linux-kernel - Re: [PATCH v7 2/4] arm64: Add BBM Level 2 cpu feature

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: <f9cf869a-7f86-4600-a2d1-b9092551105f@arm.com>
Date: Tue, 17 Jun 2025 11:35:18 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Mikołaj Lenczewski <miko.lenczewski@....com>,
 ryan.roberts@....com, yang@...amperecomputing.com, catalin.marinas@....com,
 will@...nel.org, jean-philippe@...aro.org, robin.murphy@....com,
 joro@...tes.org, maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com,
 james.morse@....com, broonie@...nel.org, ardb@...nel.org, baohua@...nel.org,
 david@...hat.com, jgg@...pe.ca, nicolinc@...dia.com, jsnitsel@...hat.com,
 mshavit@...gle.com, kevin.tian@...el.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 iommu@...ts.linux.dev
Subject: Re: [PATCH v7 2/4] arm64: Add BBM Level 2 cpu feature

On 17/06/2025 10:51, Mikołaj Lenczewski wrote:
> The Break-Before-Make cpu feature supports multiple levels (levels 0-2),
> and this commit adds a dedicated BBML2 cpufeature to test against
> support for.
> 
> To support BBML2 in as wide a range of contexts as we can, we want not
> only the architectural guarantees that BBML2 makes, but additionally
> want BBML2 to not create TLB conflict aborts. Not causing aborts avoids
> us having to prove that no recursive faults can be induced in any path
> that uses BBML2, allowing its use for arbitrary kernel mappings.
> 
> This feature builds on the previous ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE,
> as all early cpus must support BBML2 for us to enable it (and any later
> cpus must also support it to be onlined).
> 
> Not onlining late cpus that do not support BBML2 is unavoidable, as we
> might currently be using BBML2 semantics for kernel memory regions. This
> could cause faults in the late cpus, and would be difficult to unwind,
> so let us avoid the case altogether.
> 
> Signed-off-by: Mikołaj Lenczewski <miko.lenczewski@....com>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>