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Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes.

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  Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Larry Wei <larryw3i@yeah.net> - 2025-04-24 10:40 +0200
    Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Ben Hutchings <ben@decadent.org.uk> - 2025-04-25 06:00 +0200
    Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-07 21:30 +0200
      Bug#1103397: linux-image-amd64: Kernel Panic:  copy_fpstate_to_sigframe crashes. Salvatore Bonaccorso <carnil@debian.org> - 2025-05-08 22:20 +0200
        Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-09 06:00 +0200
          Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Tony W Wang-oc <TonyWWang-oc@zhaoxin.com> - 2025-05-09 11:10 +0200
            Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-09 11:20 +0200
              Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Tony W Wang-oc <TonyWWang-oc@zhaoxin.com> - 2025-05-09 12:00 +0200
                Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-09 15:40 +0200
        Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-09 06:10 +0200
      Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Ben Hutchings <ben@decadent.org.uk> - 2025-05-09 22:40 +0200
        Processed: Re: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane  crashes. "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-05-09 22:40 +0200
        Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-10 17:10 +0200
        Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-10 18:10 +0200
          Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes. Larry Wei <larryw3i@yeah.net> - 2025-05-10 18:40 +0200
            Bug#1103397: Missing backlight control on Zhaoxin SoC Ben Hutchings <ben@decadent.org.uk> - 2025-05-14 00:30 +0200

#86977 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes.

Thanks for your replying, the `Probe URL` of my laptop: 
https://linux-hardware.org/?probe=58facb533d , and `cpuinfo` is:

larry@zx2:~/Downloads$ sudo cat /proc/cpuinfo
processor    : 0
vendor_id    : CentaurHauls
cpu family    : 7
model        : 59
model name    : ZHAOXIN KaiXian KX-6000G/4@3.0GHz
stepping    : 2
cpu MHz        : 3160.490
cache size    : 4096 KB
physical id    : 0
siblings    : 4
core id        : 0
cpu cores    : 4
apicid        : 0
initial apicid    : 0
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx 
pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl nonstop_tsc 
cpuid aperfmperf pni pclmulqdq monitor vmx smx est tm2 ssse3 cx16 xtpr 
pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c 
rdrand rng rng_en ace ace_en ace2 phe phe_en pmm pmm_en lahf_lm abm 
3dnowprefetch ibrs ibpb tpr_shadow ept vpid fsgsbase tsc_adjust bmi1 
smep bmi2 invpcid rdseed adx smap sha_ni xsaveopt dtherm hwp 
hwp_act_window hwp_epp hwp_pkg_req vnmi umip pku ospke rdpid 
arch_capabilities
vmx flags    : vnmi invvpid ept_x_only ept_1gb tsc_offset vtpr mtf ept 
vpid unrestricted_guest ple
bugs        : spectre_v1
bogomips    : 6586.97
clflush size    : 64
cache_alignment    : 64
address sizes    : 40 bits physical, 48 bits virtual
power management:

processor    : 1
vendor_id    : CentaurHauls
cpu family    : 7
model        : 59
model name    : ZHAOXIN KaiXian KX-6000G/4@3.0GHz
stepping    : 2
cpu MHz        : 3202.559
cache size    : 4096 KB
physical id    : 0
siblings    : 4
core id        : 1
cpu cores    : 4
apicid        : 1
initial apicid    : 1
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx 
pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl nonstop_tsc 
cpuid aperfmperf pni pclmulqdq monitor vmx smx est tm2 ssse3 cx16 xtpr 
pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c 
rdrand rng rng_en ace ace_en ace2 phe phe_en pmm pmm_en lahf_lm abm 
3dnowprefetch ibrs ibpb tpr_shadow ept vpid fsgsbase tsc_adjust bmi1 
smep bmi2 invpcid rdseed adx smap sha_ni xsaveopt dtherm hwp 
hwp_act_window hwp_epp hwp_pkg_req vnmi umip pku ospke rdpid 
arch_capabilities
vmx flags    : vnmi invvpid ept_x_only ept_1gb tsc_offset vtpr mtf ept 
vpid unrestricted_guest ple
bugs        : spectre_v1
bogomips    : 6586.97
clflush size    : 64
cache_alignment    : 64
address sizes    : 40 bits physical, 48 bits virtual
power management:

