PCI : bridge resource reallocation patchset -- followup

During test busn_res allocation with cardbus, found pci card removal is not working anymore, and it turns out it is broken by:

|commit 79cc9601c3e42b4f0650fe7e69132ebce7ab48f9
|Date:   Tue Nov 22 21:06:53 2011 -0800
|
|    PCI: Only call pci_stop_bus_device() one time for child devices at remove

that patch changed pci_remove_behind_bridge behavoir that yenta_carbus depends.

Restore the old behavoir of pci_remove_behind_bridge by:
1. rename pci_remove_behind_bridge to __pci_remove_behind_bridge, and let __pci_remove_bus_device() call it instead.
2. add pci-stop_befind_bridge that will stop device under bridge
3. add back pci_remove_behind_bridge that will stop and remove device under bridge.

This one is for v3.3

During recent strick checking about sysfs_remove from Eric. it will spit more bitter warning.

For SRIOV hotplug, we are calling pci_stop_dev() for VF at first. (after we update pci_stop_bus_devices).

that pci_stop_dev will calling device_unregiste for that VF, so that directory in VF is removed already.

We double checking if that VF dir in /sys is there, before try removing that
physfn link.

Signed-of-by Yinghai Lu <[email protected]>

---
 drivers/pci/iov.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

drivers/pci/iov.c +0 -0

index 0321fa3..dfc7d65 100644
@@ -173,7 +173,12 @@ static void virtfn_remove(struct pci_dev *dev, int id, int reset)
 
 	sprintf(buf, "virtfn%u", id);
 	sysfs_remove_link(&dev->dev.kobj, buf);

Some BIOS enable both pref for MEM0 and MEM1.

but we assume MEM1 is non-pref...

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +1 -0

index 090217a..d5897c3 100644
@@ -914,6 +914,14 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
 	if (realloc_head)
 		add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size, 0 /* dont care */);
 
+	/* MEM1 must not be pref mmio */

Quoted 17 lines · On Sat,  4 Feb 2012 22:55:02 -0800 Yinghai Lu <[email protected]> wrote:

Some BIOS enable both pref for MEM0 and MEM1.

but we assume MEM1 is non-pref...

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |    8 ++++++++

 1 files changed, 8 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +0 -0

index 090217a..d5897c3 100644
@@ -914,6 +914,14 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
       if (realloc_head)
               add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size, 0 /* dont care */);
 

drivers/pci/setup-bus.c static void pci_bus_size_cardbus(struct pci_bus *bus, · line 927

Quoted 11 lines

drivers/pci/setup-bus.c +8 -0

+     /* MEM1 must not be pref mmio */
+     pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);
+     if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM1) {
+             ctrl &= ~PCI_CB_BRIDGE_CTL_PREFETCH_MEM1;
+             pci_write_config_word(bridge, PCI_CB_BRIDGE_CONTROL, ctrl);
+             pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);
+     }
+
       /*
        * Check whether prefetchable memory is supported
        * by this bridge.

Does this actually fix any bugs?

Dominik, have you tested it?

Quoted 20 lines · Jesse Barnes

Quoted 17 lines · On Sat,  4 Feb 2012 22:55:02 -0800 Yinghai Lu <[email protected]> wrote:

Some BIOS enable both pref for MEM0 and MEM1.

but we assume MEM1 is non-pref...

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |    8 ++++++++

 1 files changed, 8 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +0 -0

index 090217a..d5897c3 100644
@@ -914,6 +914,14 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
       if (realloc_head)
               add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size, 0 /* dont care */);
 

Quoted 13 lines

drivers/pci/setup-bus.c static void pci_bus_size_cardbus(struct pci_bus *bus, · line 927

Quoted 11 lines

drivers/pci/setup-bus.c +8 -0

+     /* MEM1 must not be pref mmio */
+     pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);
+     if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM1) {
+             ctrl &= ~PCI_CB_BRIDGE_CTL_PREFETCH_MEM1;
+             pci_write_config_word(bridge, PCI_CB_BRIDGE_CONTROL, ctrl);
+             pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);
+     }
+
       /*
        * Check whether prefetchable memory is supported
        * by this bridge.

Does this actually fix any bugs?

at least, one of laptop have this problem.

We should not set the requested size to -2.

that will confuse the resource list sorting with align when SIZEALIGN is used.

Change to STARTALIGN and pass align from start.

We are safe to do that just as we do that regular pci bridge.

In the long run, we should just treat cardbus like regular pci bridge.

Also fix when realloc is not passed, should keep the requested size.

