On Mon, 27 Dec 2021 17:38:07 +0000,
"Michael Kelley (LINUX)" [off-list ref] wrote:

From: Sunil Muthuswamy <redacted> Sent: Friday, December 17, 2021 10:52 AM

quoted

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 <redacted>
---
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.