[REGRESSION] drm/etnaviv: command buffer outside valid memory window

[Russell King - ARM Linux admin]

On Thu, Jun 27, 2019 at 11:20:15AM +0200, Lucas Stach wrote:
> Am Samstag, den 22.06.2019, 17:16 +0100 schrieb Russell King - ARM Linux admin:
> > While updating my various systems for the TCP SACK issue, I notice
> > that while most platforms are happy, the Cubox-i4 is not.  During
> > boot, we get:
> > 
> > [    0.000000] cma: Reserved 256 MiB at 0x30000000
> > ...
> > [    0.000000] Kernel command line: console=ttymxc0,115200n8 console=tty1 video=mxcfb0:dev=hdmi root=/dev/nfs rw cma=256M ahci_imx.hotplug=1 splash resume=/dev/sda1
> > [    0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
> > [    0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
> > [    0.000000] Memory: 1790972K/2097152K available (8471K kernel code, 693K rwdata, 2844K rodata, 500K init, 8062K bss, 44036K reserved, 262144K cma-reserved, 1310720K highmem)
> > ...
> > [   13.101098] etnaviv-gpu 130000.gpu: command buffer outside valid memory window
> > [   13.171963] etnaviv-gpu 134000.gpu: command buffer outside valid memory window
> 
> Yes, that's a regression due to different default CMA area placement
> and etnaviv not being smart enough to move the linear window to the
> right offset.

As it's a user visible regression, it needs fixing, either by reverting
the changes that caused it or by some other issue.  In the kernel, the
policy is "if a bug fix causes a regression, the bug fix was itself
wrong".  We don't fix one person's bug if it causes a regression for
someone else.

Please resolve the acknowledged regression.

> > and shortly after the login prompt appears, the entire SoC appears to
> > lock up - it becomes unresponsive on the network, or via serial console
> > to sysrq requests.
> > 
> > I suspect the GPU ends up scribbling over the CPU's vector page/kernel
> > as a result of the above two etnaviv errors when Xorg attempts to start
> > using the GPU.
> 
> This should not be possible. The driver notices that the command buffer
> isn't accessible to the GPU, which aborts the GPU init. While the
> etnaviv DRM device is still accessible, it will not expose any
> enumerable GPU cores to userspace. So there is no way for userspace to
> actually submit GPU commands.

Yep, I came to that conclusion.  Nevertheless, if I allow Xorg to start
with 5.1, the system totally hangs shortly thereafter.  I need to try
without etnaviv loaded at all.

-- 
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