43c1aa1ba12bca9d2dd4318c2a0dbf
-- 
2.25.1

[PATCH v7 1/2] PCI: hv: Make the code arch neutral by adding arch specific interfaces

[Sunil Muthuswamy]

From: Sunil Muthuswamy <sunilmut@microsoft.com>

Encapsulate arch dependencies in Hyper-V vPCI through a set of
arch-dependent interfaces. Adding these arch specific interfaces will
allow for an implementation for other architectures, such as arm64.

There are no functional changes expected from this patch.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
---
In v2, v3, v4, v5, v6 & v7:
 Changes are described in the cover letter. No changes from v4 -> v5 or
 v6 -> v7.

 arch/x86/include/asm/hyperv-tlfs.h  | 33 ++++++++++++
 arch/x86/include/asm/mshyperv.h     |  7 ---
 drivers/pci/controller/pci-hyperv.c | 79 ++++++++++++++++++++---------
 include/asm-generic/hyperv-tlfs.h   | 33 ------------
 4 files changed, 87 insertions(+), 65 deletions(-)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 381e88122a5f..0a9407dc0859 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -602,6 +602,39 @@ enum hv_interrupt_type {
 	HV_X64_INTERRUPT_TYPE_MAXIMUM           = 0x000A,
 };
 
+union hv_msi_address_register {
+	u32 as_uint32;
+	struct {
+		u32 reserved1:2;
+		u32 destination_mode:1;
+		u32 redirection_hint:1;
+		u32 reserved2:8;
+		u32 destination_id:8;
+		u32 msi_base:12;
+	};
+} __packed;
+
+union hv_msi_data_register {
+	u32 as_uint32;
+	struct {
+		u32 vector:8;
+		u32 delivery_mode:3;
+		u32 reserved1:3;
+		u32 level_assert:1;
+		u32 trigger_mode:1;
+		u32 reserved2:16;
+	};
+} __packed;
+
+/* HvRetargetDeviceInterrupt hypercall */
+union hv_msi_entry {
+	u64 as_uint64;
+	struct {
+		union hv_msi_address_register address;
+		union hv_msi_data_register data;
+	} __packed;
+};
+
 #include <asm-generic/hyperv-tlfs.h>
 
 #endif
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index da3972fe5a7a..a1c3dceff8eb 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -169,13 +169,6 @@ bool hv_vcpu_is_preempted(int vcpu);
 static inline void hv_apic_init(void) {}
 #endif
 
-static inline void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
-					      struct msi_desc *msi_desc)
-{
-	msi_entry->address.as_uint32 = msi_desc->msg.address_lo;
-	msi_entry->data.as_uint32 = msi_desc->msg.data;
-}
-
 struct irq_domain *hv_create_pci_msi_domain(void);
 
 int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 6733cb14e775..ead7d6cb6bf1 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -43,9 +43,6 @@
 #include <linux/pci-ecam.h>
 #include <linux/delay.h>
 #include <linux/semaphore.h>
-#include <linux/irqdomain.h>
-#include <asm/irqdomain.h>
-#include <asm/apic.h>
 #include <linux/irq.h>
 #include <linux/msi.h>
 #include <linux/hyperv.h>
@@ -583,6 +580,42 @@ struct hv_pci_compl {
 
 static void hv_pci_onchannelcallback(void *context);
 
+#ifdef CONFIG_X86
+#define DELIVERY_MODE	APIC_DELIVERY_MODE_FIXED
+#define FLOW_HANDLER	handle_edge_irq
+#define FLOW_NAME	"edge"
+
+static int hv_pci_irqchip_init(void)
+{
+	return 0;
+}
+
+static struct irq_domain *hv_pci_get_root_domain(void)
+{
+	return x86_vector_domain;
+}
+
+static unsigned int hv_msi_get_int_vector(struct irq_data *data)
+{
+	struct irq_cfg *cfg = irqd_cfg(data);
+
+	return cfg->vector;
+}
+
+static void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
+				       struct msi_desc *msi_desc)
+{
+	msi_entry->address.as_uint32 = msi_desc->msg.address_lo;
+	msi_entry->data.as_uint32 = msi_desc->msg.data;
+}
+
+static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
+			  int nvec, msi_alloc_info_t *info)
+{
+	return pci_msi_prepare(domain, dev, nvec, info);
+}
+#endif /* CONFIG_X86 */
+
 /**
  * hv_pci_generic_compl() - Invoked for a completion packet
  * @context:		Set up by the sender of the packet.
@@ -1191,14 +1224,6 @@ static void hv_msi_free(struct irq_domain *domain, struct msi_domain_info *info,
 	put_pcichild(hpdev);
 }
 
-static int hv_set_affinity(struct irq_data *data, const struct cpumask *dest,
-			   bool force)
-{
-	struct irq_data *parent = data->parent_data;
-
-	return parent->chip->irq_set_affinity(parent, dest, force);
-}
-
 static void hv_irq_mask(struct irq_data *data)
 {
 	pci_msi_mask_irq(data);
@@ -1217,7 +1242,6 @@ static void hv_irq_mask(struct irq_data *data)
 static void hv_irq_unmask(struct irq_data *data)
 {
 	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
-	struct irq_cfg *cfg = irqd_cfg(data);
 	struct hv_retarget_device_interrupt *params;
 	struct hv_pcibus_device *hbus;
 	struct cpumask *dest;
@@ -1246,7 +1270,7 @@ static void hv_irq_unmask(struct irq_data *data)
 			   (hbus->hdev->dev_instance.b[7] << 8) |
 			   (hbus->hdev->dev_instance.b[6] & 0xf8) |
 			   PCI_FUNC(pdev->devfn);
-	params->int_target.vector = cfg->vector;
+	params->int_target.vector = hv_msi_get_int_vector(data);
 
 	/*
 	 * Honoring apic->delivery_mode set to APIC_DELIVERY_MODE_FIXED by
@@ -1347,7 +1371,7 @@ static u32 hv_compose_msi_req_v1(
 	int_pkt->wslot.slot = slot;
 	int_pkt->int_desc.vector = vector;
 	int_pkt->int_desc.vector_count = 1;
-	int_pkt->int_desc.delivery_mode = APIC_DELIVERY_MODE_FIXED;
+	int_pkt->int_desc.delivery_mode = DELIVERY_MODE;
 
 	/*
 	 * Create MSI w/ dummy vCPU set, overwritten by subsequent retarget in
@@ -1377,7 +1401,7 @@ static u32 hv_compose_msi_req_v2(
 	int_pkt->wslot.slot = slot;
 	int_pkt->int_desc.vector = vector;
 	int_pkt->int_desc.vector_count = 1;
-	int_pkt->int_desc.delivery_mode = APIC_DELIVERY_MODE_FIXED;
+	int_pkt->int_desc.delivery_mode = DELIVERY_MODE;
 	cpu = hv_compose_msi_req_get_cpu(affinity);
 	int_pkt->int_desc.processor_array[0] =
 		hv_cpu_number_to_vp_number(cpu);
@@ -1397,7 +1421,7 @@ static u32 hv_compose_msi_req_v3(
 	int_pkt->int_desc.vector = vector;
 	int_pkt->int_desc.reserved = 0;
 	int_pkt->int_desc.vector_count = 1;
-	int_pkt->int_desc.delivery_mode = APIC_DELIVERY_MODE_FIXED;
+	int_pkt->int_desc.delivery_mode = DELIVERY_MODE;
 	cpu = hv_compose_msi_req_get_cpu(affinity);
 	int_pkt->int_desc.processor_array[0] =
 		hv_cpu_number_to_vp_number(cpu);
@@ -1419,7 +1443,6 @@ static u32 hv_compose_msi_req_v3(
  */
 static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 {
-	struct irq_cfg *cfg = irqd_cfg(data);
 	struct hv_pcibus_device *hbus;
 	struct vmbus_channel *channel;
 	struct hv_pci_dev *hpdev;
@@ -1470,7 +1493,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
 					dest,
 					hpdev->desc.win_slot.slot,
-					cfg->vector);
+					hv_msi_get_int_vector(data));
 		break;
 
