[vfio-users] [FEEDBACK NEEDED] Additionnal tips to include in the Arch wiki article

[Colin Godsey]

So I checked back on my old config- forcing X2APIC helped me on 3.x kernels
only, I have not observed any effect on 4.x kernels though, so this can
most-likely be disregarded for Arch.

On Tue, May 24, 2016 at 11:45 AM Spam House <kthxplzdie at gmail.com> wrote:

> Hey Colin,
>
> I am curious about this as well. Please provide more information on your
> setup regarding X2APIC.
>
> On Sat, May 21, 2016 at 10:42 AM, Colin Godsey <crgodsey at gmail.com> wrote:
>
>> Windows 10 forcing X2APIC: https://support.microsoft.com/en-us/kb/2303458
>>
>> This helped a bunch for me at least on 4.4- I think there was some
>> confusion on the correct way to signal the guest on what APIC to use,
>> forcing this gave me much better %sys times. AFAIK it can also still be
>> used with hyper-v APIC because that’s just the EOI para-virtualization.
>>
>> On Fri, May 20, 2016 at 2:28 PM Alex Williamson <
>> alex.l.williamson at gmail.com> wrote:
>>
>>> On Fri, May 20, 2016 at 11:38 AM, Nicolas Roy-Renaud <
>>> nicolas.roy-renaud.1 at ens.etsmtl.ca> wrote:
>>>
>>>> Did you have any issues with efifb or some other driver grabbing the
>>>> gard before vfio-pci? What are your IOMMU groups like, which chard is your
>>>> boot_vga, what script or method do you use to get vfio-pci to bind with
>>>> your card, what's your kernel command line and what modules are included in
>>>> your initramfs?
>>>>
>>>> I've struggled with getting my primary GPU to work correctly for a
>>>> passthrough like this, and I ended up switching it up with the secondary
>>>> because I simply couldn't get it to work properly (I'd keep getting
>>>> something about "Invalid ROM contents") and I couldn't see my boot
>>>> logs until the host driver finished loading. It's really inconvenient now
>>>> becuase my motherboard is designed so that having a full-size GPU in the
>>>> second PCIe slot blocks 4 SATA ports out of 6, so I need to have L-shaped
>>>> cables in a bunch of places to make everything work properly.
>>>>
>>>
>>> The boot VGA ROM is handled differently from other PCI ROMs in Linux,
>>> when you read it you're actually reading a shadow copy of it placed at
>>> 0xc0000, which has its roots back in the original IBM PC history.
>>> Execution of the VGA ROM is allowed to modify this copy of the ROM image in
>>> memory.  Thus you're really not getting a pristine copy of the device ROM
>>> and it can often lead to these invalid ROM contents messages.  I wish we
>>> provided raw access to the PCI option ROM in these cases as well.  For now,
>>> if you do have these sorts of invalid ROM messages, I would suggest that
>>> you at least boot with the card as secondary, dump the ROM, then use that
>>> collected image with the romfile= option rather than use the shadow copy.
>>> I had to add some code to vfio to fix device IDs and checksums for IGD
>>> assignment because of this, I don't know if there's any standard fixup we
>>> can do for other vendors.  Thanks,
>>>
>>> Alex
>>> _______________________________________________
>>> vfio-users mailing list
>>> vfio-users at redhat.com
>>> https://www.redhat.com/mailman/listinfo/vfio-users
>>>
>>
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>
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