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Message-ID: <20250716160835.680486-3-dan.j.williams@intel.com>
Date: Wed, 16 Jul 2025 09:08:34 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <lukas@...ner.de>,
<linux-kernel@...r.kernel.org>, <Jonathan.Cameron@...wei.com>, "Suzuki K
Poulose" <suzuki.poulose@....com>, Lorenzo Pieralisi <lpieralisi@...nel.org>,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Rob Herring
<robh@...nel.org>, "K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang
<haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
<decui@...rosoft.com>
Subject: [PATCH 2/3] 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: Suzuki K Poulose <suzuki.poulose@....com>
Closes: http://lore.kernel.org/20250311144601.145736-3-suzuki.poulose@arm.com
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Rob Herring <robh@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Wei Liu <wei.liu@...nel.org>
Cc: Dexuan Cui <decui@...rosoft.com>
Tested-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
drivers/pci/controller/pci-hyperv.c | 53 ++---------------------------
drivers/pci/pci.c | 43 ++++++++++++++++++++++-
drivers/pci/probe.c | 8 ++++-
include/linux/pci.h | 4 +++
4 files changed, 56 insertions(+), 52 deletions(-)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index ef5d655a0052..cfe9806bdbe4 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -3630,48 +3630,6 @@ 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
@@ -3715,9 +3673,9 @@ static int hv_pci_probe(struct hv_device *hdev,
* collisions) in the same VM.
*/
dom_req = hdev->dev_instance.b[5] << 8 | hdev->dev_instance.b[4];
- dom = hv_get_dom_num(dom_req);
+ dom = pci_bus_find_emul_domain_nr(dom_req);
- if (dom == HVPCI_DOM_INVALID) {
+ if (dom < 0) {
dev_err(&hdev->device,
"Unable to use dom# 0x%x or other numbers", dom_req);
ret = -EINVAL;
@@ -3851,7 +3809,7 @@ 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;
@@ -3976,8 +3934,6 @@ 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);
}
@@ -4148,9 +4104,6 @@ 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;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e9448d55113b..833ebf2d5213 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6692,9 +6692,50 @@ static void pci_no_domains(void)
#endif
}
+#ifdef CONFIG_PCI_DOMAINS
+static DEFINE_IDA(pci_domain_nr_dynamic_ida);
+
+/*
+ * Find a free domain_nr either allocated by pci_domain_nr_dynamic_ida or
+ * fallback to the first free domain number above the last ACPI segment number.
+ * Caller may have a specific domain number in mind, in which case try to
+ * reserve it.
+ *
+ * Note that this allocation is freed by pci_release_host_bridge_dev().
+ */
+int pci_bus_find_emul_domain_nr(int hint)
+{
+ if (hint >= 0) {
+ hint = ida_alloc_range(&pci_domain_nr_dynamic_ida, hint, hint,
+ GFP_KERNEL);
+
+ if (hint >= 0)
+ return hint;
+ }
+
+ if (acpi_disabled)
+ return ida_alloc(&pci_domain_nr_dynamic_ida, GFP_KERNEL);
+
+ /*
+ * Emulated domains start at 0x10000 to not clash with ACPI _SEG
+ * domains. Per ACPI r6.0, sec 6.5.6, _SEG returns an integer, of
+ * which the lower 16 bits are the PCI Segment Group (domain) number.
+ * Other bits are currently reserved.
+ */
+ return ida_alloc_range(&pci_domain_nr_dynamic_ida, 0x10000, INT_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)
{
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 4b8693ec9e4c..e94978c3be3d 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -632,6 +632,11 @@ 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);
}
@@ -1112,7 +1117,8 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
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);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 05e68f35f392..f6a713da5c49 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1934,10 +1934,14 @@ 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(int hint);
+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(int hint) { return 0; }
+static inline void pci_bus_release_emul_domain_nr(int domain_nr) { }
#endif /* CONFIG_PCI_DOMAINS */
/*
--
2.50.1
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