1 files changed, 43 insertions, 16 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7eb6eb384e36..c140cb29ee7e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4959,11 +4959,13 @@ static DEFINE_SPINLOCK(resource_alignment_lock);
 /**
  * pci_specified_resource_alignment - get resource alignment specified by user.
  * @dev: the PCI device to get
+ * @resize: whether or not to change resources' size when reassigning alignment
  *
  * RETURNS: Resource alignment if it is specified.
  *          Zero if it is not specified.
  */
-static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
+static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
+                                                        bool *resize)
 {
         int seg, bus, slot, func, align_order, count;
         unsigned short vendor, device, subsystem_vendor, subsystem_device;
@@ -5005,6 +5007,7 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
                                 (!device || (device == dev->device)) &&
                                 (!subsystem_vendor || (subsystem_vendor == dev->subsystem_vendor)) &&
                                 (!subsystem_device || (subsystem_device == dev->subsystem_device))) {
+                                *resize = true;
                                 if (align_order == -1)
                                         align = PAGE_SIZE;
                                 else
@@ -5030,6 +5033,7 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
                                 bus == dev->bus->number &&
                                 slot == PCI_SLOT(dev->devfn) &&
                                 func == PCI_FUNC(dev->devfn)) {
+                                *resize = true;
                                 if (align_order == -1)
                                         align = PAGE_SIZE;
                                 else
@@ -5050,7 +5054,7 @@ out:
 }
 
 static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
-                                           resource_size_t align)
+                                           resource_size_t align, bool resize)
 {
         struct resource *r = &dev->resource[bar];
         resource_size_t size;
@@ -5069,23 +5073,45 @@ static void pci_request_resource_alignment(struct pci_dev *dev, int bar,
                 return;
 
         /*
-         * Increase the size of the resource.  BARs are aligned on their
-         * size, so when we reallocate space for this resource, we'll
-         * allocate it with the larger alignment.  It also prevents
-         * assignment of any other BARs inside the size.  If we're
-         * requesting page alignment, this means no other BARs will share
-         * the page.
+         * Increase the alignment of the resource.  There are two ways we
+         * can do this:
          *
-         * This makes the resource larger than the hardware BAR, which may
-         * break drivers that compute things based on the resource size,
-         * e.g., to find registers at a fixed offset before the end of the
-         * BAR.  We hope users don't request alignment for such devices.
+         * 1) Increase the size of the resource.  BARs are aligned on their
+         *    size, so when we reallocate space for this resource, we'll
+         *    allocate it with the larger alignment.  This also prevents
+         *    assignment of any other BARs inside the alignment region, so
+         *    if we're requesting page alignment, this means no other BARs
+         *    will share the page.
+         *
+         *    The disadvantage is that this makes the resource larger than
+         *    the hardware BAR, which may break drivers that compute things
+         *    based on the resource size, e.g., to find registers at a
+         *    fixed offset before the end of the BAR.
+         *
+         * 2) Retain the resource size, but use IORESOURCE_STARTALIGN and
+         *    set r->start to the desired alignment.  By itself this
+         *    doesn't prevent other BARs being put inside the alignment
+         *    region, but if we realign *every* resource of every device in
+         *    the system, none of them will share an alignment region.
+         *
+         * When the user has requested alignment for only some devices via
+         * the "pci=resource_alignment" argument, "resize" is true and we
+         * use the first method.  Otherwise we assume we're aligning all
+         * devices and we use the second.
          */
+
         dev_info(&dev->dev, "BAR%d %pR: requesting alignment to %#llx\n",
                  bar, r, (unsigned long long)align);
 
-        r->start = 0;
-        r->end = align - 1;
+        if (resize) {
+                r->start = 0;
+                r->end = align - 1;
+        } else {
+                r->flags &= ~IORESOURCE_SIZEALIGN;
+                r->flags |= IORESOURCE_STARTALIGN;
+                r->start = align;
+                r->end = r->start + size - 1;
+        }
         r->flags |= IORESOURCE_UNSET;
 }
 
@@ -5102,6 +5128,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
         struct resource *r;
         resource_size_t align;
         u16 command;
+        bool resize = false;
 
         /*
          * VF BARs are read-only zero according to SR-IOV spec r1.1, sec
@@ -5113,7 +5140,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
                 return;
 
         /* check if specified PCI is target device to reassign */
-        align = pci_specified_resource_alignment(dev);
+        align = pci_specified_resource_alignment(dev, &resize);
         if (!align)
                 return;
 
@@ -5131,7 +5158,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
         pci_write_config_word(dev, PCI_COMMAND, command);
 
         for (i = 0; i <= PCI_ROM_RESOURCE; i++)
-                pci_request_resource_alignment(dev, i, align);
+                pci_request_resource_alignment(dev, i, align, resize);
 
         /*
          * Need to disable bridge's resource window,