Re: [Qemu-devel] [PATCH v3] pci : Add pba_offset PCI quirk for Chelsio T5 devices

[Gabriel Laupre]

> What you are suggesting is:
> If table_offset is not as expected, then check if it's a chelsio device.
> If it's not, then print a message. On the other hand, if it's a chelsio 
> device, then let msix_init() catch the error. Why ? And if we are sure that 
> msix_init will error out, what's the purpose of the table_offset check ?

The first test of table_offset is indeed useless for the quirk as we know that 
the hardware problem comes from the pba_offset. We shouldn't mix the different 
potential errors in the same test, I agree.


-----Original Message-----
From: Bandan Das [mailto:address@hidden 
Sent: Tuesday, June 30, 2015 6:48 PM
To: Gabriel Laupre
Cc: address@hidden; Casey Leedom; address@hidden; address@hidden; Anish Bhatt; 
Michael Boksanyi; address@hidden; address@hidden
Subject: Re: [Qemu-devel] [PATCH v3] pci : Add pba_offset PCI quirk for Chelsio 
T5 devices

Gabriel Laupre <address@hidden> writes:

> @ Bandan ...
>> > + + /* Chelsio T5 Virtual Function devices are encoded as 0x58xx
>> > for T5 + * adapters. The T5 hardware returns an incorrect value of
>> > 0x8000 for + * the VF PBA offset. The correct value is 0x1000, so 
>> > we hard code that + * here. */ + if (vendor == 
>> > PCI_VENDOR_ID_CHELSIO && (device & 0xff00) == 0x5800) { +
>> > vdev->msix->pba_offset = 0x1000;
>
>> For the rare case where table_offset is wrong for the device being
> checked for above and pba_offset is actually correct, shouldn't we 
> fail ?
>
> I don't know if it is relevant to do all the tests here because in the 
> function msix_init() all size are checked. I would prefer keeping this 
> test as this to simplify the quirk, i.e. just testing the device 
> first, and if another size than the pba_offset is wrong, then the 
> sanity check in the function msix_init() will catch the error.

Ok, here's the excerpt:

+    /* Test the size of the pba variables and catch if they extend outside of
+     * the specified BAR. If it is the case, we have a broken configuration or
+     * we need to apply a hardware specific quirk. */
+    if (vdev->msix->table_offset >=
+        vdev->bars[vdev->msix->table_bar].region.size ||
+        vdev->msix->pba_offset >=
+        vdev->bars[vdev->msix->pba_bar].region.size) {
+
+        PCIDevice *pdev = &vdev->pdev;
+        uint16_t vendor = pci_get_word(pdev->config + PCI_VENDOR_ID);
+        uint16_t device = pci_get_word(pdev->config + PCI_DEVICE_ID);
+
+        /* Chelsio T5 Virtual Function devices are encoded as 0x58xx for T5
+         * adapters. The T5 hardware returns an incorrect value of 0x8000 for
+         * the VF PBA offset. The correct value is 0x1000, so we hard code that
+         * here. */
+        if (vendor == PCI_VENDOR_ID_CHELSIO && (device & 0xff00) == 0x5800) {
+            vdev->msix->pba_offset = 0x1000;
+        } else {
+            error_report("vfio: Hardware reports invalid configuration, "
+            "MSIX data outside of specified BAR");
+            return -EINVAL;
+        }
+    }


What you are suggesting is:
If table_offset is not as expected, then check if it's a chelsio device.
If it's not, then print a message. On the other hand, if it's a chelsio device, 
then let msix_init() catch the error. Why ? And if we are sure that msix_init 
will error out, what's the purpose of the table_offset check ?

> @ Alex I corrected what you pointed out. I will send the patch v4 in a 
> minute.
>
> Thanks you
>
> Gabriel