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From: H. Peter Anvin on 14 Jul 2010 15:00
So I suggest the following changes...

On 07/13/2010 07:19 PM, Jesse Barnes wrote:
>>
>> static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
>> {
>> int pos;
>> u32 pcie_cap = 0, cap_data;
>> printk("fixed_bar_cap, bus: %p devfn: %u\n", bus, devfn);
>> pos = PCIE_CAP_OFFSET;
>> while (pos) {

while (pos >= PCIE_CAP_OFFSET) {

>> printk("Before read..\n");
>> if (raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
>> devfn, pos, 4, &pcie_cap))
>> return 0;
>> printk("pcie_cap: %u", pcie_cap);
>>
- if (pcie_cap == 0xffffffff)
- return 0;

+ if (PCI_EXT_CAP_ID(pcie_cap) == 0x0000 ||
+ PCI_EXT_CAP_ID(pcie_cap) == 0xffff)
+ break;

>> printk("Checking vendor..\n");

>> if (PCI_EXT_CAP_ID(pcie_cap) == PCI_EXT_CAP_ID_VNDR) {
>> printk("reading domain_nr\n");
>> raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
>> devfn, pos + 4, 4, &cap_data);
>> printk("cap_data: %u\n", cap_data);
>> if ((cap_data & 0xffff) == PCIE_VNDR_CAP_ID_FIXED_BAR)
>> return pos;
>> }
>>
>> pos = pcie_cap >> 20;

pos = (pcie_cap >> 20) & 0xffc;

>> printk("pos after shift: %i\n", pos);
>> }
>>
>> printk("Returning from fixed_bar_cap\n");
>> return 0;
>> }
>>
>>
>
> I thought a related bug was fixed already; the code should be returning
> all zeros for non-existent BAR reads.
>

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From: H. Peter Anvin on 14 Jul 2010 15:10
On 07/14/2010 11:59 AM, Jesse Barnes wrote:
>
> Changes look ok to me, though I'd prefer not hitting this code at all
> on non-Moorestown if at all possible.
>

I guess that's okay in the short term, but I'm guessing fixed BARs in
some form is eventually going to make it into the general PCI spec.

-hpa

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From: Ben Greear on 14 Jul 2010 15:30
On 07/14/2010 11:52 AM, H. Peter Anvin wrote:
> So I suggest the following changes...
>
> On 07/13/2010 07:19 PM, Jesse Barnes wrote:
>>>
>>> static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
>>> {
>>> int pos;
>>> u32 pcie_cap = 0, cap_data;
>>> printk("fixed_bar_cap, bus: %p devfn: %u\n", bus, devfn);
>>> pos = PCIE_CAP_OFFSET;
>>> while (pos) {
>
> while (pos>= PCIE_CAP_OFFSET) {
>
>>> printk("Before read..\n");
>>> if (raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
>>> devfn, pos, 4,&pcie_cap))
>>> return 0;
>>> printk("pcie_cap: %u", pcie_cap);
>>>
> - if (pcie_cap == 0xffffffff)
> - return 0;
>
> + if (PCI_EXT_CAP_ID(pcie_cap) == 0x0000 ||
> + PCI_EXT_CAP_ID(pcie_cap) == 0xffff)
> + break;

This seems to work for me. I'm using this patch against
2.6.34.y:

diff --git a/arch/x86/pci/mrst.c b/arch/x86/pci/mrst.c
index 1cdc02c..ee93fd0 100644
--- a/arch/x86/pci/mrst.c
+++ b/arch/x86/pci/mrst.c
@@ -61,13 +61,14 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
if (!raw_pci_ext_ops)
return 0;

- while (pos) {
+ while (pos >= PCIE_CAP_OFFSET) {
if (raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
devfn, pos, 4, &pcie_cap))
return 0;

- if (pcie_cap == 0xffffffff)
- return 0;
+ if (PCI_EXT_CAP_ID(pcie_cap) == 0x0000 ||
+ PCI_EXT_CAP_ID(pcie_cap) == 0xffff)
+ break;

if (PCI_EXT_CAP_ID(pcie_cap) == PCI_EXT_CAP_ID_VNDR) {
raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
@@ -76,7 +77,7 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
return pos;
}

- pos = pcie_cap >> 20;
+ pos = (pcie_cap >> 20) & 0xffc;
}

return 0;


Thanks,
Ben


>
>>> printk("Checking vendor..\n");
>
>>> if (PCI_EXT_CAP_ID(pcie_cap) == PCI_EXT_CAP_ID_VNDR) {
>>> printk("reading domain_nr\n");
>>> raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
>>> devfn, pos + 4, 4,&cap_data);
>>> printk("cap_data: %u\n", cap_data);
>>> if ((cap_data& 0xffff) == PCIE_VNDR_CAP_ID_FIXED_BAR)
>>> return pos;
>>> }
>>>
>>> pos = pcie_cap>> 20;
>
> pos = (pcie_cap>> 20)& 0xffc;
>
>>> printk("pos after shift: %i\n", pos);
>>> }
>>>
>>> printk("Returning from fixed_bar_cap\n");
>>> return 0;
>>> }
>>>
>>>
>>
>> I thought a related bug was fixed already; the code should be returning
>> all zeros for non-existent BAR reads.
>>
>
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> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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--
Ben Greear <greearb(a)candelatech.com>
Candela Technologies Inc http://www.candelatech.com

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From: H. Peter Anvin on 14 Jul 2010 16:00
On 07/14/2010 12:01 PM, Pan, Jacob jun wrote:
>
> Can we use PCI_EXT_CAP_NEXT to replace this line?
> pos = (pcie_cap >> 20) & 0xffc
>

Presumably, I haven't checked the definition of that macro, but that
would be the logical semantics.

-hpa

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From: Ben Greear on 15 Jul 2010 12:40
On 07/14/2010 12:55 PM, H. Peter Anvin wrote:
> On 07/14/2010 12:01 PM, Pan, Jacob jun wrote:
>>
>> Can we use PCI_EXT_CAP_NEXT to replace this line?
>> pos = (pcie_cap>> 20)& 0xffc
>>
>
> Presumably, I haven't checked the definition of that macro, but that
> would be the logical semantics.
>
> -hpa

Are one of you guys going to submit a fix upstream (and hopefully
to stable)? Since you guys actually understand the code, probably
best that you do it....

Thanks,
Ben

--
Ben Greear <greearb(a)candelatech.com>
Candela Technologies Inc http://www.candelatech.com

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