RE: [PATCH 14/16] PCI: hv: Switch to msi_create_parent_irq_domain()

Michael Kelley
2025-07-03T21:14:22Z

From: Nam Cao <namcao@linutronix.de> Sent: Thursday, June 26, 2025 7:48 AM
>
> Move away from the legacy MSI domain setup, switch to use
> msi_create_parent_irq_domain().

From a build standpoint, this patch does not apply cleanly to
linux-next20250630. See also an issue below where a needed irq
function isn't exported.

At runtime, I've done basic smoke testing on an x86 VM in the Azure
cloud that has a Mellanox NIC VF and two NVMe devices as PCI devices.
So far everything looks good. But I'm still doing additional testing, and
I want to also test on an ARM64 VM. Please give me another day or two
to be completely satisfied.

Michael Kelley

>
> Signed-off-by: Nam Cao <namcao@linutronix.de>
> ---
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Wei Liu <wei.liu@kernel.org>
> Cc: Dexuan Cui <decui@microsoft.com>
> Cc: linux-hyperv@vger.kernel.org
> ---
> drivers/pci/Kconfig | 1 +
> drivers/pci/controller/pci-hyperv.c | 98 +++++++++++++++++++++++------
> 2 files changed, 80 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 9c0e4aaf4e8cb..9a249c65aedcd 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -223,6 +223,7 @@ config PCI_HYPERV
> tristate "Hyper-V PCI Frontend"
> depends on ((X86 && X86_64) || ARM64) && HYPERV && PCI_MSI && SYSFS
> select PCI_HYPERV_INTERFACE
> + select IRQ_MSI_LIB
> help
> The PCI device frontend driver allows the kernel to import arbitrary
> PCI devices from a PCI backend to support PCI driver domains.
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index ef5d655a0052c..3a24fadddb83b 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -44,6 +44,7 @@
> #include <linux/delay.h>
> #include <linux/semaphore.h>
> #include <linux/irq.h>
> +#include <linux/irqchip/irq-msi-lib.h>
> #include <linux/msi.h>
> #include <linux/hyperv.h>
> #include <linux/refcount.h>
> @@ -508,7 +509,6 @@ struct hv_pcibus_device {
> struct list_head children;
> struct list_head dr_list;
>
> - struct msi_domain_info msi_info;
> struct irq_domain *irq_domain;
>
> struct workqueue_struct *wq;
> @@ -1687,7 +1687,7 @@ static void hv_msi_free(struct irq_domain *domain, struct msi_domain_info *info,
> struct msi_desc *msi = irq_data_get_msi_desc(irq_data);
>
> pdev = msi_desc_to_pci_dev(msi);
> - hbus = info->data;
> + hbus = domain->host_data;
> int_desc = irq_data_get_irq_chip_data(irq_data);
> if (!int_desc)
> return;
> @@ -1705,7 +1705,6 @@ 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);
> }
> @@ -1716,7 +1715,6 @@ static void hv_irq_unmask(struct irq_data *data)
>
> if (data->parent_data->chip->irq_unmask)
> irq_chip_unmask_parent(data);
> - pci_msi_unmask_irq(data);
> }
>
> struct compose_comp_ctxt {
> @@ -2101,6 +2099,44 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
> msg->data = 0;
> }
>
> +static bool hv_pcie_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
> + struct irq_domain *real_parent, struct msi_domain_info *info)
> +{
> + struct irq_chip *chip = info->chip;
> +
> + if (!msi_lib_init_dev_msi_info(dev, domain, real_parent, info))
> + return false;
> +
> + info->ops->msi_prepare = hv_msi_prepare;
> +
