Commit bcce8c74 authored by Dan Williams's avatar Dan Williams Committed by Bjorn Helgaas
Browse files

PCI: Enable host bridge emulation for PCI_DOMAINS_GENERIC platforms 

The ability to emulate a host bridge is useful not only for hardware PCI
controllers like CONFIG_VMD, or virtual PCI controllers like
CONFIG_PCI_HYPERV, but also for test and development scenarios like
CONFIG_SAMPLES_DEVSEC [1].

One stumbling block for defining CONFIG_SAMPLES_DEVSEC, a sample
implementation of a platform TSM for PCI Device Security, is the need to
accommodate PCI_DOMAINS_GENERIC architectures alongside x86 [2].

In support of supplementing the existing CONFIG_PCI_BRIDGE_EMUL
infrastructure for host bridges:

* Introduce pci_bus_find_emul_domain_nr() as a common way to find a free
  PCI domain number whether that is to reuse the existing dynamic
  allocation code in the !ACPI case, or to assign an unused domain above
  the last ACPI segment.

* Convert pci-hyperv to the new allocator so that the PCI core can
  unconditionally assume that bridge->domain_nr != PCI_DOMAIN_NR_NOT_SET
  is the dynamically allocated case.

A follow on patch can also convert vmd to the new scheme. Currently vmd is
limited to CONFIG_PCI_DOMAINS_GENERIC=n (x86) so, unlike pci-hyperv, it
does not immediately conflict with this new pci_bus_find_emul_domain_nr()
mechanism.

Link: http://lore.kernel.org/174107249038.1288555.12362100502109498455.stgit@dwillia2-xfh.jf.intel.com

 [1]
Reported-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Closes: http://lore.kernel.org/20250311144601.145736-3-suzuki.poulose@arm.com

 [2]
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Tested-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: default avatarMichael Kelley <mhklinux@outlook.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Rob Herring <robh@kernel.org>
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>
Link: https://patch.msgid.link/20251024224622.1470555-2-dan.j.williams@intel.com
parent 3a866087

drivers/pci/controller/pci-hyperv.c

+9 −53
Original line number Diff line number Diff line
@@ -3696,48 +3696,6 @@ static int hv_send_resources_released(struct hv_device *hdev) 
	return 0;

}



#define HVPCI_DOM_MAP_SIZE (64 * 1024)

static DECLARE_BITMAP(hvpci_dom_map, HVPCI_DOM_MAP_SIZE);



/*

 * PCI domain number 0 is used by emulated devices on Gen1 VMs, so define 0

 * as invalid for passthrough PCI devices of this driver.

 */

#define HVPCI_DOM_INVALID 0



/**

 * hv_get_dom_num() - Get a valid PCI domain number

 * Check if the PCI domain number is in use, and return another number if

 * it is in use.

 *

 * @dom: Requested domain number

 *

 * return: domain number on success, HVPCI_DOM_INVALID on failure

 */

static u16 hv_get_dom_num(u16 dom)

{

	unsigned int i;



	if (test_and_set_bit(dom, hvpci_dom_map) == 0)

		return dom;



	for_each_clear_bit(i, hvpci_dom_map, HVPCI_DOM_MAP_SIZE) {

		if (test_and_set_bit(i, hvpci_dom_map) == 0)

			return i;

	}



	return HVPCI_DOM_INVALID;

}



/**

 * hv_put_dom_num() - Mark the PCI domain number as free

 * @dom: Domain number to be freed

 */

static void hv_put_dom_num(u16 dom)

{

	clear_bit(dom, hvpci_dom_map);

}



/**

 * hv_pci_probe() - New VMBus channel probe, for a root PCI bus

 * @hdev:	VMBus's tracking struct for this root PCI bus
@@ -3750,9 +3708,9 @@ static int hv_pci_probe(struct hv_device *hdev, 
{

	struct pci_host_bridge *bridge;

	struct hv_pcibus_device *hbus;

	u16 dom_req, dom;

	int ret, dom;

	u16 dom_req;

	char *name;

	int ret;



	bridge = devm_pci_alloc_host_bridge(&hdev->device, 0);

	if (!bridge)
@@ -3779,11 +3737,14 @@ static int hv_pci_probe(struct hv_device *hdev, 
	 * PCI bus (which is actually emulated by the hypervisor) is domain 0.

	 * (2) There will be no overlap between domains (after fixing possible

	 * collisions) in the same VM.

	 *

	 * Because Gen1 VMs use domain 0, don't allow picking domain 0 here,

	 * even if bytes 4 and 5 of the instance GUID are both zero. For wider

	 * userspace compatibility, limit the domain ID to a 16-bit value.