 	case PCI_PROTOCOL_VERSION_1_2:
@@ -1478,14 +1501,14 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		size = hv_compose_msi_req_v2(&ctxt.int_pkts.v2,
 					dest,
 					hpdev->desc.win_slot.slot,
-					cfg->vector);
+					hv_msi_get_int_vector(data));
 		break;
 
 	case PCI_PROTOCOL_VERSION_1_4:
 		size = hv_compose_msi_req_v3(&ctxt.int_pkts.v3,
 					dest,
 					hpdev->desc.win_slot.slot,
-					cfg->vector);
+					hv_msi_get_int_vector(data));
 		break;
 
 	default:
@@ -1594,14 +1617,14 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 static struct irq_chip hv_msi_irq_chip = {
 	.name			= "Hyper-V PCIe MSI",
 	.irq_compose_msi_msg	= hv_compose_msi_msg,
-	.irq_set_affinity	= hv_set_affinity,
+	.irq_set_affinity	= irq_chip_set_affinity_parent,
 	.irq_ack		= irq_chip_ack_parent,
 	.irq_mask		= hv_irq_mask,
 	.irq_unmask		= hv_irq_unmask,
 };
 
 static struct msi_domain_ops hv_msi_ops = {
-	.msi_prepare	= pci_msi_prepare,
+	.msi_prepare	= hv_msi_prepare,
 	.msi_free	= hv_msi_free,
 };
 
@@ -1625,12 +1648,12 @@ static int hv_pcie_init_irq_domain(struct hv_pcibus_device *hbus)
 	hbus->msi_info.flags = (MSI_FLAG_USE_DEF_DOM_OPS |
 		MSI_FLAG_USE_DEF_CHIP_OPS | MSI_FLAG_MULTI_PCI_MSI |
 		MSI_FLAG_PCI_MSIX);
-	hbus->msi_info.handler = handle_edge_irq;
-	hbus->msi_info.handler_name = "edge";
+	hbus->msi_info.handler = FLOW_HANDLER;
+	hbus->msi_info.handler_name = FLOW_NAME;
 	hbus->msi_info.data = hbus;
 	hbus->irq_domain = pci_msi_create_irq_domain(hbus->fwnode,
 						     &hbus->msi_info,
-						     x86_vector_domain);
+						     hv_pci_get_root_domain());
 	if (!hbus->irq_domain) {
 		dev_err(&hbus->hdev->device,
 			"Failed to build an MSI IRQ domain\n");
@@ -3542,9 +3565,15 @@ static void __exit exit_hv_pci_drv(void)
 
 static int __init init_hv_pci_drv(void)
 {
+	int ret;
+
 	if (!hv_is_hyperv_initialized())
 		return -ENODEV;
 
+	ret = hv_pci_irqchip_init();
+	if (ret)
+		return ret;
+
 	/* Set the invalid domain number's bit, so it will not be used */
 	set_bit(HVPCI_DOM_INVALID, hvpci_dom_map);
 
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index 8ed6733d5146..8f97c2927bee 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -540,39 +540,6 @@ enum hv_interrupt_source {
 	HV_INTERRUPT_SOURCE_IOAPIC,
 };
 
-union hv_msi_address_register {
-	u32 as_uint32;
-	struct {
-		u32 reserved1:2;
-		u32 destination_mode:1;
-		u32 redirection_hint:1;
-		u32 reserved2:8;
-		u32 destination_id:8;
-		u32 msi_base:12;
-	};
-} __packed;
-
-union hv_msi_data_register {
-	u32 as_uint32;
-	struct {
-		u32 vector:8;
-		u32 delivery_mode:3;
-		u32 reserved1:3;
-		u32 level_assert:1;
-		u32 trigger_mode:1;
-		u32 reserved2:16;
-	};
-} __packed;
-
-/* HvRetargetDeviceInterrupt hypercall */
-union hv_msi_entry {
-	u64 as_uint64;
-	struct {
-		union hv_msi_address_register address;
-		union hv_msi_data_register data;
-	} __packed;
-};
-
 union hv_ioapic_rte {
 	u64 as_uint64;
 
-- 
2.25.1

[PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

[Sunil Muthuswamy]

From: Sunil Muthuswamy <sunilmut@microsoft.com>

Add arm64 Hyper-V vPCI support by implementing the arch specific
interfaces. Introduce an IRQ domain and chip specific to Hyper-v vPCI that
is based on SPIs. The IRQ domain parents itself to the arch GIC IRQ domain
for basic vector management.

Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
---
In v2, v3, v4, v5, v6 & v7:
 Changes are described in the cover letter.

 arch/arm64/include/asm/hyperv-tlfs.h |   9 +
 drivers/pci/Kconfig                  |   2 +-
 drivers/pci/controller/Kconfig       |   2 +-
 drivers/pci/controller/pci-hyperv.c  | 241 ++++++++++++++++++++++++++-
 4 files changed, 251 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/hyperv-tlfs.h b/arch/arm64/include/asm/hyperv-tlfs.h
index 4d964a7f02ee..bc6c7ac934a1 100644
--- a/arch/arm64/include/asm/hyperv-tlfs.h
+++ b/arch/arm64/include/asm/hyperv-tlfs.h
@@ -64,6 +64,15 @@
 #define HV_REGISTER_STIMER0_CONFIG	0x000B0000
 #define HV_REGISTER_STIMER0_COUNT	0x000B0001
 
+union hv_msi_entry {
+	u64 as_uint64[2];
+	struct {
+		u64 address;
+		u32 data;
+		u32 reserved;
+	} __packed;
+};
+
 #include <asm-generic/hyperv-tlfs.h>
 
 #endif
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 43e615aa12ff..d98fafdd0f99 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -184,7 +184,7 @@ config PCI_LABEL
 
 config PCI_HYPERV
 	tristate "Hyper-V PCI Frontend"
-	depends on X86_64 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
+	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
 	select PCI_HYPERV_INTERFACE
 	help
 	  The PCI device frontend driver allows the kernel to import arbitrary
diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
index 93b141110537..2536abcc045a 100644
--- a/drivers/pci/controller/Kconfig
+++ b/drivers/pci/controller/Kconfig
@@ -281,7 +281,7 @@ config PCIE_BRCMSTB
 
 config PCI_HYPERV_INTERFACE
 	tristate "Hyper-V PCI Interface"
-	depends on X86 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && X86_64
+	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN
 	help
 	  The Hyper-V PCI Interface is a helper driver allows other drivers to
 	  have a common interface with the Hyper-V PCI frontend driver.
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index ead7d6cb6bf1..02ba2e7e2618 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -47,6 +47,8 @@
 #include <linux/msi.h>
 #include <linux/hyperv.h>
 #include <linux/refcount.h>
+#include <linux/irqdomain.h>
+#include <linux/acpi.h>
 #include <asm/mshyperv.h>
 
