[Bug 285853] hv_hid: kernel built with -O0 panics in hv_hid_probe()

From: <bugzilla-noreply_at_freebsd.org>
Date: Thu, 19 Feb 2026 15:40:02 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285853

Zhenlei Huang <zlei@FreeBSD.org> changed:

           What    |Removed                     |Added
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                 CC|                            |kib@FreeBSD.org

--- Comment #3 from Zhenlei Huang <zlei@FreeBSD.org> ---
(In reply to Lexi Winter from comment #0)
Some interesting finding. In x86-64 `00 00` is disassembled to `add   
%al,(%rax)`. So probably 

> (kgdb) disass hv_hid_probe
> Dump of assembler code for function hv_hid_probe:
>   0xffffffff83d11000 <+0>:     add    %al,(%rax)
>   0xffffffff83d11002 <+2>:     add    %al,(%rax)
>   0xffffffff83d11004 <+4>:     add    %al,(%rax)
>   0xffffffff83d11006 <+6>:     add    %al,(%rax)
>   0xffffffff83d11008 <+8>:     add    %al,(%rax)
>   0xffffffff83d1100a <+10>:    add    %al,(%rax)
>   0xffffffff83d1100c <+12>:    add    %al,(%rax)
>   0xffffffff83d1100e <+14>:    (bad)
>   0xffffffff83d1100f <+15>:    loopne 0xffffffff83d11038 <hv_hid_probe+56>

hints a block of the address 0xffffffff83d11000 is filled with zeroes ?

Emm, is it possible the CPU instruction cache is not flushed on loading the
hv_hid.ko module ? 

CC Konstantin for better insights on that.

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