linux-kernel - Re: [PATCH v6 3/5] fbdev: Disable sysfb device registration when removing conflicting FBs

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Date:   Thu, 16 Jun 2022 21:55:24 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Zack Rusin <zackr@...are.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "kraxel@...hat.com" <kraxel@...hat.com>,
        "tzimmermann@...e.de" <tzimmermann@...e.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "daniel.vetter@...ll.ch" <daniel.vetter@...ll.ch>,
        "lersek@...hat.com" <lersek@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "deller@....de" <deller@....de>,
        Linux-graphics-maintainer <Linux-graphics-maintainer@...are.com>
Subject: Re: [PATCH v6 3/5] fbdev: Disable sysfb device registration when
 removing conflicting FBs

Hello Zack,

On 6/16/22 21:29, Zack Rusin wrote:
> On Tue, 2022-06-07 at 20:23 +0200, Javier Martinez Canillas wrote:
>> The platform devices registered by sysfb match with firmware-based DRM or
>> fbdev drivers, that are used to have early graphics using a framebuffer
>> provided by the system firmware.
>>

[snip]

> 
> Hi, Javier.
> 
> This change broke arm64 with vmwgfx. We get a kernel oops at boot (let me know if
> you'd like .config or just have us test something directly for you):
>

Yes please share your .config and I'll try to reproduce on an arm64 machine.

> 
>  Unable to handle kernel NULL pointer dereference at virtual address
> 0000000000000008
>  Mem abort info:
>    ESR = 0x96000004
>    EC = 0x25: DABT (current EL), IL = 32 bits
>    SET = 0, FnV = 0
>    EA = 0, S1PTW = 0
>    FSC = 0x04: level 0 translation fault
>  Data abort info:
>    ISV = 0, ISS = 0x00000004
>    CM = 0, WnR = 0
>  user pgtable: 4k pages, 48-bit VAs, pgdp=00000001787ee000
>  [0000000000000008] pgd=0000000000000000, p4d=0000000000000000
>  Internal error: Oops: 96000004 [#1] SMP
>  Modules linked in: vmwgfx(+) e1000e(+) nvme ahci(+) xhci_pci drm_ttm_helper ttm
> sha256_arm64 sha1_ce nvme_core xhci_pci_renesas aes_neon_bs aes_neon_blk aes>
>  CPU: 3 PID: 215 Comm: systemd-udevd Tainted: G     U            5.18.0-rc5-vmwgfx
> #12

I'm confused, your kernel version seems to be 5.18.0-rc5 but this patch
is only in drm-misc-next now and will land in 5.20...

Did you backport it? Can you please try to reproduce with latest drm-tip ?

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat