[Xen-devel] [PATCH v3 1/2] xen-pciback: return proper values during BAR sizing

["Jan Beulich" <JBeulich@xxxxxxxx>]

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@xxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
v3: Use ~0U in rom_write(), to account for PCI_ROM_ADDRESS_MASK being
    of unsigned long type (relevant on 64-bit). (Note: Patch 2 is
    unchanged, and hence not being re-sent. I hope that, despite this
    being a bug fix from v2, retaining the R-b is okay.)
---
 drivers/xen/xen-pciback/conf_space_header.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

--- 4.7-rc4-xen-pciback-BAR.orig/drivers/xen/xen-pciback/conf_space_header.c
+++ 4.7-rc4-xen-pciback-BAR/drivers/xen/xen-pciback/conf_space_header.c
@@ -145,7 +145,7 @@ static int rom_write(struct pci_dev *dev
        /* 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 p
                           (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;
 }




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