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Date: Sat, 19 Jun 2021 22:32:58 -0700
From: Neel Chauhan <nc@FreeBSD.org>
To: Neel Chauhan <nc@freebsd.org>
Cc: Mark Johnston <markj@freebsd.org>, current@freebsd.org
Subject: Re: Kernel/driver hacking: panic: Assertion
 vm_object_busied((m->object)) failed at /usr/src/sys/vm/vm_page.c:5455
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On 2021-06-18 20:03, Neel Chauhan wrote:
> Apparently, the vm_start values is for some reason coming as 0 when it
> is passed into vm_fault_cpu(). That's why it's giving these errors: of
> course the address at 0 is mapped, it is (probably) used by the
> kernel.

An update: The vm_start 0 seems to be expected. I checked the values 
with printf()s.

I have posted this on Twitter, and am considering hiring a kernel 
consultant to help if I am unable to do this on my own.

So I am guessing this line (Line 231) is incorrect:

     pa = sg_dma_address(sgl);

Source: 
https://github.com/neelchauhan/drm-kmod/blob/d0eee96973ee0772e977b813678f92c5becf0507/drivers/gpu/drm/i915/intel_freebsd.c#L231

-Neel (nc@)