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

From: Jan Beulich
Date: Fri Jun 24 2016 - 05:13:45 EST


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;
}