> + chip->irq_set_affinity = irq_chip_set_affinity_parent;
> +
> + if (IS_ENABLED(CONFIG_X86))
> + chip->flags |= IRQCHIP_MOVE_DEFERRED;
> +
> + return true;
> +}
> +
> +#define HV_PCIE_MSI_FLAGS_REQUIRED (MSI_FLAG_USE_DEF_DOM_OPS
> | \
> + MSI_FLAG_USE_DEF_CHIP_OPS | \
> + MSI_FLAG_PCI_MSI_MASK_PARENT)
> +#define HV_PCIE_MSI_FLAGS_SUPPORTED (MSI_FLAG_MULTI_PCI_MSI
> | \
> + MSI_FLAG_PCI_MSIX | \
> + MSI_GENERIC_FLAGS_MASK)
> +
> +static const struct msi_parent_ops hv_pcie_msi_parent_ops = {
> + .required_flags = HV_PCIE_MSI_FLAGS_REQUIRED,
> + .supported_flags = HV_PCIE_MSI_FLAGS_SUPPORTED,
> + .bus_select_token = DOMAIN_BUS_PCI_MSI,
> +#ifdef CONFIG_X86
> + .chip_flags = MSI_CHIP_FLAG_SET_ACK,
> +#elif defined(CONFIG_ARM64)
> + .chip_flags = MSI_CHIP_FLAG_SET_EOI,
> +#endif
> + .prefix = "HV-",
> + .init_dev_msi_info = hv_pcie_init_dev_msi_info,
> +};
> +
> /* HW Interrupt Chip Descriptor */
> static struct irq_chip hv_msi_irq_chip = {
> .name = "Hyper-V PCIe MSI",
> @@ -2108,7 +2144,6 @@ static struct irq_chip hv_msi_irq_chip = {
> .irq_set_affinity = irq_chip_set_affinity_parent,
> #ifdef CONFIG_X86
> .irq_ack = irq_chip_ack_parent,
> - .flags = IRQCHIP_MOVE_DEFERRED,
> #elif defined(CONFIG_ARM64)
> .irq_eoi = irq_chip_eoi_parent,
> #endif
> @@ -2116,9 +2151,37 @@ static struct irq_chip hv_msi_irq_chip = {
> .irq_unmask = hv_irq_unmask,
> };
>
> -static struct msi_domain_ops hv_msi_ops = {
> - .msi_prepare = hv_msi_prepare,
> - .msi_free = hv_msi_free,
> +static int hv_pcie_domain_alloc(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs,
> + void *arg)
> +{
> + /* TODO: move the content of hv_compose_msi_msg() in here */
> + int ret;
> +
> + ret = irq_domain_alloc_irqs_parent(d, virq, nr_irqs, arg);
> + if (ret < 0)
> + return ret;
> +
> + for (int i = 0; i < nr_irqs; i++) {
> + irq_domain_set_info(d, virq + i, 0, &hv_msi_irq_chip, NULL, FLOW_HANDLER, NULL,
> + FLOW_NAME);
> + }
> +
> + return 0;
> +}
> +
> +static void hv_pcie_domain_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
> +{
> + struct msi_domain_info *info = d->host_data;
> +
> + for (int i = 0; i < nr_irqs; i++)
> + hv_msi_free(d, info, virq + i);
> +
> + irq_domain_free_irqs_top(d, virq, nr_irqs);

This code can be built as a module, so irq_domain_free_irqs_top() needs to be
exported, which it currently is not.

> +}
> +
> +static const struct irq_domain_ops hv_pcie_domain_ops = {
> + .alloc = hv_pcie_domain_alloc,
> + .free = hv_pcie_domain_free,
> };
>
> /**
> @@ -2136,17 +2199,14 @@ static struct msi_domain_ops hv_msi_ops = {
> */
> static int hv_pcie_init_irq_domain(struct hv_pcibus_device *hbus)
> {
> - hbus->msi_info.chip = &hv_msi_irq_chip;
> - hbus->msi_info.ops = &hv_msi_ops;
> - 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 = 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,
> - hv_pci_get_root_domain());
> + struct irq_domain_info info = {
> + .fwnode = hbus->fwnode,
> + .ops = &hv_pcie_domain_ops,
> + .host_data = hbus,
> + .parent = hv_pci_get_root_domain(),
> + };
> +
> + hbus->irq_domain = msi_create_parent_irq_domain(&info, &hv_pcie_msi_parent_ops);
> if (!hbus->irq_domain) {
> dev_err(&hbus->hdev->device,
> "Failed to build an MSI IRQ domain\n");
> --
> 2.39.5
>