Re: [PATCH 2/2] ACPI / PCI: Account for ARI in _PRT lookups
From: Don Dutile
Date: Tue May 26 2015 - 16:58:59 EST
On 05/26/2015 04:42 PM, Alex Williamson wrote:
On Tue, 2015-05-26 at 16:06 -0400, Don Dutile wrote:
On 05/26/2015 01:54 PM, Alex Williamson wrote:
The PCIe specification, rev 3.0, section 2.2.8.1, contains the
following implementation note:
Virtual Wire Mapping for INTx Interrupts From ARI Devices
The implied Device Number for an ARI Device is 0. When ARI-aware
software (including BIOS and operating system) enables ARI
Forwarding in the Downstream Port immediately above an ARI Device
in order to access its Extended Functions, software must
comprehend that the Downstream Port will use Device Number 0 for
the virtual wire mappings of INTx interrupts coming from all
Functions of the ARI Device. If non-ARI-aware software attempts
to determine the virtual wire mappings for Extended Functions, it
can come up with incorrect mappings by examining the traditional
Device Number field and finding it to be non-0.
We account for this in pci_swizzle_interrupt_pin(), but it looks like
we miss it here, looking for a _PRT entry with a slot matching the
ARI device slot number. This can cause errors like:
pcieport 0000:80:03.0: can't derive routing for PCI INT B
sfc 0000:82:01.1: PCI INT B: no GSI
pci_dev.irq is then invalid, resulting in errors for drivers that
attempt to enable INTx on the device. Fix by using slot 0 for ARI
enabled devices.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
drivers/acpi/pci_irq.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
index b1def41..65e83cd 100644
--- a/drivers/acpi/pci_irq.c
+++ b/drivers/acpi/pci_irq.c
@@ -163,7 +163,7 @@ static int acpi_pci_irq_check_entry(acpi_handle handle, struct pci_dev *dev,
{
int segment = pci_domain_nr(dev->bus);
int bus = dev->bus->number;
- int device = PCI_SLOT(dev->devfn);
+ int device = pci_ari_enabled(dev->bus) ? 0 : PCI_SLOT(dev->devfn);
struct acpi_prt_entry *entry;
if (((prt->address >> 16) & 0xffff) != device ||
@@ -181,7 +181,7 @@ static int acpi_pci_irq_check_entry(acpi_handle handle, struct pci_dev *dev,
*/
entry->id.segment = segment;
entry->id.bus = bus;
- entry->id.device = (prt->address >> 16) & 0xFFFF;
+ entry->id.device = PCI_SLOT(dev->devfn);
I would expect that this should be = device, not PCI_SLOT(dev->devfn),
esp if used by ACPI core, since it'll be expecting a swizzle from device 0,
per above spec.
But it's not used by ACPI core.
Additionally, if you look at the beginning of this function, this check is performed:
if (((prt->address >> 16) & 0xffff) != device ||
prt->pin + 1 != pin)
return -ENODEV;
So, that implies you leave this assignment as is,
or set it to device -- six of one, half-dozen another.
TBH, I didn't really know what to do with this field. struct
acpi_prt_entry is defined locally to this file, so we're not passing it
out to ACPI core for anything. The only consumer of entry.id in this
call path is the debug print at the bottom of the function:
Well, do_prt_fixups(entry, prt) is called right after the setting,
and although your patch leaves the state of id.device as it was before
to enable the matches in the current list, that may not be so later.
I'd leave the id.device as it was -- set to prt->address >> 16) & 0xFFFF
for the proper matching all around.
if you want the printf to change, patch it to use PCI_SLOT(dev->devfn) instead of entry->id.device.
ACPI_DEBUG_PRINT_RAW((ACPI_DB_INFO,
" %04x:%02x:%02x[%c] -> %s[%d]\n",
entry->id.segment, entry->id.bus,
entry->id.device, pin_name(entry->pin),
prt->source, entry->index));
Which is the reason I chose to use the value that I did, because using
'device', aka 0, in the ARI path would be confusing.
I think that the only reason entry.id exists is for the fixup code in
this file. I'm happy to leave it as 'device' or the original
'(prt->address >> 16) & 0xFFFF', but what I have feels more correct for
the debug printk if nothing else. Thanks,
Alex
entry->pin = prt->pin + 1;
do_prt_fixups(entry, prt);
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