[RFC PATCH v2] PCI: hv: Avoid the retarget interrupt hypercall in irq_unmask() on ARM64

[Boqun Feng]

On ARM64 Hyper-V guests, SPIs are used for the interrupts of virtual PCI
devices, and SPIs can be managed directly via GICD registers. Therefore
the retarget interrupt hypercall is not needed on ARM64.

An arch-specific interface hv_arch_irq_unmask() is introduced to handle
the architecture level differences on this. For x86, the behavior
remains unchanged, while for ARM64 no hypercall is invoked when
unmasking an irq for virtual PCI devices.

Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
---
v1 -> v2:

*	Introduce arch-specific interface hv_arch_irq_unmask() as
	suggested by Bjorn

 drivers/pci/controller/pci-hyperv.c | 233 +++++++++++++++-------------
 1 file changed, 122 insertions(+), 111 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 20ea2ee330b8..2a1481a52489 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -616,6 +616,121 @@ static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
 {
 	return pci_msi_prepare(domain, dev, nvec, info);
 }
+
+/**
+ * hv_arch_irq_unmask() - "Unmask" the IRQ by setting its current
+ * affinity.
+ * @data:	Describes the IRQ
+ *
+ * Build new a destination for the MSI and make a hypercall to
+ * update the Interrupt Redirection Table. "Device Logical ID"
+ * is built out of this PCI bus's instance GUID and the function
+ * number of the device.
+ */
+static void hv_arch_irq_unmask(struct irq_data *data)
+{
+	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
+	struct hv_retarget_device_interrupt *params;
+	struct hv_pcibus_device *hbus;
+	struct cpumask *dest;
+	cpumask_var_t tmp;
+	struct pci_bus *pbus;
+	struct pci_dev *pdev;
+	unsigned long flags;
+	u32 var_size = 0;
+	int cpu, nr_bank;
+	u64 res;
+
+	dest = irq_data_get_effective_affinity_mask(data);
+	pdev = msi_desc_to_pci_dev(msi_desc);
+	pbus = pdev->bus;
+	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
+
+	spin_lock_irqsave(&hbus->retarget_msi_interrupt_lock, flags);
+
+	params = &hbus->retarget_msi_interrupt_params;
+	memset(params, 0, sizeof(*params));
+	params->partition_id = HV_PARTITION_ID_SELF;
+	params->int_entry.source = HV_INTERRUPT_SOURCE_MSI;
+	hv_set_msi_entry_from_desc(&params->int_entry.msi_entry, msi_desc);
+	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
+			   (hbus->hdev->dev_instance.b[4] << 16) |
+			   (hbus->hdev->dev_instance.b[7] << 8) |
+			   (hbus->hdev->dev_instance.b[6] & 0xf8) |
+			   PCI_FUNC(pdev->devfn);
+	params->int_target.vector = hv_msi_get_int_vector(data);
+
+	/*
+	 * Honoring apic->delivery_mode set to APIC_DELIVERY_MODE_FIXED by
+	 * setting the HV_DEVICE_INTERRUPT_TARGET_MULTICAST flag results in a
+	 * spurious interrupt storm. Not doing so does not seem to have a
+	 * negative effect (yet?).
+	 */
+
+	if (hbus->protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
+		/*
+		 * PCI_PROTOCOL_VERSION_1_2 supports the VP_SET version of the
+		 * HVCALL_RETARGET_INTERRUPT hypercall, which also coincides
+		 * with >64 VP support.
+		 * ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED
+		 * is not sufficient for this hypercall.
+		 */
+		params->int_target.flags |=
+			HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET;
+
+		if (!alloc_cpumask_var(&tmp, GFP_ATOMIC)) {
+			res = 1;
+			goto exit_unlock;
+		}
+
+		cpumask_and(tmp, dest, cpu_online_mask);
+		nr_bank = cpumask_to_vpset(&params->int_target.vp_set, tmp);
+		free_cpumask_var(tmp);
+
+		if (nr_bank <= 0) {
+			res = 1;
+			goto exit_unlock;
+		}
+
+		/*
+		 * var-sized hypercall, var-size starts after vp_mask (thus
+		 * vp_set.format does not count, but vp_set.valid_bank_mask
+		 * does).
+		 */
+		var_size = 1 + nr_bank;
+	} else {
+		for_each_cpu_and(cpu, dest, cpu_online_mask) {
+			params->int_target.vp_mask |=
+				(1ULL << hv_cpu_number_to_vp_number(cpu));
+		}
+	}
+
+	res = hv_do_hypercall(HVCALL_RETARGET_INTERRUPT | (var_size << 17),
+			      params, NULL);
+
+exit_unlock:
+	spin_unlock_irqrestore(&hbus->retarget_msi_interrupt_lock, flags);
+
+	/*
+	 * During hibernation, when a CPU is offlined, the kernel tries
+	 * to move the interrupt to the remaining CPUs that haven't
+	 * been offlined yet. In this case, the below hv_do_hypercall()
+	 * always fails since the vmbus channel has been closed:
+	 * refer to cpu_disable_common() -> fixup_irqs() ->
+	 * irq_migrate_all_off_this_cpu() -> migrate_one_irq().
+	 *
+	 * Suppress the error message for hibernation because the failure
+	 * during hibernation does not matter (at this time all the devices
+	 * have been frozen). Note: the correct affinity info is still updated
+	 * into the irqdata data structure in migrate_one_irq() ->
+	 * irq_do_set_affinity() -> hv_set_affinity(), so later when the VM
+	 * resumes, hv_pci_restore_msi_state() is able to correctly restore
+	 * the interrupt with the correct affinity.
+	 */
+	if (!hv_result_success(res) && hbus->state != hv_pcibus_removing)
+		dev_err(&hbus->hdev->device,
+			"%s() failed: %#llx", __func__, res);
+}
 #elif defined(CONFIG_ARM64)
 /*
  * SPI vectors to use for vPCI; arch SPIs range is [32, 1019], but leaving a bit
@@ -839,6 +954,12 @@ static struct irq_domain *hv_pci_get_root_domain(void)
 {
 	return hv_msi_gic_irq_domain;
 }
+
+/*
+ * SPIs are used for interrupts of PCI devices and SPIs is managed via GICD
+ * registers which Hyper-V already supports, so no hypercall needed.
+ */
+static void hv_arch_irq_unmask(struct irq_data *data) { }
 #endif /* CONFIG_ARM64 */
 
