linux-kernel - Re: [PATCH] arm64: dts: qcom: x1e: bus is 40-bits (fix 64GB models)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <e6b0aedb-955a-5883-524c-f602ca619681@marek.ca>
Date: Fri, 16 Jan 2026 18:45:54 -0500
From: Jonathan Marek <jonathan@...ek.ca>
To: Bjorn Andersson <andersson@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, Konrad Dybcio <konradybcio@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Sibi Sankar <sibi.sankar@....qualcomm.com>,
 Rajendra Nayak <quic_rjendra@...cinc.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Abel Vesa <abelvesa@...nel.org>
Subject: Re: [PATCH] arm64: dts: qcom: x1e: bus is 40-bits (fix 64GB models)

On 1/16/26 6:19 PM, Bjorn Andersson wrote:
> On Fri, Jan 16, 2026 at 05:53:59PM -0500, Jonathan Marek wrote:
>> It turns out this change will make things worse for the (unfortunately
>> common) EL1+64GB+brokenfirmware case.
>>
>> Because of that I think the Fixes: tag and "(fix 64GB models)" should be
>> dropped from the commit message. (I can also send a v2 with extra info in
>> the commit message if needed)
>>
> 
> It seems to me that neither of these to actions will affect the impact
> of the patch. What does "make things worse" imply?
> 

 From what Stephan wrote [1]: Without this change, devices that use 
SMMUv3 (PCIe) use bounce buffers for memory outside the 36-bit range. 
With this change they won't use SWIOTLB and it will crash instead. (it 
would still crash for other reasons without this change)

[1] https://patchwork.kernel.org/comment/26681014/

> Are we better off dropping this patch?

This patch gets EL2+64GB (and presumably EL1 as well if OEM provides 
updated EL2 firmware) working without crashes. That's better than having 
all 64GB cases be broken.

> 
> Regards,
> Bjorn
> 
>> On 1/16/26 4:39 PM, Bjorn Andersson wrote:
>>>
>>> On Thu, 27 Nov 2025 16:29:42 -0500, Jonathan Marek wrote:
>>>> Unlike the phone SoCs this was copied from, x1e has a 40-bit physical bus.
>>>> The upper address space is used to support more than 32GB of memory.
>>>>
>>>> This fixes issues when DMA buffers are allocated outside the 36-bit range.
>>>>
>>>>
>>>
>>> Applied, thanks!
>>>
>>> [1/1] arm64: dts: qcom: x1e: bus is 40-bits (fix 64GB models)
>>>         commit: b38dd256e11a4c8bd5a893e11fc42d493939c907
>>>
>>> Best regards,
>>>