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |   63 ++++++++++++++++++++++++++--------------------
 1 files changed, 36 insertions(+), 27 deletions(-)

drivers/pci/setup-bus.c +21 -12

index d5897c3..3b3932a 100644
@@ -898,21 +898,30 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
 {
 	struct pci_dev *bridge = bus->self;
 	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
+	resource_size_t b_res_3_size = pci_cardbus_mem_size * 2;
 	u16 ctrl;
 
 	/*
 	 * Reserve some resources for CardBus.  We reserve
 	 * a fixed amount of bus space for CardBus bridges.
 	 */
-	b_res[0].start = 0;
-	b_res[0].flags |= IORESOURCE_IO | IORESOURCE_SIZEALIGN;
-	if (realloc_head)
-		add_to_list(realloc_head, bridge, b_res, pci_cardbus_io_size, 0 /* dont care */);
+	b_res[0].start = pci_cardbus_io_size;
+	b_res[0].end = b_res[0].start + pci_cardbus_io_size - 1;
+	b_res[0].flags |= IORESOURCE_IO | IORESOURCE_STARTALIGN;
+	if (realloc_head) {
+		b_res[0].end -= pci_cardbus_io_size;
+		add_to_list(realloc_head, bridge, b_res, pci_cardbus_io_size,
+				pci_cardbus_io_size);
+	}
 
-	b_res[1].start = 0;
-	b_res[1].flags |= IORESOURCE_IO | IORESOURCE_SIZEALIGN;
-	if (realloc_head)
-		add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size, 0 /* dont care */);
+	b_res[1].start = pci_cardbus_io_size;
+	b_res[1].end = b_res[1].start + pci_cardbus_io_size - 1;
+	b_res[1].flags |= IORESOURCE_IO | IORESOURCE_STARTALIGN;
+	if (realloc_head) {
+		b_res[1].end -= pci_cardbus_io_size;
+		add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size,
+				 pci_cardbus_io_size);
+	}
 
 	/* MEM1 must not be pref mmio */
 	pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);

@@ -939,28 +948,28 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
 	 * twice the size.
 	 */
 	if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM0) {
-		b_res[2].start = 0;
-		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH | IORESOURCE_SIZEALIGN;
-		if (realloc_head)
-			add_to_list(realloc_head, bridge, b_res+2, pci_cardbus_mem_size, 0 /* dont care */);
+		b_res[2].start = pci_cardbus_mem_size;
+		b_res[2].end = b_res[2].start + pci_cardbus_mem_size - 1;
+		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH |
+				  IORESOURCE_STARTALIGN;

drivers/pci/setup-bus.c +8 -6

 	}
 
-	/* set the size of the resource to zero, so that the resource does not
-	 * get assigned during required-resource allocation cycle but gets assigned
-	 * during the optional-resource allocation cycle.
- 	 */
-	b_res[0].start = b_res[1].start = b_res[2].start = b_res[3].start = 1;
-	b_res[0].end = b_res[1].end = b_res[2].end = b_res[3].end = 0;
+	b_res[3].start = pci_cardbus_mem_size;
+	b_res[3].end = b_res[3].start + b_res_3_size - 1;
+	b_res[3].flags |= IORESOURCE_MEM | IORESOURCE_STARTALIGN;
+	if (realloc_head) {
+		b_res[3].end -= b_res_3_size;
+		add_to_list(realloc_head, bridge, b_res+3, b_res_3_size,
+				 pci_cardbus_mem_size);
+	}
 }
 
 void __ref __pci_bus_size_bridges(struct pci_bus *bus,

Signature · 1 line

1.7.7

Quoted 72 lines · Yinghai Lu

We should not set the requested size to -2.

that will confuse the resource list sorting with align when SIZEALIGN is used.

Change to STARTALIGN and pass align from start.

We are safe to do that just as we do that regular pci bridge.

In the long run, we should just treat cardbus like regular pci bridge.

Also fix when realloc is not passed, should keep the requested size.

