Re: Regression: drm: Lobotomize set_busid nonsense for !pci drivers (a325725633c2)

[Hans de Goede <hdegoede@redhat.com>]

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Hi,

On 30-09-16 10:28, Hans de Goede wrote:
> Hi,
>

<snip>

> Xorg when running without a Xorg.conf searches for what it considers
> a "primary" gpu / video-card, basically it attempts to bring up the
> right card in setups where there are multiple cards and if it does not
> find one exits with an error.
>
> The xserver has a 2 step process for finding the primary card:
>
> 1) It searches for is a card which has a vga-bios mapped,
> as we've already determined in the mentioned Red Hat bug that works for
> the classic qemu emulated video-cards, but not for qemu's virtio-vga.
>
> 2) If that does not work Xorg will fallback to any video class device
> on pci-bus 1.
>
> This fallback actually has been broken in the Xorg xserver for quite a
> while now and only 2 days ago a patch from Laszlo was merged to fix this.
>
> Only for things to break again due to this kernel patch.
>
> Since the whole step 2) thingie is very much tied to x86 machines
> where pci-bus 0 used to be the main bus and pci-bus 1 the agp,
> which is sorta an obsolete assumption now a days and  since relying
> on bus numbers / enumeration order is a bad idea in general I'm not
> entirely sure if this counts as a regression.
>
> I've discussed the problem of the xserver exiting with an error when
> no primary device can be found with some people (ajax) at XDC last week
> since there are other use-cases where the pci-bus 1 fallback does not
> work.
>
> As such I've been working on a xserver patch-set to make the xserver
> try harder (pick the first available device) when both steps described
> above fail to find one, which should make things work even with the
> newest (broken / regressed) kernels.
>
> Given this mail thread, I guess I'm working after all today (I had
> planned a day off) and I'll try to wrap up this patch-set and reply
> to this mail with the server patches attached for Joachim and/or
> Laszlo to test.

Attached are 2 patches against the xserver which should fix this,
please give them a try.

Regards,

Hans

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>From 8499d06529c3f95cf94a6d4429e18d48052c2689 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Fri, 30 Sep 2016 11:59:04 +0200
Subject: [PATCH 1/2] xfree86: Make adding unclaimed devices as GPU devices a
 separate step

This is primarily a preparation patch for fixing the xserver exiting with
a "no screens found" error even though there are supported video cards,
due to the server not recognizing any card as the primary card.

This also fixes the (mostly theoretical) case of a platformBus capable
driver adding a device as GPUscreen before a driver which only supports
the old PCI probe method gets a chance to claim it as a normal screen.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/xfree86/common/xf86Bus.c         |  4 ++++
 hw/xfree86/common/xf86platformBus.c | 15 +++++++++++++++
 hw/xfree86/common/xf86platformBus.h |  6 ++++++
 3 files changed, 25 insertions(+)

diff --git a/hw/xfree86/common/xf86Bus.c b/hw/xfree86/common/xf86Bus.c
index 27c6b1b..a3a9898 100644
--- a/hw/xfree86/common/xf86Bus.c
+++ b/hw/xfree86/common/xf86Bus.c
@@ -125,6 +125,10 @@ xf86BusConfig(void)
         xf86CallDriverProbe(xf86DriverList[i], FALSE);
     }
 
+    for (i = 0; i < xf86NumDrivers; i++) {
+        xf86platformAddGPUDevices(xf86DriverList[i]);
+    }
+
     /* If nothing was detected, return now */
     if (xf86NumScreens == 0) {
         xf86Msg(X_ERROR, "No devices detected.\n");
diff --git a/hw/xfree86/common/xf86platformBus.c b/hw/xfree86/common/xf86platformBus.c
index 3e2264f..ec2a1dd 100644
--- a/hw/xfree86/common/xf86platformBus.c
+++ b/hw/xfree86/common/xf86platformBus.c
@@ -476,6 +476,21 @@ xf86platformProbeDev(DriverPtr drvp)
                                         isGPUDevice(devList[i]) ? PLATFORM_PROBE_GPU_SCREEN : 0);
     }
 
+    return foundScreen;
+}
+
+int
+xf86platformAddGPUDevices(DriverPtr drvp)
+{
+    Bool foundScreen = FALSE;
+    GDevPtr *devList;
+    int j;
+
+    if (!drvp->platformProbe)
+        return FALSE;
+
+    xf86MatchDevice(drvp->driverName, &devList);
+
     /* if autoaddgpu devices is enabled then go find any unclaimed platform
      * devices and add them as GPU screens */
     if (xf86Info.autoAddGPU) {
diff --git a/hw/xfree86/common/xf86platformBus.h b/hw/xfree86/common/xf86platformBus.h
index a7335b9..0f5c0ef 100644
--- a/hw/xfree86/common/xf86platformBus.h
+++ b/hw/xfree86/common/xf86platformBus.h
@@ -41,6 +41,7 @@ struct xf86_platform_device {
 #ifdef XSERVER_PLATFORM_BUS
 int xf86platformProbe(void);
 int xf86platformProbeDev(DriverPtr drvp);
+int xf86platformAddGPUDevices(DriverPtr drvp);
 
 extern int xf86_num_platform_devices;
 extern struct xf86_platform_device *xf86_platform_devices;
@@ -156,6 +157,11 @@ xf86PlatformMatchDriver(char *matches[], int nmatches);
 
 extern void xf86platformVTProbe(void);
 extern void xf86platformPrimary(void);
+
+#else
+
+static inline int xf86platformAddGPUDevices(DriverPtr drvp) { return FALSE; }
+
 #endif
 
 #endif
-- 
2.9.3


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>From 3241fcf1636e1b1cb8e0fdd698a2d2e00d1bbcc0 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Fri, 30 Sep 2016 12:29:09 +0200
Subject: [PATCH 2/2] xfree86: Try harder to find atleast 1 non GPU Screen

If we did not find any non GPU Screens, try again ignoring the notion
of any video devices being the primary device. This fixes Xorg exiting
with a "no screens found" error when using virtio-vga in a
virtual-machine and when using a device driven by simpledrm.