processor    : 2
vendor_id    : CentaurHauls
cpu family    : 7
model        : 59
model name    : ZHAOXIN KaiXian KX-6000G/4@3.0GHz
stepping    : 2
cpu MHz        : 3206.178
cache size    : 4096 KB
physical id    : 0
siblings    : 4
core id        : 2
cpu cores    : 4
apicid        : 2
initial apicid    : 2
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx 
pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl nonstop_tsc 
cpuid aperfmperf pni pclmulqdq monitor vmx smx est tm2 ssse3 cx16 xtpr 
pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c 
rdrand rng rng_en ace ace_en ace2 phe phe_en pmm pmm_en lahf_lm abm 
3dnowprefetch ibrs ibpb tpr_shadow ept vpid fsgsbase tsc_adjust bmi1 
smep bmi2 invpcid rdseed adx smap sha_ni xsaveopt dtherm hwp 
hwp_act_window hwp_epp hwp_pkg_req vnmi umip pku ospke rdpid 
arch_capabilities
vmx flags    : vnmi invvpid ept_x_only ept_1gb tsc_offset vtpr mtf ept 
vpid unrestricted_guest ple
bugs        : spectre_v1
bogomips    : 6586.97
clflush size    : 64
cache_alignment    : 64
address sizes    : 40 bits physical, 48 bits virtual
power management:

processor    : 3
vendor_id    : CentaurHauls
cpu family    : 7
model        : 59
model name    : ZHAOXIN KaiXian KX-6000G/4@3.0GHz
stepping    : 2
cpu MHz        : 3195.306
cache size    : 4096 KB
physical id    : 0
siblings    : 4
core id        : 3
cpu cores    : 4
apicid        : 3
initial apicid    : 3
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx 
pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl nonstop_tsc 
cpuid aperfmperf pni pclmulqdq monitor vmx smx est tm2 ssse3 cx16 xtpr 
pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c 
rdrand rng rng_en ace ace_en ace2 phe phe_en pmm pmm_en lahf_lm abm 
3dnowprefetch ibrs ibpb tpr_shadow ept vpid fsgsbase tsc_adjust bmi1 
smep bmi2 invpcid rdseed adx smap sha_ni xsaveopt dtherm hwp 
hwp_act_window hwp_epp hwp_pkg_req vnmi umip pku ospke rdpid 
arch_capabilities
vmx flags    : vnmi invvpid ept_x_only ept_1gb tsc_offset vtpr mtf ept 
vpid unrestricted_guest ple
bugs        : spectre_v1
bogomips    : 6586.97
clflush size    : 64
cache_alignment    : 64
address sizes    : 40 bits physical, 48 bits virtual
power management:

Regards,

larryw3i.

On 4/24/25 08:51, Ben Hutchings wrote:
> Control: tag -1 moreinfo
>
> On Thu, 17 Apr 2025 11:57:47 +0800 root <larryw3i@yeah.net> wrote:
>> Package: linux-image-amd64
>> Version: 6.12.22-1
>> Severity: important
>>
>> Dear Maintainer,
>>
>> After linux-image-6.11.9-amd64, my laptop has never booted from linux-image-
>> amd64 any more. It shows "Kernel panic" after Grub. I took a screenshot for
>> that. I do hope you maintainers can SAVE my laptop.
>>
>> The Kernel panic print as follow:
>> --------------------------------------------------------------------------------
>> 0.93186510ops: general protection fault, naybe for address 0x0: 0000 [#1]
>> PREEMPT SMP NOPTI
>> 0.9318931 CPU: 1 UID:0 PID:1 Comn: init Not tainted 6.12.22-and64 #1 Debian
>> 6.12.22-1
>> 0.9319151 Harduare nane: GITSIAR GDC-1461/GM-1461,BIOS 03.04 08/03/2023
>> 0.9319321 RIP: 0010:copy_fpstate_to_sigframe+0x1eb/0x3c0
>> 0.9319521 Code: b9 01 00 00 00 of 01 d0 48 c1 e2 20 89 c0 48 01 c2 48 81 ca ff
>> 02 00 00 49 21 d5 e9 f4 fe ff ff 0f 1f 44 00 00 b9 01 00 0 0 <0f> 01 d0 48 c1
>> e2 20 89 c0 48 8d 8d 00 02 00 00 48 01 d0 4c 21 e8
> We got a #GP exception on an XGETBV instruction, which means "ECX
> specifies a reserved or unimplemented XCR address".  So this instruction
> is wrongly being used on a CPU that doesn't support it.
>
> To help confirm this, please can you send the contents of /proc/cpuinfo?
>
>> 0.9319911 RSP:0018:ffffa6844002bc28EFLAGS:00010246
>> 0.9320061RAX:   0 RBX: 00000000 RcX: 00000001
> [...]
>
> ECX is 1 (= XCR_XFEATURE_IN_USE_MASK).  So this is a use of
> xfeatures_in_use() inlined into copy_fpstate_to_sigframe().
>
> Since this is a regression after 6.11.9, my guess is that this is caused
> by:
>
> commit dd9478d54c738e86692b83cc992dc4fb643bcdbf
> Author: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
> Date:   Tue Nov 19 17:45:20 2024 +0000
>   
>      x86/pkeys: Ensure updated PKRU value is XRSTOR'd
>      
>      [ Upstream commit ae6012d72fa60c9ff92de5bac7a8021a47458e5b ]
>
> which went into 6.12.5 and adds a call to xfeatures_in_use() without an
> obvious CPU feature check.  (The added call is not directly in
> copy_fpstate_to_sigframe() but it's in a function that can be inlined
> into it.)
>
> Ben.
>