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |   63 ++++++++++++++++++++++++++--------------------

 1 files changed, 36 insertions(+), 27 deletions(-)

drivers/pci/setup-bus.c +21 -12

index d5897c3..3b3932a 100644
@@ -898,21 +898,30 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
  {
       struct pci_dev *bridge = bus->self;
       struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
+     resource_size_t b_res_3_size = pci_cardbus_mem_size * 2;
       u16 ctrl;
 
       /*
        * Reserve some resources for CardBus.  We reserve
        * a fixed amount of bus space for CardBus bridges.
        */
-     b_res[0].start = 0;
-     b_res[0].flags |= IORESOURCE_IO | IORESOURCE_SIZEALIGN;
-     if (realloc_head)
-             add_to_list(realloc_head, bridge, b_res, pci_cardbus_io_size, 0 /* dont care */);
+     b_res[0].start = pci_cardbus_io_size;
+     b_res[0].end = b_res[0].start + pci_cardbus_io_size - 1;
+     b_res[0].flags |= IORESOURCE_IO | IORESOURCE_STARTALIGN;
+     if (realloc_head) {
+             b_res[0].end -= pci_cardbus_io_size;
+             add_to_list(realloc_head, bridge, b_res, pci_cardbus_io_size,
+                             pci_cardbus_io_size);
+     }
 
-     b_res[1].start = 0;
-     b_res[1].flags |= IORESOURCE_IO | IORESOURCE_SIZEALIGN;
-     if (realloc_head)
-             add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size, 0 /* dont care */);
+     b_res[1].start = pci_cardbus_io_size;
+     b_res[1].end = b_res[1].start + pci_cardbus_io_size - 1;
+     b_res[1].flags |= IORESOURCE_IO | IORESOURCE_STARTALIGN;
+     if (realloc_head) {
+             b_res[1].end -= pci_cardbus_io_size;
+             add_to_list(realloc_head, bridge, b_res+1, pci_cardbus_io_size,
+                              pci_cardbus_io_size);
+     }
 
       /* MEM1 must not be pref mmio */
       pci_read_config_word(bridge, PCI_CB_BRIDGE_CONTROL, &ctrl);

@@ -939,28 +948,28 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,
        * twice the size.
        */
       if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM0) {
-             b_res[2].start = 0;
-             b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH | IORESOURCE_SIZEALIGN;
-             if (realloc_head)
-                     add_to_list(realloc_head, bridge, b_res+2, pci_cardbus_mem_size, 0 /* dont care */);
+             b_res[2].start = pci_cardbus_mem_size;
+             b_res[2].end = b_res[2].start + pci_cardbus_mem_size - 1;
+             b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH |
+                               IORESOURCE_STARTALIGN;

drivers/pci/setup-bus.c static void pci_bus_size_cardbus(struct pci_bus *bus, · line 950

Quoted 10 lines

drivers/pci/setup-bus.c +5 -4

+             if (realloc_head) {
+                     b_res[2].end -= pci_cardbus_mem_size;
+                     add_to_list(realloc_head, bridge, b_res+2,
+                              pci_cardbus_mem_size, pci_cardbus_mem_size);
+             }
 
-             b_res[3].start = 0;
-             b_res[3].flags |= IORESOURCE_MEM | IORESOURCE_SIZEALIGN;
-             if (realloc_head)
-                     add_to_list(realloc_head, bridge, b_res+3, pci_cardbus_mem_size, 0 /* dont care */);

The b_res_3_size has to be reduced to half here. Otherwise it will try allocate 2*pci_cardbus_mem_size to the BAR3..

               b_res_3_size = pci_cardbus_mem_size;

drivers/pci/setup-bus.c static void pci_bus_size_cardbus(struct pci_bus *bus, · line 962

Quoted 7 lines

drivers/pci/setup-bus.c +2 -5

-     } else {
-             b_res[3].start = 0;
-             b_res[3].flags |= IORESOURCE_MEM | IORESOURCE_SIZEALIGN;
-             if (realloc_head)
-                     add_to_list(realloc_head, bridge, b_res+3, pci_cardbus_mem_size * 2, 0 /* dont care */);
+             /* reduce that to half */
+             b_res_3_size = pci_cardbus_mem_size;

b_res3_3_size should not be updated here, since BAR3 has to be allocated 2*pci_cardbus_mem_size resource.

Quoted 23 lines · Ram Pai

Quoted 22 lines · Yinghai Lu

We should not set the requested size to -2.

that will confuse the resource list sorting with align when SIZEALIGN is used.

Change to STARTALIGN and pass align from start.

We are safe to do that just as we do that regular pci bridge.

In the long run, we should just treat cardbus like regular pci bridge.

Also fix when realloc is not passed, should keep the requested size.

