[PATCH xserver 4/4] xfree86: promote one GPU screen if (NumScreens == 0 && NumGPUScreens > 0)

[Hans de Goede]

Hi,

On 05-09-16 14:39, Laszlo Ersek wrote:
> On 09/04/16 11:01, Hans de Goede wrote:

<snip>

> If a seasoned xserver developer is interested in fixing this problem,
> I'd like to file an upstream bug tracker entry for it, and assign it to
> him/her -- I'm way out of my depth here :)

I see that we've 2 redhat bugzillas for this, lets just track this
there. I've an idea how to fix this with a small and clean patch.
which will hopefully be acceptable despite Dave's preference for
a kernel fix (which I agree with, but is non trivial).

It looks like I'll be spending all my time on getting hw-cursor
support for prime into shape today, so I'll implement my idea
and do a fedora scratchbuild for you and Marcin to test
tomorrow. Any preference for a F24 or F25 build ?

Regards,

Hans



>
> Thanks
> Laszlo
>
>>
>>
>>  in these guests the X server currently exits with "No
>>> devices detected", unless the user provides a config file with a Device
>>> section that identifies the card by BusID.
>>>
>>> Although this behavior matches the documentation precisely, it is
>>> inconvenient for virtual machines, where the X server is expected to
>>> start
>>> regardless of the (unpredictable) PCI B/D/F of the "virtio-gpu-pci"
>>> device.
>>>
>>> Modify xf86BusConfig() so that if no screen has been found, but there is
>>> at least one GPU screen, one of the GPU screens be promoted to the single
>>> normal screen. (This change should be either unnoticeable on physical
>>> platforms, or beneficial even.) For this, call the
>>> xf86PromoteLastGPUScreenToLastScreen() helper function added in the last
>>> patch.
>>>
>>> Update the manual page accordingly. The documentation remains
>>> intentionally vague on what GPU screen gets promoted under the above
>>> circumstances. The statements about multi-head setups, and about
>>> single-head setups using the primary graphics card, are preserved intact.
>>>
>>> Cc: Adam Jackson <ajax at redhat.com>
>>> Cc: Dave Airlie <airlied at redhat.com>
>>> Cc: Keith Packard <keithp at keithp.com>
>>> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
>>> ---
>>>  hw/xfree86/common/xf86Bus.c  | 19 ++++++++++++++++---
>>>  hw/xfree86/man/xorg.conf.man | 21 ++++++++++++++++-----
>>>  2 files changed, 32 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/hw/xfree86/common/xf86Bus.c b/hw/xfree86/common/xf86Bus.c
>>> index dc83e2dde099..572d91fd223b 100644
>>> --- a/hw/xfree86/common/xf86Bus.c
>>> +++ b/hw/xfree86/common/xf86Bus.c
>>> @@ -127,10 +127,23 @@ xf86BusConfig(void)
>>>          xf86CallDriverProbe(xf86DriverList[i], FALSE);
>>>      }
>>>
>>> -    /* If nothing was detected, return now */
>>>      if (xf86NumScreens == 0) {
>>> -        xf86Msg(X_ERROR, "No devices detected.\n");
>>> -        return FALSE;
>>> +        if (xf86NumGPUScreens == 0) {
>>> +            /* If nothing was detected, return now */
>>> +            xf86Msg(X_ERROR, "No devices detected.\n");
>>> +            return FALSE;
>>> +        }
>>> +
>>> +        /*
>>> +         * If no screen was detected, but there is at least one GPU
>>> screen,
>>> +         * promote one of the latter to be the single screen. Note
>>> that a
>>> +         * graphics card matched by a Device.BusID (i.e., from the
>>> config file)
>>> +         * is added as a screen, not as a GPU screen; so if that
>>> happens, we
>>> +         * don't reach this code.
>>> +         */
>>> +        xf86PromoteLastGPUScreenToLastScreen();
>>> +        xf86Msg(X_WARNING, "Use Device.BusID to select a specific
>>> secondary "
>>> +                "graphics card.\n");
>>>      }
>>>
>>>      xf86VGAarbiterInit();
>>> diff --git a/hw/xfree86/man/xorg.conf.man b/hw/xfree86/man/xorg.conf.man
>>> index 94b199e6bac4..36f04febf2f4 100644
>>> --- a/hw/xfree86/man/xorg.conf.man
>>> +++ b/hw/xfree86/man/xorg.conf.man
>>> @@ -1353,11 +1353,22 @@ the
>>>  string has the form
>>>  .BI PCI: bus : device : function
>>>  (e.g., \(lqPCI:1:0:0\(rq might be appropriate for an AGP card).
>>> -This field is usually optional in single-head configurations when using
>>> -the primary graphics card.
>>> -In multi-head configurations, or when using a secondary graphics card
>>> in a
>>> -single-head configuration, this entry is mandatory.
>>> -Its main purpose is to make an unambiguous connection between the device
>>> +In multi-head configurations, this entry is mandatory.
>>> +It is usually optional in single-head configurations when using the
>>> primary
>>> +graphics card.
>>> +When using a secondary graphics card in a single-head configuration,
>>> +.B BusID
>>> +is recommended; if no graphics card can be identified as primary, nor
>>> is any
>>> +card selected by at least one
>>> +.B Device
>>> +section through the
>>> +.B BusID
>>> +field, then an unspecified secondary card (if any) is promoted to
>>> primary
>>> +status.
>>> +The main purpose of
>>> +.B BusID
>>> +is to make an unambiguous connection between the
>>> +.B Device
>>>  section and the hardware it is representing.
>>>  This information can usually be found by running the pciaccess tool
>>>  scanpci.
>>>
>