 /*
@@ -614,7 +616,236 @@ static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
 {
 	return pci_msi_prepare(domain, dev, nvec, info);
 }
-#endif /* CONFIG_X86 */
+#elif defined(CONFIG_ARM64)
+/*
+ * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
+ * of room at the start to allow for SPIs to be specified through ACPI and
+ * starting with a power of two to satisfy power of 2 multi-MSI requirement.
+ */
+#define HV_PCI_MSI_SPI_START	64
+#define HV_PCI_MSI_SPI_NR	(1020 - HV_PCI_MSI_SPI_START)
+#define DELIVERY_MODE		0
+#define FLOW_HANDLER		NULL
+#define FLOW_NAME		NULL
+#define hv_msi_prepare		NULL
+
+struct hv_pci_chip_data {
+	DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
+	struct mutex	map_lock;
+};
+
+/* Hyper-V vPCI MSI GIC IRQ domain */
+static struct irq_domain *hv_msi_gic_irq_domain;
+
+/* Hyper-V PCI MSI IRQ chip */
+static struct irq_chip hv_arm64_msi_irq_chip = {
+	.name = "MSI",
+	.irq_set_affinity = irq_chip_set_affinity_parent,
+	.irq_eoi = irq_chip_eoi_parent,
+	.irq_mask = irq_chip_mask_parent,
+	.irq_unmask = irq_chip_unmask_parent
+};
+
+static unsigned int hv_msi_get_int_vector(struct irq_data *irqd)
+{
+	return irqd->parent_data->hwirq;
+}
+
+static void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
+				       struct msi_desc *msi_desc)
+{
+	msi_entry->address = ((u64)msi_desc->msg.address_hi << 32) |
+			      msi_desc->msg.address_lo;
+	msi_entry->data = msi_desc->msg.data;
+}
+
+/*
+ * @nr_bm_irqs:		Indicates the number of IRQs that were allocated from
+ *			the bitmap.
+ * @nr_dom_irqs:	Indicates the number of IRQs that were allocated from
+ *			the parent domain.
+ */
+static void hv_pci_vec_irq_free(struct irq_domain *domain,
+				unsigned int virq,
+				unsigned int nr_bm_irqs,
+				unsigned int nr_dom_irqs)
+{
+	struct hv_pci_chip_data *chip_data = domain->host_data;
+	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
+	int first = d->hwirq - HV_PCI_MSI_SPI_START;
+	int i;
+
+	mutex_lock(&chip_data->map_lock);
+	bitmap_release_region(chip_data->spi_map,
+			      first,
+			      get_count_order(nr_bm_irqs));
+	mutex_unlock(&chip_data->map_lock);
+	for (i = 0; i < nr_dom_irqs; i++) {
+		if (i)
+			d = irq_domain_get_irq_data(domain, virq + i);
+		irq_domain_reset_irq_data(d);
+	}
+
+	irq_domain_free_irqs_parent(domain, virq, nr_dom_irqs);
+}
+
+static void hv_pci_vec_irq_domain_free(struct irq_domain *domain,
+				       unsigned int virq,
+				       unsigned int nr_irqs)
+{
+	hv_pci_vec_irq_free(domain, virq, nr_irqs, nr_irqs);
+}
+
+static int hv_pci_vec_alloc_device_irq(struct irq_domain *domain,
+				       unsigned int nr_irqs,
+				       irq_hw_number_t *hwirq)
+{
+	struct hv_pci_chip_data *chip_data = domain->host_data;
+	unsigned int index;
+
+	/* Find and allocate region from the SPI bitmap */
+	mutex_lock(&chip_data->map_lock);
+	index = bitmap_find_free_region(chip_data->spi_map,
+					HV_PCI_MSI_SPI_NR,
+					get_count_order(nr_irqs));
+	mutex_unlock(&chip_data->map_lock);
+	if (index < 0)
+		return -ENOSPC;
+
+	*hwirq = index + HV_PCI_MSI_SPI_START;
+
+	return 0;
+}
+
+static int hv_pci_vec_irq_gic_domain_alloc(struct irq_domain *domain,
+					   unsigned int virq,
+					   irq_hw_number_t hwirq)
+{
+	struct irq_fwspec fwspec;
+	struct irq_data *d;
+	int ret;
+
+	fwspec.fwnode = domain->parent->fwnode;
+	fwspec.param_count = 2;
+	fwspec.param[0] = hwirq;
+	fwspec.param[1] = IRQ_TYPE_EDGE_RISING;
+
+	ret = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
+	if (ret)
+		return ret;
+
+	/*
+	 * Since the interrupt specifier is not coming from ACPI or DT, the
+	 * trigger type will need to be set explicitly. Otherwise, it will be
+	 * set to whatever is in the GIC configuration.
+	 */
+	d = irq_domain_get_irq_data(domain->parent, virq);
+
+	return d->chip->irq_set_type(d, IRQ_TYPE_EDGE_RISING);
+}
+
+static int hv_pci_vec_irq_domain_alloc(struct irq_domain *domain,
+				       unsigned int virq, unsigned int nr_irqs,
+				       void *args)
+{
+	irq_hw_number_t hwirq;
+	unsigned int i;
+	int ret;
+
+	ret = hv_pci_vec_alloc_device_irq(domain, nr_irqs, &hwirq);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < nr_irqs; i++) {
+		ret = hv_pci_vec_irq_gic_domain_alloc(domain, virq + i,
+						      hwirq + i);
+		if (ret)
+			goto free_irq;
+
+		ret = irq_domain_set_hwirq_and_chip(domain, virq + i,
+						    hwirq + i,
+						    &hv_arm64_msi_irq_chip,
+						    domain->host_data);
+		if (ret)
+			goto free_irq;
+
+		pr_debug("pID:%d vID:%u\n", (int)(hwirq + i), virq + i);
+	}
+
+	return 0;
+
+free_irq:
+	hv_pci_vec_irq_free(domain, virq, nr_irqs, i);
+
+	return ret;
+}
+
+/*
+ * Pick the first online cpu as the irq affinity that can be temporarily used
+ * for composing MSI from the hypervisor. GIC will eventually set the right
+ * affinity for the irq and the 'unmask' will retarget the interrupt to that
+ * cpu.
+ */
+static int hv_pci_vec_irq_domain_activate(struct irq_domain *domain,
+					  struct irq_data *irqd, bool reserve)
+{
+	int cpu = cpumask_first(cpu_online_mask);
+
+	irq_data_update_effective_affinity(irqd, cpumask_of(cpu));
+
+	return 0;
+}
+
+static const struct irq_domain_ops hv_pci_domain_ops = {
+	.alloc	= hv_pci_vec_irq_domain_alloc,
+	.free	= hv_pci_vec_irq_domain_free,
+	.activate = hv_pci_vec_irq_domain_activate,
+};
+
+static int hv_pci_irqchip_init(void)
+{
+	static struct hv_pci_chip_data *chip_data;
+	struct fwnode_handle *fn = NULL;
+	int ret = -ENOMEM;
+
+	chip_data = kzalloc(sizeof(*chip_data), GFP_KERNEL);
+	if (!chip_data)
+		return ret;
+
+	mutex_init(&chip_data->map_lock);
+	fn = irq_domain_alloc_named_fwnode("hv_vpci_arm64");
+	if (!fn)
+		goto free_chip;
+
+	/*
+	 * IRQ domain once enabled, should not be removed since there is no
+	 * way to ensure that all the corresponding devices are also gone and
+	 * no interrupts will be generated.
+	 */
+	hv_msi_gic_irq_domain = acpi_irq_create_hierarchy(0, HV_PCI_MSI_SPI_NR,
+							  fn, &hv_pci_domain_ops,
+							  chip_data);
+
+	if (!hv_msi_gic_irq_domain) {
+		pr_err("Failed to create Hyper-V arm64 vPCI MSI IRQ domain\n");
+		goto free_chip;
+	}
+
+	return 0;
+
+free_chip:
+	kfree(chip_data);
+	if (fn)
+		irq_domain_free_fwnode(fn);
+
+	return ret;
+}
+
+static struct irq_domain *hv_pci_get_root_domain(void)
+{
+	return hv_msi_gic_irq_domain;
+}
+#endif /* CONFIG_ARM64 */
 