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |   63 ++++++++++++++++++++++++++--------------------

 1 files changed, 36 insertions(+), 27 deletions(-)

drivers/pci/setup-bus.c +0 -0

index d5897c3..3b3932a 100644
@@ -898,21 +898,30 @@ static void pci_bus_size_cardbus(struct pci_bus *bus,

Quoted 18 lines

Quoted 3 lines

-             b_res[3].flags |= IORESOURCE_MEM | IORESOURCE_SIZEALIGN;
-             if (realloc_head)
-                     add_to_list(realloc_head, bridge, b_res+3, pci_cardbus_mem_size, 0 /* dont care */);

The b_res_3_size has to be reduced to half here. Otherwise it will try allocate 2*pci_cardbus_mem_size to the BAR3..

               b_res_3_size = pci_cardbus_mem_size;

Quoted 7 lines

-     } else {
-             b_res[3].start = 0;
-             b_res[3].flags |= IORESOURCE_MEM | IORESOURCE_SIZEALIGN;
-             if (realloc_head)
-                     add_to_list(realloc_head, bridge, b_res+3, pci_cardbus_mem_size * 2, 0 /* dont care */);
+             /* reduce that to half */
+             b_res_3_size = pci_cardbus_mem_size;

Quoted 3 lines

b_res3_3_size should not be updated here, since BAR3 has to be allocated 2*pci_cardbus_mem_size resource.

looks like you did not read the patch correctly

that else {} get removed already in this patch

please check segment after patch...

	/*

	 * If we have prefetchable memory support, allocate
	 * two regions.  Otherwise, allocate one region of
	 * twice the size.
	 */
	if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM0) {
		b_res[2].start = pci_cardbus_mem_size;
		b_res[2].end = b_res[2].start + pci_cardbus_mem_size - 1;
		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH |
				  IORESOURCE_STARTALIGN;
		if (realloc_head) {

			b_res[2].end -= pci_cardbus_mem_size;
			add_to_list(realloc_head, bridge, b_res+2,
				 pci_cardbus_mem_size, pci_cardbus_mem_size);
		}

		/* reduce that to half */
		b_res_3_size = pci_cardbus_mem_size;
	}

..snip..

Quoted 15 lines

       * If we have prefetchable memory support, allocate
       * two regions.  Otherwise, allocate one region of
       * twice the size.
       */
      if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM0) { b_res[2].start = pci_cardbus_mem_size; b_res[2].end = b_res[2].start + pci_cardbus_mem_size - 1; b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH | IORESOURCE_STARTALIGN;
              if (realloc_head) {
                      b_res[2].end -= pci_cardbus_mem_size; add_to_list(realloc_head, bridge, b_res+2, pci_cardbus_mem_size, pci_cardbus_mem_size); }

Quoted 3 lines

              /* reduce that to half */ b_res_3_size = pci_cardbus_mem_size; }

ACK. Ok. got it. This looks correct.

Quoted 21 lines · Ram Pai

..snip..

Quoted 18 lines

       * If we have prefetchable memory support, allocate
       * two regions.  Otherwise, allocate one region of
       * twice the size.
       */
      if (ctrl & PCI_CB_BRIDGE_CTL_PREFETCH_MEM0) { b_res[2].start = pci_cardbus_mem_size; b_res[2].end = b_res[2].start + pci_cardbus_mem_size - 1; b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH | IORESOURCE_STARTALIGN;
              if (realloc_head) {
                      b_res[2].end -= pci_cardbus_mem_size; add_to_list(realloc_head, bridge, b_res+2, pci_cardbus_mem_size, pci_cardbus_mem_size); }

              /* reduce that to half */ b_res_3_size = pci_cardbus_mem_size; }

Quoted 1 line

ACK. Ok. got it. This looks correct.

Good, So we have

Acked-by Ram Pai <[email protected]>

Tested-by Dominik Brodowski <[email protected]>

Hope Jesse will not miss to add them

Quoted 4 lines

Quoted 1 line

ACK. Ok. got it. This looks correct.

Good, So we have

Quoted 4 lines

Acked-by Ram Pai <[email protected]>

Tested-by Dominik Brodowski <[email protected]>

Hope Jesse will not miss to add them

Yeah looks fine.  I'd like to see an ack from Dominik on 5/9 as well though.  Can you include the acks and tested-bys when you re-post 3-9 with bug references and any other comments included?

Let the user could enable and disable with pci=realloc=on or pci=realloc=off

Also
1. move variable and functions near the place they are used.
2. change macro to function
3. change related functions and variable to static and _init
4. update parameter description accordingly.

-v2: still honor pci=realloc, and treat it as pci=realloc=on
also use enum instead of ...

