On Wed, Jan 29, 2020 at 05:22:13PM +0100, Frédéric Pierret wrote:

Dear Ben Skeggs,

Please find attached a patch solving a blocking issue I encountered: https://bugzilla.kernel.org/show_bug.cgi?id=206299

Basically, running at least a RTX2080TI on Xen makes a bad mmio error which causes having 'mthd' pointer to be NULL in 'channv50.c'. From the code, it's assumed to be not NULL by accessing directly 'mthd->data[0]' which is the reason of the kernel panic. I simply check if the pointer is not NULL before continuing.

Best regards,

Frédéric Pierret

From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Pierret=20=28fepitre=29?= frederic.pierret@qubes-os.org Date: Sun, 26 Jan 2020 23:24:33 +0100 Subject: [PATCH] nv50_disp_chan_mthd: ensure mthd is not NULL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

Pointer to structure array is assumed not NULL by default. It has the consequence to raise a kernel panic when it's not the case.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206299 Signed-off-by: Frédéric Pierret (fepitre) frederic.pierret@qubes-os.org

---

drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c index bcf32d92ee5a..50e3539f33d2 100644 --- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c +++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c @@ -74,6 +74,8 @@ nv50_disp_chan_mthd(struct nv50_disp_chan *chan, int debug) if (debug > subdev->debug) return;

• if (!mthd)

• return;
  

for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) { u32 base = chan->head * mthd->addr; -- 2.21.0

<formletter>

This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.

</formletter>