 /**
  * hv_pci_generic_compl() - Invoked for a completion packet
@@ -1227,6 +1458,8 @@ static void hv_msi_free(struct irq_domain *domain, struct msi_domain_info *info,
 static void hv_irq_mask(struct irq_data *data)
 {
 	pci_msi_mask_irq(data);
+	if (data->parent_data->chip->irq_mask)
+		irq_chip_mask_parent(data);
 }
 
 /**
@@ -1343,6 +1576,8 @@ static void hv_irq_unmask(struct irq_data *data)
 		dev_err(&hbus->hdev->device,
 			"%s() failed: %#llx", __func__, res);
 
+	if (data->parent_data->chip->irq_unmask)
+		irq_chip_unmask_parent(data);
 	pci_msi_unmask_irq(data);
 }
 
@@ -1618,7 +1853,11 @@ static struct irq_chip hv_msi_irq_chip = {
 	.name			= "Hyper-V PCIe MSI",
 	.irq_compose_msi_msg	= hv_compose_msi_msg,
 	.irq_set_affinity	= irq_chip_set_affinity_parent,
+#ifdef CONFIG_X86
 	.irq_ack		= irq_chip_ack_parent,
+#elif defined(CONFIG_ARM64)
+	.irq_eoi		= irq_chip_eoi_parent,
+#endif
 	.irq_mask		= hv_irq_mask,
 	.irq_unmask		= hv_irq_unmask,
 };
-- 
2.25.1

RE: [PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

[Michael Kelley (LINUX)]

From: Sunil Muthuswamy <sunilmut@linux.microsoft.com> Sent: Friday, December 17, 2021 10:52 AM
> 
> Add arm64 Hyper-V vPCI support by implementing the arch specific
> interfaces. Introduce an IRQ domain and chip specific to Hyper-v vPCI that
> is based on SPIs. The IRQ domain parents itself to the arch GIC IRQ domain
> for basic vector management.
> 
> Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> ---
> In v2, v3, v4, v5, v6 & v7:
>  Changes are described in the cover letter.
> 
>  arch/arm64/include/asm/hyperv-tlfs.h |   9 +
>  drivers/pci/Kconfig                  |   2 +-
>  drivers/pci/controller/Kconfig       |   2 +-
>  drivers/pci/controller/pci-hyperv.c  | 241 ++++++++++++++++++++++++++-
>  4 files changed, 251 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/hyperv-tlfs.h b/arch/arm64/include/asm/hyperv-tlfs.h
> index 4d964a7f02ee..bc6c7ac934a1 100644
> --- a/arch/arm64/include/asm/hyperv-tlfs.h
> +++ b/arch/arm64/include/asm/hyperv-tlfs.h
> @@ -64,6 +64,15 @@
>  #define HV_REGISTER_STIMER0_CONFIG	0x000B0000
>  #define HV_REGISTER_STIMER0_COUNT	0x000B0001
> 
> +union hv_msi_entry {
> +	u64 as_uint64[2];
> +	struct {
> +		u64 address;
> +		u32 data;
> +		u32 reserved;
> +	} __packed;
> +};
> +
>  #include <asm-generic/hyperv-tlfs.h>
> 
>  #endif
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 43e615aa12ff..d98fafdd0f99 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -184,7 +184,7 @@ config PCI_LABEL
> 
>  config PCI_HYPERV
>  	tristate "Hyper-V PCI Frontend"
> -	depends on X86_64 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
> +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
>  	select PCI_HYPERV_INTERFACE
>  	help
>  	  The PCI device frontend driver allows the kernel to import arbitrary
> diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
> index 93b141110537..2536abcc045a 100644
> --- a/drivers/pci/controller/Kconfig
> +++ b/drivers/pci/controller/Kconfig
> @@ -281,7 +281,7 @@ config PCIE_BRCMSTB
> 
>  config PCI_HYPERV_INTERFACE
>  	tristate "Hyper-V PCI Interface"
> -	depends on X86 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && X86_64
> +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN
>  	help
>  	  The Hyper-V PCI Interface is a helper driver allows other drivers to
>  	  have a common interface with the Hyper-V PCI frontend driver.
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index ead7d6cb6bf1..02ba2e7e2618 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -47,6 +47,8 @@
>  #include <linux/msi.h>
>  #include <linux/hyperv.h>
>  #include <linux/refcount.h>
> +#include <linux/irqdomain.h>
> +#include <linux/acpi.h>
>  #include <asm/mshyperv.h>
> 
>  /*
> @@ -614,7 +616,236 @@ static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
>  {
>  	return pci_msi_prepare(domain, dev, nvec, info);
>  }
> -#endif /* CONFIG_X86 */
> +#elif defined(CONFIG_ARM64)
> +/*
> + * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
> + * of room at the start to allow for SPIs to be specified through ACPI and
> + * starting with a power of two to satisfy power of 2 multi-MSI requirement.
> + */
> +#define HV_PCI_MSI_SPI_START	64
> +#define HV_PCI_MSI_SPI_NR	(1020 - HV_PCI_MSI_SPI_START)
> +#define DELIVERY_MODE		0
> +#define FLOW_HANDLER		NULL
> +#define FLOW_NAME		NULL
> +#define hv_msi_prepare		NULL
> +
> +struct hv_pci_chip_data {
> +	DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
> +	struct mutex	map_lock;
> +};
> +
> +/* Hyper-V vPCI MSI GIC IRQ domain */
> +static struct irq_domain *hv_msi_gic_irq_domain;
> +
> +/* Hyper-V PCI MSI IRQ chip */
> +static struct irq_chip hv_arm64_msi_irq_chip = {
> +	.name = "MSI",
> +	.irq_set_affinity = irq_chip_set_affinity_parent,
> +	.irq_eoi = irq_chip_eoi_parent,
> +	.irq_mask = irq_chip_mask_parent,
> +	.irq_unmask = irq_chip_unmask_parent
> +};
> +
> +static unsigned int hv_msi_get_int_vector(struct irq_data *irqd)
> +{
> +	return irqd->parent_data->hwirq;
> +}
> +
> +static void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
> +				       struct msi_desc *msi_desc)
> +{
> +	msi_entry->address = ((u64)msi_desc->msg.address_hi << 32) |
> +			      msi_desc->msg.address_lo;
> +	msi_entry->data = msi_desc->msg.data;
> +}
> +
> +/*
> + * @nr_bm_irqs:		Indicates the number of IRQs that were allocated from
> + *			the bitmap.
> + * @nr_dom_irqs:	Indicates the number of IRQs that were allocated from
> + *			the parent domain.
> + */
> +static void hv_pci_vec_irq_free(struct irq_domain *domain,
> +				unsigned int virq,
> +				unsigned int nr_bm_irqs,
> +				unsigned int nr_dom_irqs)
> +{
> +	struct hv_pci_chip_data *chip_data = domain->host_data;
> +	struct irq_data *d = irq_domain_get_irq_data(domain, virq);

FWIW, irq_domain_get_irq_data() can return NULL.   Maybe that's an
error in the "should never happen" category.   Throughout kernel code,
some callers check for a NULL result, but a lot do not.

> +	int first = d->hwirq - HV_PCI_MSI_SPI_START;
> +	int i;
> +
> +	mutex_lock(&chip_data->map_lock);
> +	bitmap_release_region(chip_data->spi_map,
> +			      first,
> +			      get_count_order(nr_bm_irqs));
> +	mutex_unlock(&chip_data->map_lock);
> +	for (i = 0; i < nr_dom_irqs; i++) {
> +		if (i)
> +			d = irq_domain_get_irq_data(domain, virq + i);

Same here.

