linux-kernel - Re: [PATCH v3 0/5] arch_topology: Build cacheinfo from primary CPU

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Message-ID: <0f19cb3f-d6cf-4032-66d2-dedc9d09a0e3@linaro.org>
Date:   Thu, 29 Dec 2022 17:47:44 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Pierre Gondois <pierre.gondois@....com>,
        linux-kernel@...r.kernel.org
Cc:     palmer@...osinc.com, Ionela.Voinescu@....com,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Gavin Shan <gshan@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 0/5] arch_topology: Build cacheinfo from primary CPU

On 09/12/2022 11:31, Pierre Gondois wrote:
> v2:
>  - Applied renaming/formatting comments from v1.
>  - Check CACHE_TYPE_VALID flag in pppt.c.
> v3:
>  - Applied Sudeep's suggestions (for patch 5/5):
>    - Renaming allocate_cache_info() -> fecth_cache_info()
>    - Updated error message
>    - Extract an inline allocate_cache_info() function
>  - Re-run checkpatch with --strict option
> 
> Note:
> This patchset requires the following patch to be applied first in
> order to avoid the same bug described in the commit message:
> https://lore.kernel.org/all/20221116094958.2141072-1-pierre.gondois@arm.com/
> 
> [1] and [2] build the CPU topology from the cacheinfo information for
> both DT/ACPI based systems and remove (struct cpu_topology).llc_id
> which was used by ACPI only.
> 
> Creating the cacheinfo for secondary CPUs is done during early boot.
> Preemption and interrupts are disabled at this stage. On PREEMPT_RT
> kernels, allocating memory (and parsing the PPTT table for ACPI based
> systems) triggers a:
>   'BUG: sleeping function called from invalid context' [4]
> 
> To prevent this bug, allocate the cacheinfo from the primary CPU when
> preemption and interrupts are enabled and before booting secondary
> CPUs. The cache levels/leaves are computed from DT/ACPI PPTT information
> only, without relying on the arm64 CLIDR_EL1 register.
> If no cache information is found in the DT/ACPI PPTT, then fallback
> to the current state, triggering [4] on PREEMPT_RT kernels.
> 
> Patches to update the arm64 device trees that have incomplete cacheinfo
> (mostly for missing the 'cache-level' or 'cache-unified' property)
> have been sent at [3].
> 
> Tested platforms:
> - ACPI + PPTT: Ampere Altra, Ampere eMAG, Cavium ThunderX2,
>   Kunpeng 920, Juno-r2
> - DT: rb5, db845c, Juno-r2
> 

I gave the patchset a try with DTS fixes for cache topology on Qualcomm
RB5 board (SM8250 SoC) and with KASAN it produces:

BUG: KASAN: slab-out-of-bounds in populate_cache_leaves+0x84/0x15c
[    0.633014]  dump_backtrace.part.0+0xe0/0xf0
[    0.633035]  show_stack+0x18/0x40
[    0.633050]  dump_stack_lvl+0x8c/0xb8
[    0.633085]  print_report+0x188/0x488
[    0.633106]  kasan_report+0xac/0xf0
[    0.633136]  __asan_store4+0x80/0xa4
[    0.633158]  populate_cache_leaves+0x84/0x15c
[    0.633181]  detect_cache_attributes+0xc0/0x8c4
[    0.633213]  update_siblings_masks+0x28/0x43c
[    0.633235]  store_cpu_topology+0x98/0xc0
[    0.633251]  smp_prepare_cpus+0x2c/0x15c
[    0.633281]  kernel_init_freeable+0x22c/0x424
[    0.633310]  kernel_init+0x24/0x13c
[    0.633328]  ret_from_fork+0x10/0x20
[    0.633388]
[    0.708729] Allocated by task 1:
[    0.712078]  kasan_save_stack+0x2c/0x60
[    0.716066]  kasan_set_track+0x2c/0x40
[    0.719959]  kasan_save_alloc_info+0x24/0x3c
[    0.724387]  __kasan_kmalloc+0xa0/0xbc
[    0.728278]  __kmalloc+0x74/0x110
[    0.731740]  fetch_cache_info+0x170/0x210
[    0.735902]  init_cpu_topology+0x254/0x2bc
[    0.740171]  smp_prepare_cpus+0x20/0x15c
[    0.744272]  kernel_init_freeable+0x22c/0x424
[    0.748791]  kernel_init+0x24/0x13c
[    0.752420]  ret_from_fork+0x10/0x20

Best regards,
Krzysztof

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