	 */

	dom_req = hdev->dev_instance.b[5] << 8 | hdev->dev_instance.b[4];

	dom = hv_get_dom_num(dom_req);



	if (dom == HVPCI_DOM_INVALID) {

	dom = pci_bus_find_emul_domain_nr(dom_req, 1, U16_MAX);

	if (dom < 0) {

		dev_err(&hdev->device,

			"Unable to use dom# 0x%x or other numbers", dom_req);

		ret = -EINVAL;
@@ -3917,7 +3878,7 @@ static int hv_pci_probe(struct hv_device *hdev, 
destroy_wq:

	destroy_workqueue(hbus->wq);

free_dom:

	hv_put_dom_num(hbus->bridge->domain_nr);

	pci_bus_release_emul_domain_nr(hbus->bridge->domain_nr);

free_bus:

	kfree(hbus);

	return ret;
@@ -4042,8 +4003,6 @@ static void hv_pci_remove(struct hv_device *hdev) 
	irq_domain_remove(hbus->irq_domain);

	irq_domain_free_fwnode(hbus->fwnode);



	hv_put_dom_num(hbus->bridge->domain_nr);



	kfree(hbus);

}
@@ -4217,9 +4176,6 @@ static int __init init_hv_pci_drv(void) 
	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);



	/* Initialize PCI block r/w interface */

	hvpci_block_ops.read_block = hv_read_config_block;

	hvpci_block_ops.write_block = hv_write_config_block;

drivers/pci/pci.c

+23 −1
Original line number Diff line number Diff line
@@ -6656,9 +6656,31 @@ static void pci_no_domains(void) 
#endif

}



#ifdef CONFIG_PCI_DOMAINS

static DEFINE_IDA(pci_domain_nr_dynamic_ida);



/**

 * pci_bus_find_emul_domain_nr() - allocate a PCI domain number per constraints

 * @hint: desired domain, 0 if any ID in the range of @min to @max is acceptable

 * @min: minimum allowable domain

 * @max: maximum allowable domain, no IDs higher than INT_MAX will be returned

 */

int pci_bus_find_emul_domain_nr(u32 hint, u32 min, u32 max)

{

	return ida_alloc_range(&pci_domain_nr_dynamic_ida, max(hint, min), max,

			       GFP_KERNEL);

}

EXPORT_SYMBOL_GPL(pci_bus_find_emul_domain_nr);



void pci_bus_release_emul_domain_nr(int domain_nr)

{

	ida_free(&pci_domain_nr_dynamic_ida, domain_nr);

}

EXPORT_SYMBOL_GPL(pci_bus_release_emul_domain_nr);

#endif



#ifdef CONFIG_PCI_DOMAINS_GENERIC

static DEFINE_IDA(pci_domain_nr_static_ida);

static DEFINE_IDA(pci_domain_nr_dynamic_ida);



static void of_pci_reserve_static_domain_nr(void)

{

drivers/pci/probe.c

+7 −1
Original line number Diff line number Diff line
@@ -657,6 +657,11 @@ static void pci_release_host_bridge_dev(struct device *dev) 


	pci_free_resource_list(&bridge->windows);

	pci_free_resource_list(&bridge->dma_ranges);



	/* Host bridges only have domain_nr set in the emulation case */

	if (bridge->domain_nr != PCI_DOMAIN_NR_NOT_SET)

		pci_bus_release_emul_domain_nr(bridge->domain_nr);



	kfree(bridge);

}
@@ -1137,6 +1142,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) 
	device_del(&bridge->dev);

free:

#ifdef CONFIG_PCI_DOMAINS_GENERIC

	if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)

		pci_bus_release_domain_nr(parent, bus->domain_nr);

#endif

	if (bus_registered)

include/linux/pci.h

+7 −0
Original line number Diff line number Diff line
@@ -1956,10 +1956,17 @@ DEFINE_GUARD(pci_dev, struct pci_dev *, pci_dev_lock(_T), pci_dev_unlock(_T)) 
 */

#ifdef CONFIG_PCI_DOMAINS

extern int pci_domains_supported;

int pci_bus_find_emul_domain_nr(u32 hint, u32 min, u32 max);

void pci_bus_release_emul_domain_nr(int domain_nr);

#else

enum { pci_domains_supported = 0 };

static inline int pci_domain_nr(struct pci_bus *bus) { return 0; }

static inline int pci_proc_domain(struct pci_bus *bus) { return 0; }

static inline int pci_bus_find_emul_domain_nr(u32 hint, u32 min, u32 max)

{

	return 0;

}

static inline void pci_bus_release_emul_domain_nr(int domain_nr) { }

#endif /* CONFIG_PCI_DOMAINS */



/*