> +		irq_domain_reset_irq_data(d);
> +	}
> +
> +	irq_domain_free_irqs_parent(domain, virq, nr_dom_irqs);
> +}
> +
> +static void hv_pci_vec_irq_domain_free(struct irq_domain *domain,
> +				       unsigned int virq,
> +				       unsigned int nr_irqs)
> +{
> +	hv_pci_vec_irq_free(domain, virq, nr_irqs, nr_irqs);
> +}
> +
> +static int hv_pci_vec_alloc_device_irq(struct irq_domain *domain,
> +				       unsigned int nr_irqs,
> +				       irq_hw_number_t *hwirq)
> +{
> +	struct hv_pci_chip_data *chip_data = domain->host_data;
> +	unsigned int index;
> +
> +	/* Find and allocate region from the SPI bitmap */
> +	mutex_lock(&chip_data->map_lock);
> +	index = bitmap_find_free_region(chip_data->spi_map,
> +					HV_PCI_MSI_SPI_NR,
> +					get_count_order(nr_irqs));
> +	mutex_unlock(&chip_data->map_lock);
> +	if (index < 0)
> +		return -ENOSPC;
> +
> +	*hwirq = index + HV_PCI_MSI_SPI_START;
> +
> +	return 0;
> +}
> +
> +static int hv_pci_vec_irq_gic_domain_alloc(struct irq_domain *domain,
> +					   unsigned int virq,
> +					   irq_hw_number_t hwirq)
> +{
> +	struct irq_fwspec fwspec;
> +	struct irq_data *d;
> +	int ret;
> +
> +	fwspec.fwnode = domain->parent->fwnode;
> +	fwspec.param_count = 2;
> +	fwspec.param[0] = hwirq;
> +	fwspec.param[1] = IRQ_TYPE_EDGE_RISING;
> +
> +	ret = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Since the interrupt specifier is not coming from ACPI or DT, the
> +	 * trigger type will need to be set explicitly. Otherwise, it will be
> +	 * set to whatever is in the GIC configuration.
> +	 */
> +	d = irq_domain_get_irq_data(domain->parent, virq);

And here.

> +
> +	return d->chip->irq_set_type(d, IRQ_TYPE_EDGE_RISING);
> +}
> +
> +static int hv_pci_vec_irq_domain_alloc(struct irq_domain *domain,
> +				       unsigned int virq, unsigned int nr_irqs,
> +				       void *args)
> +{
> +	irq_hw_number_t hwirq;
> +	unsigned int i;
> +	int ret;
> +
> +	ret = hv_pci_vec_alloc_device_irq(domain, nr_irqs, &hwirq);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		ret = hv_pci_vec_irq_gic_domain_alloc(domain, virq + i,
> +						      hwirq + i);
> +		if (ret)
> +			goto free_irq;
> +
> +		ret = irq_domain_set_hwirq_and_chip(domain, virq + i,
> +						    hwirq + i,
> +						    &hv_arm64_msi_irq_chip,
> +						    domain->host_data);
> +		if (ret)
> +			goto free_irq;

This error path doesn't clean up correctly.  While parent IRQs allocated
in previous iterations of the loop is cleaned up, the parent IRQ
allocated in the current iteration is not.

> +
> +		pr_debug("pID:%d vID:%u\n", (int)(hwirq + i), virq + i);
> +	}
> +
> +	return 0;
> +
> +free_irq:
> +	hv_pci_vec_irq_free(domain, virq, nr_irqs, i);
> +
> +	return ret;
> +}
> +
> +/*
> + * Pick the first online cpu as the irq affinity that can be temporarily used
> + * for composing MSI from the hypervisor. GIC will eventually set the right
> + * affinity for the irq and the 'unmask' will retarget the interrupt to that
> + * cpu.
> + */
> +static int hv_pci_vec_irq_domain_activate(struct irq_domain *domain,
> +					  struct irq_data *irqd, bool reserve)
> +{
> +	int cpu = cpumask_first(cpu_online_mask);

Using the cpu_online_mask may work correctly, though its usage here
raises a red flag for me.  The problem is that the CPU selected can go offline
immediately after the above line of code, as the cpus_read_lock() does
not appear to be held anywhere in the call stack.  If the CPU is only
a temporary placeholder and will never actually be targeted with the
interrupt, then maybe the online/offline state doesn't matter.   But if
that's the case, I'd suggest using the cpu_present_mask instead of the
cpu_online_mask.  Hyper-V doesn't hot-add CPUs, so cpu_present_mask
should be stable even if the cpus_read_lock() isn't held, and the code
doesn't incorrectly imply that it's important for the CPU to be online.

Michael

> +
> +	irq_data_update_effective_affinity(irqd, cpumask_of(cpu));
> +
> +	return 0;
> +}
> +
> +static const struct irq_domain_ops hv_pci_domain_ops = {
> +	.alloc	= hv_pci_vec_irq_domain_alloc,
> +	.free	= hv_pci_vec_irq_domain_free,
> +	.activate = hv_pci_vec_irq_domain_activate,
> +};
> +
> +static int hv_pci_irqchip_init(void)
> +{
> +	static struct hv_pci_chip_data *chip_data;
> +	struct fwnode_handle *fn = NULL;
> +	int ret = -ENOMEM;
> +
> +	chip_data = kzalloc(sizeof(*chip_data), GFP_KERNEL);
> +	if (!chip_data)
> +		return ret;
> +
> +	mutex_init(&chip_data->map_lock);
> +	fn = irq_domain_alloc_named_fwnode("hv_vpci_arm64");
> +	if (!fn)
> +		goto free_chip;
> +
> +	/*
> +	 * IRQ domain once enabled, should not be removed since there is no
> +	 * way to ensure that all the corresponding devices are also gone and
> +	 * no interrupts will be generated.
> +	 */
> +	hv_msi_gic_irq_domain = acpi_irq_create_hierarchy(0, HV_PCI_MSI_SPI_NR,
> +							  fn, &hv_pci_domain_ops,
> +							  chip_data);
> +
> +	if (!hv_msi_gic_irq_domain) {
> +		pr_err("Failed to create Hyper-V arm64 vPCI MSI IRQ domain\n");
> +		goto free_chip;
> +	}
> +
> +	return 0;
> +
> +free_chip:
> +	kfree(chip_data);
> +	if (fn)
> +		irq_domain_free_fwnode(fn);
> +
> +	return ret;
> +}
> +
> +static struct irq_domain *hv_pci_get_root_domain(void)
> +{
> +	return hv_msi_gic_irq_domain;
> +}
> +#endif /* CONFIG_ARM64 */
> 
>  /**
>   * hv_pci_generic_compl() - Invoked for a completion packet
> @@ -1227,6 +1458,8 @@ static void hv_msi_free(struct irq_domain *domain, struct msi_domain_info *info,
>  static void hv_irq_mask(struct irq_data *data)
>  {
>  	pci_msi_mask_irq(data);
> +	if (data->parent_data->chip->irq_mask)
> +		irq_chip_mask_parent(data);
>  }
> 
>  /**
> @@ -1343,6 +1576,8 @@ static void hv_irq_unmask(struct irq_data *data)
>  		dev_err(&hbus->hdev->device,
>  			"%s() failed: %#llx", __func__, res);
> 
> +	if (data->parent_data->chip->irq_unmask)
> +		irq_chip_unmask_parent(data);
>  	pci_msi_unmask_irq(data);
>  }
> 
> @@ -1618,7 +1853,11 @@ static struct irq_chip hv_msi_irq_chip = {
>  	.name			= "Hyper-V PCIe MSI",
>  	.irq_compose_msi_msg	= hv_compose_msi_msg,
>  	.irq_set_affinity	= irq_chip_set_affinity_parent,
> +#ifdef CONFIG_X86
>  	.irq_ack		= irq_chip_ack_parent,
> +#elif defined(CONFIG_ARM64)
> +	.irq_eoi		= irq_chip_eoi_parent,
> +#endif
>  	.irq_mask		= hv_irq_mask,
>  	.irq_unmask		= hv_irq_unmask,
>  };
> --
> 2.25.1
> 