This is a somewhat ugly solution, but it is the best I can come up with
without major surgery to the bus and probe code.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/xfree86/common/xf86.h            |  1 +
 hw/xfree86/common/xf86Bus.c         | 26 +++++++++++++++++++++++---
 hw/xfree86/common/xf86Globals.c     |  1 +
 hw/xfree86/common/xf86pciBus.c      |  4 ++++
 hw/xfree86/common/xf86platformBus.c |  4 ++++
 5 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/hw/xfree86/common/xf86.h b/hw/xfree86/common/xf86.h
index e54c811..f724688 100644
--- a/hw/xfree86/common/xf86.h
+++ b/hw/xfree86/common/xf86.h
@@ -55,6 +55,7 @@
 extern _X_EXPORT int xf86DoConfigure;
 extern _X_EXPORT int xf86DoShowOptions;
 extern _X_EXPORT Bool xf86DoConfigurePass1;
+extern _X_EXPORT Bool xf86ProbeIgnorePrimary;
 extern _X_EXPORT Bool xorgHWAccess;
 
 extern _X_EXPORT DevPrivateKeyRec xf86ScreenKeyRec;
diff --git a/hw/xfree86/common/xf86Bus.c b/hw/xfree86/common/xf86Bus.c
index a3a9898..9836803 100644
--- a/hw/xfree86/common/xf86Bus.c
+++ b/hw/xfree86/common/xf86Bus.c
@@ -117,14 +117,34 @@ xf86BusConfig(void)
     int i, j;
 
     /*
-     * Now call each of the Probe functions.  Each successful probe will
-     * result in an extra entry added to the xf86Screens[] list for each
-     * instance of the hardware found.
+     * 3 step probe to (hopefully) ensure that we always find at least 1
+     * (non GPU) screen:
+     *
+     * 1. Call each drivers probe function normally,
+     *    Each successful probe will result in an extra entry added to the
+     *    xf86Screens[] list for each instance of the hardware found.
      */
     for (i = 0; i < xf86NumDrivers; i++) {
         xf86CallDriverProbe(xf86DriverList[i], FALSE);
     }
 
+    /*
+     * 2. If no Screens were found, call each drivers probe function with
+     *    ignorePrimary = TRUE, to ensure that we do actually get a
+     *    Screen if there is atleast one supported video card.
+     */
+    if (xf86NumScreens == 0) {
+        xf86ProbeIgnorePrimary = TRUE;
+        for (i = 0; i < xf86NumDrivers && xf86NumScreens == 0; i++) {
+            xf86CallDriverProbe(xf86DriverList[i], FALSE);
+        }
+        xf86ProbeIgnorePrimary = FALSE;
+    }
+
+    /*
+     * 3. Call xf86platformAddGPUDevices() to add any additional video cards as
+     *    GPUScreens (GPUScreens are only supported by platformBus drivers).
+     */
     for (i = 0; i < xf86NumDrivers; i++) {
         xf86platformAddGPUDevices(xf86DriverList[i]);
     }
diff --git a/hw/xfree86/common/xf86Globals.c b/hw/xfree86/common/xf86Globals.c
index 072c3fc..0d1e31b 100644
--- a/hw/xfree86/common/xf86Globals.c
+++ b/hw/xfree86/common/xf86Globals.c
@@ -153,6 +153,7 @@ XF86ConfigPtr xf86configptr = NULL;
 Bool xf86Resetting = FALSE;
 Bool xf86Initialising = FALSE;
 Bool xf86DoConfigure = FALSE;
+Bool xf86ProbeIgnorePrimary = FALSE;
 Bool xf86DoShowOptions = FALSE;
 DriverPtr *xf86DriverList = NULL;
 int xf86NumDrivers = 0;
diff --git a/hw/xfree86/common/xf86pciBus.c b/hw/xfree86/common/xf86pciBus.c
index 8158c2b..9adfee5 100644
--- a/hw/xfree86/common/xf86pciBus.c
+++ b/hw/xfree86/common/xf86pciBus.c
@@ -352,6 +352,10 @@ xf86ComparePciBusString(const char *busID, int bus, int device, int func)
 Bool
 xf86IsPrimaryPci(struct pci_device *pPci)
 {
+    /* Add max. 1 screen for the IgnorePrimary fallback path */
+    if (xf86ProbeIgnorePrimary && xf86NumScreens == 0)
+        return TRUE;
+
     if (primaryBus.type == BUS_PCI)
         return pPci == primaryBus.id.pci;
 #ifdef XSERVER_PLATFORM_BUS
diff --git a/hw/xfree86/common/xf86platformBus.c b/hw/xfree86/common/xf86platformBus.c
index ec2a1dd..fde6796 100644
--- a/hw/xfree86/common/xf86platformBus.c
+++ b/hw/xfree86/common/xf86platformBus.c
@@ -115,6 +115,10 @@ xf86_find_platform_device_by_devnum(int major, int minor)
 static Bool
 xf86IsPrimaryPlatform(struct xf86_platform_device *plat)
 {
+    /* Add max. 1 screen for the IgnorePrimary fallback path */
+    if (xf86ProbeIgnorePrimary && xf86NumScreens == 0)
+        return TRUE;
+
     if (primaryBus.type == BUS_PLATFORM)
         return plat == primaryBus.id.plat;
 #ifdef XSERVER_LIBPCIACCESS
-- 
2.9.3


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