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#87015

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Hi Aruna,

Commit ae6012d72fa6 "x86/pkeys: Ensure updated PKRU value is XRSTOR'd"
seems to be broken on some Zhaoxin/VIA processors.  Specifically:

On Thu, 2025-04-24 at 16:24 +0800, Larry Wei wrote:
> Thanks for your replying, the `Probe URL` of my laptop: 
> https://linux-hardware.org/?probe=58facb533d , and `cpuinfo` is:
> 
> larry@zx2:~/Downloads$ sudo cat /proc/cpuinfo
> processor    : 0
> vendor_id    : CentaurHauls
> cpu family    : 7
> model        : 59
> model name    : ZHAOXIN KaiXian KX-6000G/4@3.0GHz
[...]
> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
> cmov pat pse36 clflush acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx 
> pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good nopl nonstop_tsc 
> cpuid aperfmperf pni pclmulqdq monitor vmx smx est tm2 ssse3 cx16 xtpr 
> pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c 
> rdrand rng rng_en ace ace_en ace2 phe phe_en pmm pmm_en lahf_lm abm 
> 3dnowprefetch ibrs ibpb tpr_shadow ept vpid fsgsbase tsc_adjust bmi1 
> smep bmi2 invpcid rdseed adx smap sha_ni xsaveopt dtherm hwp 
> hwp_act_window hwp_epp hwp_pkg_req vnmi umip pku ospke rdpid 
> arch_capabilities
> vmx flags    : vnmi invvpid ept_x_only ept_1gb tsc_offset vtpr mtf ept 
> vpid unrestricted_guest ple
[...]

Notice that this has the PKU and OSPKE features set, but *not* XGETBV1.
Which means that xfeatures_in_use() should not be called (and will cause
a #GP exception).

(The full bug report log for this is at
<https://bugs.debian.org/1103397>.)

Is there some fallback that could be used in case XGETBV1 is not
available?  Or do we need a dependency X86_FEATURE_PKU ->
X86_FEATURE_XGETBV1 in arch/x86/kernel/cpu/cpuid-deps.c, so that we
disable protection keys in this CPU?
> 
> 

Ben.

-- 
Ben Hutchings
Who are all these weirdos? - David Bowie, on joining IRC

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#87446

[Multipart message — attachments visible in raw view] — view raw

Thank you all,

I have pulled the newest `linux-next` changes and compiled it, my laptop 
boots well now! https://linux-hardware.org/?probe=271fabb7a4 , but it 
still prints some `WARNING` information at startup: 
https://linux-hardware.org/?probe=271fabb7a4&log=dmesg . May this output 
is useful for you maintainers.

And, thank you all again.