Re: [PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

[Marc Zyngier]

On Mon, 27 Dec 2021 17:38:07 +0000,
"Michael Kelley (LINUX)" <mikelley@microsoft.com> wrote:
> 
> From: Sunil Muthuswamy <sunilmut@linux.microsoft.com> Sent: Friday, December 17, 2021 10:52 AM
> > 
> > Add arm64 Hyper-V vPCI support by implementing the arch specific
> > interfaces. Introduce an IRQ domain and chip specific to Hyper-v vPCI that
> > is based on SPIs. The IRQ domain parents itself to the arch GIC IRQ domain
> > for basic vector management.
> > 
> > Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> > ---
> > In v2, v3, v4, v5, v6 & v7:
> >  Changes are described in the cover letter.
> > 
> >  arch/arm64/include/asm/hyperv-tlfs.h |   9 +
> >  drivers/pci/Kconfig                  |   2 +-
> >  drivers/pci/controller/Kconfig       |   2 +-
> >  drivers/pci/controller/pci-hyperv.c  | 241 ++++++++++++++++++++++++++-
> >  4 files changed, 251 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/hyperv-tlfs.h b/arch/arm64/include/asm/hyperv-tlfs.h
> > index 4d964a7f02ee..bc6c7ac934a1 100644
> > --- a/arch/arm64/include/asm/hyperv-tlfs.h
> > +++ b/arch/arm64/include/asm/hyperv-tlfs.h
> > @@ -64,6 +64,15 @@
> >  #define HV_REGISTER_STIMER0_CONFIG	0x000B0000
> >  #define HV_REGISTER_STIMER0_COUNT	0x000B0001
> > 
> > +union hv_msi_entry {
> > +	u64 as_uint64[2];
> > +	struct {
> > +		u64 address;
> > +		u32 data;
> > +		u32 reserved;
> > +	} __packed;
> > +};
> > +
> >  #include <asm-generic/hyperv-tlfs.h>
> > 
> >  #endif
> > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> > index 43e615aa12ff..d98fafdd0f99 100644
> > --- a/drivers/pci/Kconfig
> > +++ b/drivers/pci/Kconfig
> > @@ -184,7 +184,7 @@ config PCI_LABEL
> > 
> >  config PCI_HYPERV
> >  	tristate "Hyper-V PCI Frontend"
> > -	depends on X86_64 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
> > +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && SYSFS
> >  	select PCI_HYPERV_INTERFACE
> >  	help
> >  	  The PCI device frontend driver allows the kernel to import arbitrary
> > diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
> > index 93b141110537..2536abcc045a 100644
> > --- a/drivers/pci/controller/Kconfig
> > +++ b/drivers/pci/controller/Kconfig
> > @@ -281,7 +281,7 @@ config PCIE_BRCMSTB
> > 
> >  config PCI_HYPERV_INTERFACE
> >  	tristate "Hyper-V PCI Interface"
> > -	depends on X86 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && X86_64
> > +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN
> >  	help
> >  	  The Hyper-V PCI Interface is a helper driver allows other drivers to
> >  	  have a common interface with the Hyper-V PCI frontend driver.
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> > index ead7d6cb6bf1..02ba2e7e2618 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -47,6 +47,8 @@
> >  #include <linux/msi.h>
> >  #include <linux/hyperv.h>
> >  #include <linux/refcount.h>
> > +#include <linux/irqdomain.h>
> > +#include <linux/acpi.h>
> >  #include <asm/mshyperv.h>
> > 
> >  /*
> > @@ -614,7 +616,236 @@ static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
> >  {
> >  	return pci_msi_prepare(domain, dev, nvec, info);
> >  }
> > -#endif /* CONFIG_X86 */
> > +#elif defined(CONFIG_ARM64)
> > +/*
> > + * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
> > + * of room at the start to allow for SPIs to be specified through ACPI and
> > + * starting with a power of two to satisfy power of 2 multi-MSI requirement.
> > + */
> > +#define HV_PCI_MSI_SPI_START	64
> > +#define HV_PCI_MSI_SPI_NR	(1020 - HV_PCI_MSI_SPI_START)
> > +#define DELIVERY_MODE		0
> > +#define FLOW_HANDLER		NULL
> > +#define FLOW_NAME		NULL
> > +#define hv_msi_prepare		NULL
> > +
> > +struct hv_pci_chip_data {
> > +	DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
> > +	struct mutex	map_lock;
> > +};
> > +
> > +/* Hyper-V vPCI MSI GIC IRQ domain */
> > +static struct irq_domain *hv_msi_gic_irq_domain;
> > +
> > +/* Hyper-V PCI MSI IRQ chip */
> > +static struct irq_chip hv_arm64_msi_irq_chip = {
> > +	.name = "MSI",
> > +	.irq_set_affinity = irq_chip_set_affinity_parent,
> > +	.irq_eoi = irq_chip_eoi_parent,
> > +	.irq_mask = irq_chip_mask_parent,
> > +	.irq_unmask = irq_chip_unmask_parent
> > +};
> > +
> > +static unsigned int hv_msi_get_int_vector(struct irq_data *irqd)
> > +{
> > +	return irqd->parent_data->hwirq;
> > +}
> > +
> > +static void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
> > +				       struct msi_desc *msi_desc)
> > +{
> > +	msi_entry->address = ((u64)msi_desc->msg.address_hi << 32) |
> > +			      msi_desc->msg.address_lo;
> > +	msi_entry->data = msi_desc->msg.data;
> > +}
> > +
> > +/*
> > + * @nr_bm_irqs:		Indicates the number of IRQs that were allocated from
> > + *			the bitmap.
> > + * @nr_dom_irqs:	Indicates the number of IRQs that were allocated from
> > + *			the parent domain.
> > + */
> > +static void hv_pci_vec_irq_free(struct irq_domain *domain,
> > +				unsigned int virq,
> > +				unsigned int nr_bm_irqs,
> > +				unsigned int nr_dom_irqs)
> > +{
> > +	struct hv_pci_chip_data *chip_data = domain->host_data;
> > +	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
> 
> FWIW, irq_domain_get_irq_data() can return NULL.   Maybe that's an
> error in the "should never happen" category.   Throughout kernel code,
> some callers check for a NULL result, but a lot do not.

irq_domain_get_irq_data() returns NULL when there is no mapping. If
this happens here, then the allocation tracking has gone horribly
wrong, and I certainly want to see the resulting Oops rather than
papering over it.

	M.

-- 
Without deviation from the norm, progress is not possible.

