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PCI: vmd: Switch to pci_bus_find_emul_domain_nr() 

The new common domain number allocator can replace the custom allocator
in VMD.

Beyond some code reuse benefits it does close a potential race whereby
vmd_find_free_domain() collides with new PCI buses coming online with a
conflicting domain number. Such a race has not been observed in practice,
hence not tagging this change as a fix.

As VMD uses pci_create_root_bus() rather than pci_alloc_host_bridge() +
pci_scan_root_bus_bridge() it has no chance to set ->domain_nr in the
bridge so needs to manage freeing the domain number on its own.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Szymon Durawa <szymon.durawa@linux.intel.com>
Cc: Nirmal Patel <nirmal.patel@linux.intel.com>
Link: https://patch.msgid.link/20251024224622.1470555-3-dan.j.williams@intel.com
This commit is contained in:
Dan Williams 2025-10-24 15:46:22 -07:00 committed by Bjorn Helgaas
parent bcce8c74f1
commit b37b6095a9
1 changed files with 17 additions and 23 deletions
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40
drivers/pci/controller/vmd.c
View File

@ -565,22 +565,6 @@ static void vmd_detach_resources(struct vmd_dev *vmd)
vmd->dev->resource[VMD_MEMBAR2].child = NULL;
}
/*
* VMD 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.
*/
static int vmd_find_free_domain(void)
{
int domain = 0xffff;
struct pci_bus *bus = NULL;
while ((bus = pci_find_next_bus(bus)) != NULL)
domain = max_t(int, domain, pci_domain_nr(bus));
return domain + 1;
}
static int vmd_get_phys_offsets(struct vmd_dev *vmd, bool native_hint,
resource_size_t *offset1,
resource_size_t *offset2)
@ -865,13 +849,6 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
.parent = res,
};
sd->vmd_dev = vmd->dev;
sd->domain = vmd_find_free_domain();
if (sd->domain < 0)
return sd->domain;
sd->node = pcibus_to_node(vmd->dev->bus);
/*
* Currently MSI remapping must be enabled in guest passthrough mode
* due to some missing interrupt remapping plumbing. This is probably
@ -897,9 +874,24 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
pci_add_resource_offset(&resources, &vmd->resources[1], offset[0]);
pci_add_resource_offset(&resources, &vmd->resources[2], offset[1]);
sd->vmd_dev = vmd->dev;
/*
* 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.
*/
sd->domain = pci_bus_find_emul_domain_nr(0, 0x10000, INT_MAX);
if (sd->domain < 0)
return sd->domain;
sd->node = pcibus_to_node(vmd->dev->bus);
vmd->bus = pci_create_root_bus(&vmd->dev->dev, vmd->busn_start,
&vmd_ops, sd, &resources);
if (!vmd->bus) {
pci_bus_release_emul_domain_nr(sd->domain);
pci_free_resource_list(&resources);
vmd_remove_irq_domain(vmd);
return -ENODEV;
@ -992,6 +984,7 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
return -ENOMEM;
vmd->dev = dev;
vmd->sysdata.domain = PCI_DOMAIN_NR_NOT_SET;
vmd->instance = ida_alloc(&vmd_instance_ida, GFP_KERNEL);
if (vmd->instance < 0)
return vmd->instance;
@ -1057,6 +1050,7 @@ static void vmd_remove(struct pci_dev *dev)
vmd_detach_resources(vmd);
vmd_remove_irq_domain(vmd);
ida_free(&vmd_instance_ida, vmd->instance);
pci_bus_release_emul_domain_nr(vmd->sysdata.domain);
}
static void vmd_shutdown(struct pci_dev *dev)