Regards,

larryw3i

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#87471 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

Hi Larry Wei, hi Ben,

For context this is about https://bugs.debian.org/1103397, and which
Ben did forward in
https://lore.kernel.org/regressions/dddb6b8d56e3f28b914e1e243f948457d53149ce.camel@decadent.org.uk/T/

On Thu, May 08, 2025 at 03:12:31AM +0800, Larry Wei wrote:
> Thank you all,
> 
> I have pulled the newest `linux-next` changes and compiled it, my laptop
> boots well now! https://linux-hardware.org/?probe=271fabb7a4 , but it still
> prints some `WARNING` information at startup:
> https://linux-hardware.org/?probe=271fabb7a4&log=dmesg . May this output is
> useful for you maintainers.
> 
> And, thank you all again.

Going thorough the bugs I notice there was a related upstream
discussion/patch relating to ae6012d72fa6 ("x86/pkeys: Ensure updated
PKRU value is XRSTOR'd")  in the following:

https://lore.kernel.org/all/20250102075419.2559-1-TonyWWang-oc@zhaoxin.com/

There were some followups, but discussion ended on 18.01.2025.

Did this felt through the cracks?

Regards,
Salvatore

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#87473 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

Salvatore Bonaccorso,

Yes, let's just consider it as good. But in fact, there are still many 
problems, such as the one mentioned above ( 
linux-hardware.org/?probe=271fabb7a4&log=dmesg ), and almost all laptops 
using Zhaoxin CPUs cannot adjust the backlight brightness, which is 
**VERY HARMFUL** to the eyes!

Regards,

larryw3i

On 5/9/25 04:15, Salvatore Bonaccorso wrote:
> Did this felt through the cracks?

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#87476 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

On 2025/5/9 11:49, Larry Wei wrote:
> 
> 
> [这封邮件来自外部发件人 谨防风险]
> 
> Salvatore Bonaccorso,
> 
> Yes, let's just consider it as good. But in fact, there are still many
> problems, such as the one mentioned above (
> linux-hardware.org/?probe=271fabb7a4&log=dmesg ), and almost all laptops
> using Zhaoxin CPUs cannot adjust the backlight brightness, which is
> **VERY HARMFUL** to the eyes!

Dear Larry,

We are currently investigating the causes of the WARNING messages you 
mentioned in this log:
[    4.141284] ------------[ cut here ]------------
[    4.141285] alg: self-tests for sha1 using sha1-padlock-nano failed 
(rc=-22)
[    4.141302] WARNING: CPU: 2 PID: 657 at crypto/testmgr.c:5865 
alg_test.cold+0xb7/0xe0

Regarding the inability to adjust the laptop backlight brightness, we 
believe this issue is unlikely related to the CPU itself. It is 
recommended to contact the laptop manufacturer to confirm whether the 
device supports backlight brightness adjustment and inquire about 
specific configuration methods, such as installing specific EC 
controller drivers or updating graphics card drivers.

BRs!
TonyWWang-oc
> 
> Regards,
> 
> larryw3i
> 
> On 5/9/25 04:15, Salvatore Bonaccorso wrote:
>> Did this felt through the cracks?
> 

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#87477 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

Dear TonyWWang-oc,

Yes, but actually, these graphics cards are your products, and neither 
C-960 nor C-1080 seem to be open source.The drivers provided on your 
official website do not seem to be used for Debian.I downloaded your 
drivers and extracted them, and I found that each file has the license 
content.Can I assume that these drivers are open source?

Regards,

larryw3i

On 5/9/25 16:31, Tony W Wang-oc wrote:
> such as installing specific EC controller drivers or updating graphics 
> card drivers. 

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#87478 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

On 2025/5/9 17:08, Larry Wei wrote:
> 
> 
> [这封邮件来自外部发件人 谨防风险]
> 
> Dear TonyWWang-oc,
> 
> Yes, but actually, these graphics cards are your products, and neither
> C-960 nor C-1080 seem to be open source.The drivers provided on your
> official website do not seem to be used for Debian.I downloaded your
> drivers and extracted them, and I found that each file has the license
> content.Can I assume that these drivers are open source?
> 

Dear Larry,

The graphics driver package contains both kernel-mode and user-mode
components, where the kernel-mode components are open source, while
graphics rendering tasks predominantly rely on user-mode implementations.

BRs!
TonyWWang-oc


> Regards,
> 
> larryw3i
> 
> On 5/9/25 16:31, Tony W Wang-oc wrote:
>> such as installing specific EC controller drivers or updating graphics
>> card drivers.
> 

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#87480 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

[Multipart message — attachments visible in raw view] — view raw

😮‍💨👌 .