RE: [PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

[Sunil Muthuswamy]

On Mon, 27 Dec 2021 17:38:07 +0000,
"Michael Kelley (LINUX)" <mikelley@microsoft.com> wrote:
> 
> From: Sunil Muthuswamy <sunilmut@linux.microsoft.com> Sent: Friday,
> December 17, 2021 10:52 AM
> >
> > Add arm64 Hyper-V vPCI support by implementing the arch specific
> > interfaces. Introduce an IRQ domain and chip specific to Hyper-v vPCI that
> > is based on SPIs. The IRQ domain parents itself to the arch GIC IRQ domain
> > for basic vector management.
> >
> > Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> > ---
> > In v2, v3, v4, v5, v6 & v7:
> >  Changes are described in the cover letter.
> >
> >  arch/arm64/include/asm/hyperv-tlfs.h |   9 +
> >  drivers/pci/Kconfig                  |   2 +-
> >  drivers/pci/controller/Kconfig       |   2 +-
> >  drivers/pci/controller/pci-hyperv.c  | 241
> ++++++++++++++++++++++++++-
> >  4 files changed, 251 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/hyperv-tlfs.h
> b/arch/arm64/include/asm/hyperv-tlfs.h
> > index 4d964a7f02ee..bc6c7ac934a1 100644
> > --- a/arch/arm64/include/asm/hyperv-tlfs.h
> > +++ b/arch/arm64/include/asm/hyperv-tlfs.h
> > @@ -64,6 +64,15 @@
> >  #define HV_REGISTER_STIMER0_CONFIG	0x000B0000
> >  #define HV_REGISTER_STIMER0_COUNT	0x000B0001
> >
> > +union hv_msi_entry {
> > +	u64 as_uint64[2];
> > +	struct {
> > +		u64 address;
> > +		u32 data;
> > +		u32 reserved;
> > +	} __packed;
> > +};
> > +
> >  #include <asm-generic/hyperv-tlfs.h>
> >
> >  #endif
> > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> > index 43e615aa12ff..d98fafdd0f99 100644
> > --- a/drivers/pci/Kconfig
> > +++ b/drivers/pci/Kconfig
> > @@ -184,7 +184,7 @@ config PCI_LABEL
> >
> >  config PCI_HYPERV
> >  	tristate "Hyper-V PCI Frontend"
> > -	depends on X86_64 && HYPERV && PCI_MSI &&
> PCI_MSI_IRQ_DOMAIN && SYSFS
> > +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI
> && PCI_MSI_IRQ_DOMAIN && SYSFS
> >  	select PCI_HYPERV_INTERFACE
> >  	help
> >  	  The PCI device frontend driver allows the kernel to import arbitrary
> > diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
> > index 93b141110537..2536abcc045a 100644
> > --- a/drivers/pci/controller/Kconfig
> > +++ b/drivers/pci/controller/Kconfig
> > @@ -281,7 +281,7 @@ config PCIE_BRCMSTB
> >
> >  config PCI_HYPERV_INTERFACE
> >  	tristate "Hyper-V PCI Interface"
> > -	depends on X86 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN
> && X86_64
> > +	depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI
> && PCI_MSI_IRQ_DOMAIN
> >  	help
> >  	  The Hyper-V PCI Interface is a helper driver allows other drivers to
> >  	  have a common interface with the Hyper-V PCI frontend driver.
> > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-
> hyperv.c
> > index ead7d6cb6bf1..02ba2e7e2618 100644
> > --- a/drivers/pci/controller/pci-hyperv.c
> > +++ b/drivers/pci/controller/pci-hyperv.c
> > @@ -47,6 +47,8 @@
> >  #include <linux/msi.h>
> >  #include <linux/hyperv.h>
> >  #include <linux/refcount.h>
> > +#include <linux/irqdomain.h>
> > +#include <linux/acpi.h>
> >  #include <asm/mshyperv.h>
> >
> >  /*
> > @@ -614,7 +616,236 @@ static int hv_msi_prepare(struct irq_domain
> *domain, struct device *dev,
> >  {
> >  	return pci_msi_prepare(domain, dev, nvec, info);
> >  }
> > -#endif /* CONFIG_X86 */
> > +#elif defined(CONFIG_ARM64)
> > +/*
> > + * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
> > + * of room at the start to allow for SPIs to be specified through ACPI and
> > + * starting with a power of two to satisfy power of 2 multi-MSI
> requirement.
> > + */
> > +#define HV_PCI_MSI_SPI_START	64
> > +#define HV_PCI_MSI_SPI_NR	(1020 - HV_PCI_MSI_SPI_START)
> > +#define DELIVERY_MODE		0
> > +#define FLOW_HANDLER		NULL
> > +#define FLOW_NAME		NULL
> > +#define hv_msi_prepare		NULL
> > +
> > +struct hv_pci_chip_data {
> > +	DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
> > +	struct mutex	map_lock;
> > +};
> > +
> > +/* Hyper-V vPCI MSI GIC IRQ domain */
> > +static struct irq_domain *hv_msi_gic_irq_domain;
> > +
> > +/* Hyper-V PCI MSI IRQ chip */
> > +static struct irq_chip hv_arm64_msi_irq_chip = {
> > +	.name = "MSI",
> > +	.irq_set_affinity = irq_chip_set_affinity_parent,
> > +	.irq_eoi = irq_chip_eoi_parent,
> > +	.irq_mask = irq_chip_mask_parent,
> > +	.irq_unmask = irq_chip_unmask_parent
> > +};
> > +
> > +static unsigned int hv_msi_get_int_vector(struct irq_data *irqd)
> > +{
> > +	return irqd->parent_data->hwirq;
> > +}
> > +
> > +static void hv_set_msi_entry_from_desc(union hv_msi_entry
> *msi_entry,
> > +				       struct msi_desc *msi_desc)
> > +{
> > +	msi_entry->address = ((u64)msi_desc->msg.address_hi << 32) |
> > +			      msi_desc->msg.address_lo;
> > +	msi_entry->data = msi_desc->msg.data;
> > +}
> > +
> > +/*
> > + * @nr_bm_irqs:		Indicates the number of IRQs that were
> allocated from
> > + *			the bitmap.
> > + * @nr_dom_irqs:	Indicates the number of IRQs that were allocated
> from
> > + *			the parent domain.
> > + */
> > +static void hv_pci_vec_irq_free(struct irq_domain *domain,
> > +				unsigned int virq,
> > +				unsigned int nr_bm_irqs,
> > +				unsigned int nr_dom_irqs)
> > +{
> > +	struct hv_pci_chip_data *chip_data = domain->host_data;
> > +	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
> 
> FWIW, irq_domain_get_irq_data() can return NULL.   Maybe that's an
> error in the "should never happen" category.   Throughout kernel code,
> some callers check for a NULL result, but a lot do not.
> 

Marc's response to this comment makes sense. Will keep this as is, going
by that.

> > +	int first = d->hwirq - HV_PCI_MSI_SPI_START;
> > +	int i;
> > +
> > +	mutex_lock(&chip_data->map_lock);
> > +	bitmap_release_region(chip_data->spi_map,
> > +			      first,
> > +			      get_count_order(nr_bm_irqs));
> > +	mutex_unlock(&chip_data->map_lock);
> > +	for (i = 0; i < nr_dom_irqs; i++) {
> > +		if (i)
> > +			d = irq_domain_get_irq_data(domain, virq + i);
> 
> Same here.
> 

Same response as above.