 /**
@@ -1456,119 +1577,9 @@ static void hv_irq_mask(struct irq_data *data)
 		irq_chip_mask_parent(data);
 }
 
-/**
- * hv_irq_unmask() - "Unmask" the IRQ by setting its current
- * affinity.
- * @data:	Describes the IRQ
- *
- * Build new a destination for the MSI and make a hypercall to
- * update the Interrupt Redirection Table. "Device Logical ID"
- * is built out of this PCI bus's instance GUID and the function
- * number of the device.
- */
 static void hv_irq_unmask(struct irq_data *data)
 {
-	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
-	struct hv_retarget_device_interrupt *params;
-	struct hv_pcibus_device *hbus;
-	struct cpumask *dest;
-	cpumask_var_t tmp;
-	struct pci_bus *pbus;
-	struct pci_dev *pdev;
-	unsigned long flags;
-	u32 var_size = 0;
-	int cpu, nr_bank;
-	u64 res;
-
-	dest = irq_data_get_effective_affinity_mask(data);
-	pdev = msi_desc_to_pci_dev(msi_desc);
-	pbus = pdev->bus;
-	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
-
-	spin_lock_irqsave(&hbus->retarget_msi_interrupt_lock, flags);
-
-	params = &hbus->retarget_msi_interrupt_params;
-	memset(params, 0, sizeof(*params));
-	params->partition_id = HV_PARTITION_ID_SELF;
-	params->int_entry.source = HV_INTERRUPT_SOURCE_MSI;
-	hv_set_msi_entry_from_desc(&params->int_entry.msi_entry, msi_desc);
-	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
-			   (hbus->hdev->dev_instance.b[4] << 16) |
-			   (hbus->hdev->dev_instance.b[7] << 8) |
-			   (hbus->hdev->dev_instance.b[6] & 0xf8) |
-			   PCI_FUNC(pdev->devfn);
-	params->int_target.vector = hv_msi_get_int_vector(data);
-
-	/*
-	 * Honoring apic->delivery_mode set to APIC_DELIVERY_MODE_FIXED by
-	 * setting the HV_DEVICE_INTERRUPT_TARGET_MULTICAST flag results in a
-	 * spurious interrupt storm. Not doing so does not seem to have a
-	 * negative effect (yet?).
-	 */
-
-	if (hbus->protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
-		/*
-		 * PCI_PROTOCOL_VERSION_1_2 supports the VP_SET version of the
-		 * HVCALL_RETARGET_INTERRUPT hypercall, which also coincides
-		 * with >64 VP support.
-		 * ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED
-		 * is not sufficient for this hypercall.
-		 */
-		params->int_target.flags |=
-			HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET;
-
-		if (!alloc_cpumask_var(&tmp, GFP_ATOMIC)) {
-			res = 1;
-			goto exit_unlock;
-		}
-
-		cpumask_and(tmp, dest, cpu_online_mask);
-		nr_bank = cpumask_to_vpset(&params->int_target.vp_set, tmp);
-		free_cpumask_var(tmp);
-
-		if (nr_bank <= 0) {
-			res = 1;
-			goto exit_unlock;
-		}
-
-		/*
-		 * var-sized hypercall, var-size starts after vp_mask (thus
-		 * vp_set.format does not count, but vp_set.valid_bank_mask
-		 * does).
-		 */
-		var_size = 1 + nr_bank;
-	} else {
-		for_each_cpu_and(cpu, dest, cpu_online_mask) {
-			params->int_target.vp_mask |=
-				(1ULL << hv_cpu_number_to_vp_number(cpu));
-		}
-	}
-
-	res = hv_do_hypercall(HVCALL_RETARGET_INTERRUPT | (var_size << 17),
-			      params, NULL);
-
-exit_unlock:
-	spin_unlock_irqrestore(&hbus->retarget_msi_interrupt_lock, flags);
-
-	/*
-	 * During hibernation, when a CPU is offlined, the kernel tries
-	 * to move the interrupt to the remaining CPUs that haven't
-	 * been offlined yet. In this case, the below hv_do_hypercall()
-	 * always fails since the vmbus channel has been closed:
-	 * refer to cpu_disable_common() -> fixup_irqs() ->
-	 * irq_migrate_all_off_this_cpu() -> migrate_one_irq().
-	 *
-	 * Suppress the error message for hibernation because the failure
-	 * during hibernation does not matter (at this time all the devices
-	 * have been frozen). Note: the correct affinity info is still updated
-	 * into the irqdata data structure in migrate_one_irq() ->
-	 * irq_do_set_affinity() -> hv_set_affinity(), so later when the VM
-	 * resumes, hv_pci_restore_msi_state() is able to correctly restore
-	 * the interrupt with the correct affinity.
-	 */
-	if (!hv_result_success(res) && hbus->state != hv_pcibus_removing)
-		dev_err(&hbus->hdev->device,
-			"%s() failed: %#llx", __func__, res);
+	hv_arch_irq_unmask(data);
 
 	if (data->parent_data->chip->irq_unmask)
 		irq_chip_unmask_parent(data);
-- 
2.35.1