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PCI: Enable host bridge emulation for PCI_DOMAINS_GENERIC platforms

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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: Suzuki K Poulose <suzuki.poulose@arm.com>
Closes: http://lore.kernel.org/20250311144601.145736-3-suzuki.poulose@arm.com [2]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Michael 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
This commit is contained in:
Dan Williams 2025-10-24 15:46:21 -07:00 committed by Bjorn Helgaas
parent 3a86608788
commit bcce8c74f1
4 changed files with 46 additions and 55 deletions
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62
drivers/pci/controller/pci-hyperv.c
View File

@ -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 @@ close:
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;

24
drivers/pci/pci.c
View File

@ -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)
{

8
drivers/pci/probe.c
View File

@ -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);
}
@ -1137,7 +1142,8 @@ unregister:
device_del(&bridge->dev);
free:
#ifdef CONFIG_PCI_DOMAINS_GENERIC
pci_bus_release_domain_nr(parent, bus->domain_nr);
if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
pci_bus_release_domain_nr(parent, bus->domain_nr);
#endif
if (bus_registered)
put_device(&bus->dev);

7
include/linux/pci.h
View File

@ -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 */
/*