> > +		irq_domain_reset_irq_data(d);
> > +	}
> > +
> > +	irq_domain_free_irqs_parent(domain, virq, nr_dom_irqs);
> > +}
> > +
> > +static void hv_pci_vec_irq_domain_free(struct irq_domain *domain,
> > +				       unsigned int virq,
> > +				       unsigned int nr_irqs)
> > +{
> > +	hv_pci_vec_irq_free(domain, virq, nr_irqs, nr_irqs);
> > +}
> > +
> > +static int hv_pci_vec_alloc_device_irq(struct irq_domain *domain,
> > +				       unsigned int nr_irqs,
> > +				       irq_hw_number_t *hwirq)
> > +{
> > +	struct hv_pci_chip_data *chip_data = domain->host_data;
> > +	unsigned int index;
> > +
> > +	/* Find and allocate region from the SPI bitmap */
> > +	mutex_lock(&chip_data->map_lock);
> > +	index = bitmap_find_free_region(chip_data->spi_map,
> > +					HV_PCI_MSI_SPI_NR,
> > +					get_count_order(nr_irqs));
> > +	mutex_unlock(&chip_data->map_lock);
> > +	if (index < 0)
> > +		return -ENOSPC;
> > +
> > +	*hwirq = index + HV_PCI_MSI_SPI_START;
> > +
> > +	return 0;
> > +}
> > +
> > +static int hv_pci_vec_irq_gic_domain_alloc(struct irq_domain *domain,
> > +					   unsigned int virq,
> > +					   irq_hw_number_t hwirq)
> > +{
> > +	struct irq_fwspec fwspec;
> > +	struct irq_data *d;
> > +	int ret;
> > +
> > +	fwspec.fwnode = domain->parent->fwnode;
> > +	fwspec.param_count = 2;
> > +	fwspec.param[0] = hwirq;
> > +	fwspec.param[1] = IRQ_TYPE_EDGE_RISING;
> > +
> > +	ret = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/*
> > +	 * Since the interrupt specifier is not coming from ACPI or DT, the
> > +	 * trigger type will need to be set explicitly. Otherwise, it will be
> > +	 * set to whatever is in the GIC configuration.
> > +	 */
> > +	d = irq_domain_get_irq_data(domain->parent, virq);
> 
> And here.
> 

Same response as above.

> > +
> > +	return d->chip->irq_set_type(d, IRQ_TYPE_EDGE_RISING);
> > +}
> > +
> > +static int hv_pci_vec_irq_domain_alloc(struct irq_domain *domain,
> > +				       unsigned int virq, unsigned int nr_irqs,
> > +				       void *args)
> > +{
> > +	irq_hw_number_t hwirq;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	ret = hv_pci_vec_alloc_device_irq(domain, nr_irqs, &hwirq);
> > +	if (ret)
> > +		return ret;
> > +
> > +	for (i = 0; i < nr_irqs; i++) {
> > +		ret = hv_pci_vec_irq_gic_domain_alloc(domain, virq + i,
> > +						      hwirq + i);
> > +		if (ret)
> > +			goto free_irq;
> > +
> > +		ret = irq_domain_set_hwirq_and_chip(domain, virq + i,
> > +						    hwirq + i,
> > +						    &hv_arm64_msi_irq_chip,
> > +						    domain->host_data);
> > +		if (ret)
> > +			goto free_irq;
> 
> This error path doesn't clean up correctly.  While parent IRQs allocated
> in previous iterations of the loop is cleaned up, the parent IRQ
> allocated in the current iteration is not.
> 

'irq_domain_set_hwirq_and_chip' really shouldn't fail. If you still feel
that we should address this, I can.

> > +
> > +		pr_debug("pID:%d vID:%u\n", (int)(hwirq + i), virq + i);
> > +	}
> > +
> > +	return 0;
> > +
> > +free_irq:
> > +	hv_pci_vec_irq_free(domain, virq, nr_irqs, i);
> > +
> > +	return ret;
> > +}
> > +
> > +/*
> > + * Pick the first online cpu as the irq affinity that can be temporarily used
> > + * for composing MSI from the hypervisor. GIC will eventually set the right
> > + * affinity for the irq and the 'unmask' will retarget the interrupt to that
> > + * cpu.
> > + */
> > +static int hv_pci_vec_irq_domain_activate(struct irq_domain *domain,
> > +					  struct irq_data *irqd, bool reserve)
> > +{
> > +	int cpu = cpumask_first(cpu_online_mask);
> 
> Using the cpu_online_mask may work correctly, though its usage here
> raises a red flag for me.  The problem is that the CPU selected can go offline
> immediately after the above line of code, as the cpus_read_lock() does
> not appear to be held anywhere in the call stack.  If the CPU is only
> a temporary placeholder and will never actually be targeted with the
> interrupt, then maybe the online/offline state doesn't matter.   But if
> that's the case, I'd suggest using the cpu_present_mask instead of the
> cpu_online_mask.  Hyper-V doesn't hot-add CPUs, so cpu_present_mask
> should be stable even if the cpus_read_lock() isn't held, and the code
> doesn't incorrectly imply that it's important for the CPU to be online.
> 
> Michael
> 

Thanks. I can change this to 'cpu_present_mask' in the next iteration.

- Sunil

RE: [PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

[Michael Kelley (LINUX)]

From: Sunil Muthuswamy <sunilmut@microsoft.com> Sent: Tuesday, January 4, 2022 11:24 AM
> 
> On Mon, 27 Dec 2021 17:38:07 +0000,
> "Michael Kelley (LINUX)" <mikelley@microsoft.com> wrote:
> >
> > From: Sunil Muthuswamy <sunilmut@linux.microsoft.com> Sent: Friday,
> > December 17, 2021 10:52 AM
> > >

[snip]

> > > +
> > > +static int hv_pci_vec_irq_domain_alloc(struct irq_domain *domain,
> > > +				       unsigned int virq, unsigned int nr_irqs,
> > > +				       void *args)
> > > +{
> > > +	irq_hw_number_t hwirq;
> > > +	unsigned int i;
> > > +	int ret;
> > > +
> > > +	ret = hv_pci_vec_alloc_device_irq(domain, nr_irqs, &hwirq);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	for (i = 0; i < nr_irqs; i++) {
> > > +		ret = hv_pci_vec_irq_gic_domain_alloc(domain, virq + i,
> > > +						      hwirq + i);
> > > +		if (ret)
> > > +			goto free_irq;
> > > +
> > > +		ret = irq_domain_set_hwirq_and_chip(domain, virq + i,
> > > +						    hwirq + i,
> > > +						    &hv_arm64_msi_irq_chip,
> > > +						    domain->host_data);
> > > +		if (ret)
> > > +			goto free_irq;
> >
> > This error path doesn't clean up correctly.  While parent IRQs allocated
> > in previous iterations of the loop is cleaned up, the parent IRQ
> > allocated in the current iteration is not.
> >
> 
> 'irq_domain_set_hwirq_and_chip' really shouldn't fail. If you still feel
> that we should address this, I can.
> 

My view is that the code should be logically consistent.  If the
error path should never happen, then we can ignore the return value
and not try to do any cleanup.  But if we are going to treat the error
as possible and have cleanup code, then the cleanup code should be
correct.   It looks like the GIC irqchip drivers follow your approach and
assume irq_domain_set_hwirq_and_chip() never fails, so they don't
check the return value.  I would be OK with that approach here.

Michael

Re: [PATCH v7 0/2] PCI: hv: Hyper-V vPCI for arm64

[Marc Zyngier]

On Fri, 17 Dec 2021 18:51:59 +0000,
Sunil Muthuswamy <sunilmut@linux.microsoft.com> wrote:
> 
> From: Sunil Muthuswamy <sunilmut@microsoft.com>
> 
> Current Hyper-V vPCI code only compiles and works for x86. There are some
> hardcoded assumptions about the architectural IRQ chip and other arch
> defines.
> 
> Add support for Hyper-V vPCI for arm64 by first breaking the current hard
> coded dependency using a set of new interfaces and implementing those for
> x86 first. That is in the first patch. The second patch adds support for
> Hyper-V vPCI for arm64 by implementing the above mentioned interfaces. That
> is done by introducing a Hyper-V vPCI specific MSI IRQ domain & chip for
> allocating SPI vectors.

For the series,

Reviewed-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.