On 5/9/25 17:53, Tony W Wang-oc wrote:
> hile
> graphics rendering tasks predominantly rely on user-mode implementations.

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#87474 — Bug#1103397: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigframe crashes.

Salvatore Bonaccorso,

Yes, let's just consider it as good. But in fact, there are still many 
problems, such as the one mentioned above ( 
linux-hardware.org/?probe=271fabb7a4&log=dmesg ), and almost all laptops 
using Zhaoxin CPUs cannot adjust the backlight brightness, which is 
**VERY HARMFUL** to the eyes!

Regards,

larryw3i

[toc] | [prev] | [next] | [standalone]

#87485

[Multipart message — attachments visible in raw view] — view raw

Control: tag -1 patch

On Thu, 2025-05-08 at 03:12 +0800, Larry Wei wrote:
> Thank you all, 
> 
> I have pulled the newest `linux-next` changes and compiled it, my
> laptop boots well now! https://linux-hardware.org/?probe=271fabb7a4 ,
[...]

Looking at what has changed in linux-next, this appears to be the fix:

commit d1e420772cd1eb0afe5858619c73ce36f3e781a1
Author: Chang S. Bae <chang.seok.bae@intel.com>
Date:   Tue Apr 15 19:16:58 2025 -0700
 
    x86/pkeys: Simplify PKRU update in signal frame

This is currently in the tip tree but won't go to Linus until after the
6.15 release.

As this fixes a regression on real CPUs, it should not need to wait for
the next release cycle, right?


Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption]
would be development of an easy way to factor large prime numbers.
                                                           - Bill Gates

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#87486 — Processed: Re: linux-image-amd64: Kernel Panic: copy_fpstate_to_sigfrane crashes.

Processing control commands:

> tag -1 patch
Bug #1103397 [src:linux] Kernel Panic: copy_fpstate_to_sigframe crashes
Bug #1103399 [src:linux] Kernel Panic: copy_fpstate_to_sigframe crashes
Added tag(s) patch.
Added tag(s) patch.

-- 
1103397: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1103397
1103399: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1103399
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems

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#87519

Hi! Ben,

It will be OK! I don't think there are many people using this type of 
machine, after all, they can't even adjust the backlight, and I don't 
think anyone likes to use this type of machine, and they also like to 
use it to install Debian. I am very happy that this issue can be fixed. 
For now, I just need to use the kernel I compiled myself.
Thank you all.

Regards,

larryw3i

On 5/10/25 04:33, Ben Hutchings wrote:
>   it should not need to wait for
> the next release cycle, right?

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#87520

Ben,

I remember two years ago, it seemed like the backlight of this laptop 
could be adjusted. At that time, I installed Ubuntu on this laptop and 
there seemed to be a directory called "acpi_video" in the 
"/sys/class/backlight/" directory. However, at some point, this 
directory no longer existed. At that time, I was not very familiar with 
Linux distributions and didn't know how to report bugs.

Regards,

larryw3i

On 5/10/25 04:33, Ben Hutchings wrote:
> Looking at what has changed in linux-next, this appears to be the fix:

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#87521

P.S. And I suspect that this change has been affecting all non-Intel and 
non-AMD machines for a long time, as there is no "non-free-firmware" 
suitable for them.

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#87561 — Bug#1103397: Missing backlight control on Zhaoxin SoC

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On Sun, 2025-05-11 at 00:28 +0800, Larry Wei wrote:
> P.S. And I suspect that this change has been affecting all non-Intel and 
> non-AMD machines for a long time, as there is no "non-free-firmware" 
> suitable for them.

No, not quite.

By default the ACPI video driver relies on the native graphics driver to
detect which display(s) have a backlight, and to decide whether they
should be controlled via ACPI or via the display controller.

According to <https://linux-hardware.org/?probe=58facb533d> there is no
native driver loaded on your system for the graphics device.  Probably
the EFI framebuffer driver is being used instead.  This has no knowledge
of what kind of display is being used and cannot configure the ACPI
video driver properly.

So the real fix for this would be for Zhaoxin to get their Linux
graphics driver (zx) upstream.  The immediate problem I see with that is
that it's under GPL v3 which is not compatible with the kernel's GPL v2.
But they as copyright holder should be able to relicense it.

Ben.

-- 
Ben Hutchings
Tomorrow will be cancelled due to lack of interest.

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