Message-ID: <MWHPR21MB1593272A454D568311C3B254D7429@MWHPR21MB1593.namprd21.prod.outlook.com>
Date:   Mon, 27 Dec 2021 17:38:07 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Sunil Muthuswamy <sunilmut@...ux.microsoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "maz@...nel.org" <maz@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>
Subject: RE: [PATCH v7 2/2] PCI: hv: Add arm64 Hyper-V vPCI support

From: Sunil Muthuswamy <sunilmut@...ux.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@...rosoft.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
> 

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