[Bug 206299] [nouveau/xen] RTX 20XX instant reboot

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=206299

--- Comment #8 from Frédéric Pierret (frederic.epitre at orange.fr) ---
We found more information!

The previous tests was done with those added lines:

--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
@@ -75,13 +75,25 @@ nv50_disp_chan_mthd(struct nv50_disp_chan *chan, int debug)
        if (debug > subdev->debug)
                return;

+       nvkm_warn(subdev, "mthd: %p", mthd);
+       nvkm_warn(subdev, "mthd->data: %p", mthd->data);
+       nvkm_warn(subdev, "&mthd->data[0]: %p", &mthd->data[0]);
+       nvkm_warn(subdev, "mthd->data[0].mthd: %p", mthd->data[0].mthd);
        for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) {

which gaves as crashlog:

[   45.513617] nouveau 0000:26:00.0: disp: chid 73 stat 00001080 reason 1
[PUSHBUFFER_ERR] mthd 0200 data badf5040 code badf5040
[   45.513633] nouveau 0000:26:00.0: disp: mthd: 00000000dfa55708
[   45.513638] nouveau 0000:26:00.0: disp: mthd->data: 00000000858af80f
[   45.513641] nouveau 0000:26:00.0: disp: &mthd->data[0]: 00000000858af80f

But replacing "%p" by "%lx", it revealed that mthd is NULL:

[   74.753207] nouveau 0000:26:00.0: disp: chid 73 stat 00001080 reason 1
[PUSHBUFFER_ERR] mthd 0200 data badf5040 code badf5040
[   74.753223] nouveau 0000:26:00.0: disp: mthd: 0
[   74.753226] nouveau 0000:26:00.0: disp: mthd->data: 10
[   74.753231] nouveau 0000:26:00.0: disp: &mthd->data[0]: 10
[   74.753241] BUG: kernel NULL pointer dereference, address: 0000000000000020
[   74.753244] #PF: supervisor read access in kernel mode

That gives some hints!

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