xen-pciback: return proper values during BAR sizing

Reads following writes with all address bits set to 1 should return all
changeable address bits as one, not the BAR size (nor, as was the case
for the upper half of 64-bit BARs, the high half of the region's end
address). Presumably this didn't cause any problems so far because
consumers use the value to calculate the size (usually via val & -val),
and do nothing else with it.

But also consider the exception here: Unimplemented BARs should always
return all zeroes.

And finally, the check for whether to return the sizing address on read
for the ROM BAR should ignore all non-address bits, not just the ROM
Enable one.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
index ad3d17d29c81..9ead1c2ff1dd 100644
--- a/drivers/xen/xen-pciback/conf_space_header.c
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -145,7 +145,7 @@ static int rom_write(struct pci_dev *dev, int offset, u32 value, void *data)
         /* A write to obtain the length must happen as a 32-bit write.
          * This does not (yet) support writing individual bytes
          */
-        if (value == ~PCI_ROM_ADDRESS_ENABLE)
+        if ((value | ~PCI_ROM_ADDRESS_MASK) == ~0U)
                 bar->which = 1;
         else {
                 u32 tmpval;
@@ -225,38 +225,42 @@ static inline void read_dev_bar(struct pci_dev *dev,
                            (PCI_BASE_ADDRESS_SPACE_MEMORY |
                                 PCI_BASE_ADDRESS_MEM_TYPE_64))) {
                         bar_info->val = res[pos - 1].start >> 32;
-                        bar_info->len_val = res[pos - 1].end >> 32;
+                        bar_info->len_val = -resource_size(&res[pos - 1]) >> 32;
                         return;
                 }
         }
 
+        if (!res[pos].flags ||
+            (res[pos].flags & (IORESOURCE_DISABLED | IORESOURCE_UNSET |
+                               IORESOURCE_BUSY)))
+                return;
+
         bar_info->val = res[pos].start |
                         (res[pos].flags & PCI_REGION_FLAG_MASK);
-        bar_info->len_val = resource_size(&res[pos]);
+        bar_info->len_val = -resource_size(&res[pos]) |
+                            (res[pos].flags & PCI_REGION_FLAG_MASK);
 }
 
 static void *bar_init(struct pci_dev *dev, int offset)
 {
-        struct pci_bar_info *bar = kmalloc(sizeof(*bar), GFP_KERNEL);
+        struct pci_bar_info *bar = kzalloc(sizeof(*bar), GFP_KERNEL);
 
         if (!bar)
                 return ERR_PTR(-ENOMEM);
 
         read_dev_bar(dev, bar, offset, ~0);
-        bar->which = 0;
 
         return bar;
 }
 
 static void *rom_init(struct pci_dev *dev, int offset)
 {
-        struct pci_bar_info *bar = kmalloc(sizeof(*bar), GFP_KERNEL);
+        struct pci_bar_info *bar = kzalloc(sizeof(*bar), GFP_KERNEL);
 
         if (!bar)
                 return ERR_PTR(-ENOMEM);
 
         read_dev_bar(dev, bar, offset, ~PCI_ROM_ADDRESS_ENABLE);
-        bar->which = 0;
 
         return bar;
 }