Signed-off-by Yinghai Lu <[email protected]>

---
 Documentation/kernel-parameters.txt |    8 ++++++--
 drivers/pci/pci.c                   |    4 +++-
 drivers/pci/pci.h                   |    2 +-
 drivers/pci/setup-bus.c             |   33 ++++++++++++++++++++++++++-------
 4 files changed, 36 insertions(+), 11 deletions(-)

Documentation/kernel-parameters.txt +0 -0

index 033d4e6..e11e5dd 100644
@@ -2109,8 +2109,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				the default.

let user know they could try if pci=realloc could help.

Suggested-by Jesse Barnes <[email protected]>

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +0 -0

index 22454c5..9526038 100644

If bios does not assign those BAR or wrong address, then kernel will try to do pci realloc.

in that case, user still can use pci=realloc=off to override it.

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |   28 ++++++++++++++++++++++++++++
 1 files changed, 28 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +26 -0

index 9526038..520f256 100644
@@ -1293,6 +1293,31 @@ static bool __init pci_realloc_enabled(void)
 	return pci_realloc_enable >= enable_yes_user;
 }
 
+static void __init pci_realloc_detect(void)
+{
+	struct pci_dev *dev = NULL;
+
+	if (pci_realloc_enable != enable_not_set)
+		return;
+
+#ifdef CONFIG_PCI_IOV
+	for_each_pci_dev(dev) {
+		int i;
+
+		for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
+			struct resource *r = &dev->resource[i];
+
+			/* Not assigned, or rejected by kernel */
+			if (r->flags && !r->start) {
+				pci_realloc_enable = enable_yes_detected;
+
+				return;
+			}
+		}
+	}
+#endif
+}
+
 /*
  * first try will not touch pci bridge res
  * second  and later try will clear small leaf bridge res

@@ -1314,6 +1339,7 @@ pci_assign_unassigned_resources(void)
 	int pci_try_num = 1;
 
 	/* don't realloc if asked to do so */
+	pci_realloc_detect();
 	if (pci_realloc_enabled()) {
 		int max_depth = pci_get_max_depth();
 

Quoted 55 lines · On Sat,  4 Feb 2012 22:55:08 -0800 Yinghai Lu <[email protected]> wrote:

If bios does not assign those BAR or wrong address, then kernel will try to do pci realloc.

in that case, user still can use pci=realloc=off to override it.

Signed-off-by Yinghai Lu <[email protected]>

---
 drivers/pci/setup-bus.c |   28 ++++++++++++++++++++++++++++

 1 files changed, 28 insertions(+), 0 deletions(-)

drivers/pci/setup-bus.c +26 -0

index 9526038..520f256 100644
@@ -1293,6 +1293,31 @@ static bool __init pci_realloc_enabled(void)
       return pci_realloc_enable >= enable_yes_user;
  }
 
+static void __init pci_realloc_detect(void)
+{
+     struct pci_dev *dev = NULL;
+
+     if (pci_realloc_enable != enable_not_set)
+             return;
+
+#ifdef CONFIG_PCI_IOV
+     for_each_pci_dev(dev) {
+             int i;
+
+             for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++) {
+                     struct resource *r = &dev->resource[i];
+
+                     /* Not assigned, or rejected by kernel */
+                     if (r->flags && !r->start) {
+                             pci_realloc_enable = enable_yes_detected;
+
+                             return;
+                     }
+             }
+     }
+#endif
+}
+
  /*
   * first try will not touch pci bridge res
   * second  and later try will clear small leaf bridge res

@@ -1314,6 +1339,7 @@ pci_assign_unassigned_resources(void)
       int pci_try_num = 1;
 
       /* don't realloc if asked to do so */
+     pci_realloc_detect();
       if (pci_realloc_enabled()) {
               int max_depth = pci_get_max_depth();
 

drivers/pci/setup-bus.c again: · line 1381

Quoted 8 lines

drivers/pci/setup-bus.c +2 -0

@@ -1348,6 +1374,8 @@ again:
       if (tried_times >= pci_try_num) {
               if (pci_realloc_enable == enable_not_set)
                       printk(KERN_INFO "Some pci devices resources are not assigned, please try to boot with pci=realloc\n");
+             else if (pci_realloc_enable == enable_yes_detected)
+                     printk(KERN_INFO "Automatically enabled pci realloc, if you have problem, please try to boot with pci=realloc=off\n");
 
               free_list(&fail_head);
               goto enable_and_dump;

Not sure I like this one either.  Distros will want to enable IOV by default, but in most configs users still won't use it, and many BIOSes won't bother to allocate IOV space.  So defaulting to trying to do so will likely cause a lot of unnecessary re-allocation.

So distro guidance would be appreciated here for the default behavior.