[Skiboot] [PATCH RFC 1/6] core/pci: Add functions to find accessible devices by bdfn
Sergey Miroshnichenko
s.miroshnichenko at yadro.com
Sat Mar 2 01:30:33 AEDT 2019
During the PCIe re-enumeration by an OS the .bdfn field of the struct
pci_device may not correspond to its device's actual address for a while,
so the pci_find_dev() will return an invalid descriptor in this case. Some
code may rely on this behavior, so this patch introduces a new function to
return a descriptor for addressable devices only.
This new function will help in discovering hotplugged devices.
Here's a synthetic (but possible) scenario where pci_find_dev_safe() is
different from pci_find_dev():
I. Before the re-enumeration:
+-[0021:00]---00.0-[01-04]--+-00.0-[02]--
+-01.0-[03]----00.0 Device Z1
+-02.0-[04]--
- pci_find_dev(0021:03:00.0) returns correct struct pci_device *pd for
Device Z1;
- pci_find_dev_safe(0021:03:00.0) returns the same pd.
II. Re-enumeration, step 1:
_____ Dropped the bus numbers by writing zeros
/
+-[0021:00]---00.0-[00-00]--+-00.0-[02]--
+-01.0-[03]----00.0 Device Z1
+-02.0-[04]--
- Device Z1 is unreachable (bus 1 is not assigned), but
pci_find_dev(0021:03:00.0) returns its pd;
- pci_find_dev_safe(0021:03:00.0) returns NULL.
III. Re-enumeration, step 2:
__ Update the bus numbers: primary <- 0,
/ secondary <- 1, subordinate <- ff
/
+-[0021:00]---00.0-[01-ff]--+-00.0-[02]--
+-01.0-[03]----00.0 Device Z1
+-02.0-[04]--
- By coincidence, pci_find_dev(0021:03:00.0) returns pd for Device Z1;
- pci_find_dev_safe(0021:03:00.0) returns pd for Device Z1, which is
correct by coincidence.
IV. Re-enumeration, step 3:
___ Drop the bus numbers
/
+-[0021:00]---00.0-[01-ff]--+-00.0-[00-00]--
+-01.0-[00-00]----00.0 Device Z1
+-02.0-[00-00]--
- Device Z1 is unreachable (downstream 0021:01:01.0 has no bus numbers
assigned), but pci_find_dev(0021:03:00.0) returns its uncorrected pd;
- pci_find_dev_safe(0021:03:00.0) returns NULL.
V. Re-enumeration, step 4:
Set the bus numbers __ _ A phantom of Device Z1
\ / from pci_find_dev(03:00.0)
+-[0021:00]---00.0-[01-ff]--+-00.0-[02-06]-- -
+-01.0-[00-00]----00.0 Device Z1
+-02.0-[00-00]--
- pci_find_dev(0021:03:00.0) returns a phantom of the Device Z1 for wrong
address;
- pci_find_dev_safe(0021:03:00.0) returns NULL.
VI. Re-enumeration, step 5:
+-[0021:00]---00.0-[01-ff]--+-00.0-[02-06]--
-+-01.0-[07-0b]----00.0 Device Z1
/ +-02.0-[00-00]--
Set the bus numbers --
- pci_find_dev(0021:03:00.0) returns a phantom of the Device Z1;
- pci_find_dev_safe(0021:03:00.0) returns NULL;
- pci_find_dev_safe(0021:07:00.0) returns pd for the Device Z1, but its
.bdfn field needs to be corrected (by the following patch).
VI. After the re-enumeration:
+-[0021:00]---00.0-[01-10]--+-00.0-[02-06]--
+-01.0-[07-0b]----00.0 Device Z1
+-02.0-[0c-10]--
Even though the .bdfn field is not correct at the moment, it is clear that
this is a previously known device, not a hotplugged one.
Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko at yadro.com>
---
core/pci.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++
include/pci.h | 2 ++
2 files changed, 85 insertions(+)
diff --git a/core/pci.c b/core/pci.c
index 454b5010..dac4e853 100644
--- a/core/pci.c
+++ b/core/pci.c
@@ -1867,6 +1867,89 @@ struct pci_device *pci_find_dev(struct phb *phb, uint16_t bdfn)
return pci_walk_dev(phb, NULL, __pci_find_dev, &bdfn);
}
+static struct pci_device *__pci_find_parent(struct pci_device *pd, uint8_t bus)
+{
+ struct pci_device *child;
+
+ if (!pd)
+ return NULL;
+
+ if (pd->secondary_bus == bus)
+ return pd;
+
+ if (bus < pd->secondary_bus || bus > pd->subordinate_bus)
+ return NULL;
+
+ list_for_each(&pd->children, child, link) {
+ if (child->secondary_bus == bus)
+ return child;
+ }
+
+ list_for_each(&pd->children, child, link) {
+ struct pci_device *found = __pci_find_parent(child, bus);
+
+ if (found)
+ return found;
+ }
+
+ return NULL;
+}
+
+struct pci_device *pci_find_parent_dev(struct phb *phb, uint16_t bdfn)
+{
+ struct pci_device *pd;
+ uint8_t bus = (bdfn >> 8);
+
+ if (!phb)
+ return NULL;
+
+ list_for_each(&phb->devices, pd, link) {
+ struct pci_device *found = __pci_find_parent(pd, bus);
+
+ if (found)
+ return found;
+ }
+
+ return NULL;
+}
+
+struct pci_device *pci_find_dev_safe(struct phb *phb, uint16_t bdfn)
+{
+ struct pci_device *parent;
+ struct pci_device *child;
+
+ if (!phb)
+ return NULL;
+
+ if (!bdfn) {
+ struct pci_device *pd;
+
+ list_for_each(&phb->devices, pd, link) {
+ if (pd->bdfn == bdfn)
+ return pd;
+ }
+ }
+
+ parent = pci_find_parent_dev(phb, bdfn);
+ if (!parent)
+ return NULL;
+
+ list_for_each(&parent->children, child, link) {
+ if ((child->bdfn & 0xff) == (bdfn & 0xff)) {
+ if (child->bdfn != bdfn) {
+ PCIERR(phb, bdfn, "pci_device has invalid bdfn field %04x:%02x:%02x.%d\n",
+ phb->opal_id,
+ child->bdfn >> 8,
+ (child->bdfn >> 3) & 0x1f,
+ child->bdfn & 0x7);
+ }
+ return child;
+ }
+ }
+
+ return NULL;
+}
+
static int __pci_restore_bridge_buses(struct phb *phb,
struct pci_device *pd,
void *data __unused)
diff --git a/include/pci.h b/include/pci.h
index b49641ca..3262a4bd 100644
--- a/include/pci.h
+++ b/include/pci.h
@@ -473,6 +473,8 @@ extern struct pci_device *pci_walk_dev(struct phb *phb,
void *),
void *userdata);
extern struct pci_device *pci_find_dev(struct phb *phb, uint16_t bdfn);
+extern struct pci_device *pci_find_dev_safe(struct phb *phb, uint16_t bdfn);
+extern struct pci_device *pci_find_parent_dev(struct phb *phb, uint16_t bdfn);
extern void pci_restore_bridge_buses(struct phb *phb, struct pci_device *pd);
extern struct pci_cfg_reg_filter *pci_find_cfg_reg_filter(struct pci_device *pd,
uint32_t start, uint32_t len);
--
2.20.1
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