linux-kernel - Re: [PATCH 4.9 00/25] 4.9.316-rc1 review

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Date:   Tue, 24 May 2022 11:42:14 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, torvalds@...ux-foundation.org,
        akpm@...ux-foundation.org, linux@...ck-us.net, shuah@...nel.org,
        patches@...nelci.org, lkft-triage@...ts.linaro.org, pavel@...x.de,
        sudipm.mukherjee@...il.com, slade@...dewatkins.com,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 4.9 00/25] 4.9.316-rc1 review

On 5/24/22 10:50, Jon Hunter wrote:
> 
> On 24/05/2022 17:30, Florian Fainelli wrote:
> 
> ...
> 
>> Jonathan any chance this is Tegra specific? Our ARCH_BRCMSTB SoCs 
>> which use a Brahma-B15 which uses nearly the same ca15 processor 
>> functions defined in arch/arm/mm/proc-v7.S reports the following 
>> *before* changes:
>>
>> [    0.001641] CPU: Testing write buffer coherency: ok
>> [    0.001685] CPU0: Spectre v2: using ICIALLU workaround
>> [    0.001703] ftrace: allocating 30541 entries in 120 pages
>> [    0.044600] CPU0: update cpu_capacity 1024
>> [    0.044633] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
>> [    0.044662] Setting up static identity map for 0x200000 - 0x200060
>> [    0.047410] brcmstb: biuctrl: MCP: Write pairing already disabled
>> [    0.048974] CPU1: update cpu_capacity 1024
>> [    0.048978] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
>> [    0.048981] CPU1: Spectre v2: using ICIALLU workaround
>> [    0.050234] CPU2: update cpu_capacity 1024
>> [    0.050238] CPU2: thread -1, cpu 2, socket 0, mpidr 80000002
>> [    0.050241] CPU2: Spectre v2: using ICIALLU workaround
>> [    0.051437] CPU3: update cpu_capacity 1024
>> [    0.051441] CPU3: thread -1, cpu 3, socket 0, mpidr 80000003
>> [    0.051444] CPU3: Spectre v2: using ICIALLU workaround
>> [    0.051532] Brought up 4 CPUs
>>
>> and this *after* merging 4.9.316-rc1:
>>
>> [    0.001626] CPU: Testing write buffer coherency: ok
>> [    0.001670] CPU0: Spectre v2: using ICIALLU workaround
>> [    0.001689] CPU0: Spectre BHB: using loop workaround
>> [    0.001705] ftrace: allocating 30542 entries in 120 pages
>> [    0.043752] CPU0: update cpu_capacity 1024
>> [    0.043784] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
>> [    0.043813] Setting up static identity map for 0x200000 - 0x200060
>> [    0.046547] brcmstb: biuctrl: MCP: Write pairing already disabled
>> [    0.048121] CPU1: update cpu_capacity 1024
>> [    0.048124] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
>> [    0.048129] CPU1: Spectre v2: using ICIALLU workaround
>> [    0.048165] CPU1: Spectre BHB: using loop workaround
>> [    0.049398] CPU2: update cpu_capacity 1024
>> [    0.049402] CPU2: thread -1, cpu 2, socket 0, mpidr 80000002
>> [    0.049405] CPU2: Spectre v2: using ICIALLU workaround
>> [    0.049440] CPU2: Spectre BHB: using loop workaround
>> [    0.050613] CPU3: update cpu_capacity 1024
>> [    0.050617] CPU3: thread -1, cpu 3, socket 0, mpidr 80000003
>> [    0.050619] CPU3: Spectre v2: using ICIALLU workaround
>> [    0.050653] CPU3: Spectre BHB: using loop workaround
>> [    0.050722] Brought up 4 CPUs
>> [    0.050738] SMP: Total of 4 processors activated (216.00 BogoMIPS).
>> [    0.050753] CPU: All CPU(s) started in HYP mode.
> 
> 
> Does your platform support CPU idle? I see this being triggered
> during CPU idle transitions ...

It does, but not with an idle state resulting in powering down secondary 
cores. We do have CPU hotplug with power gating as well as system wide 
suspend states that result in power gating secondaries and they appear 
to be working fine.

I use the attached script to randomly cycle hot plug/unplug through each 
4 cores and it has been running over 10k cycles.

> 
> [    4.415167] CPU0: Spectre BHB: using loop workaround
> [    4.417621] [<c01109a0>] (unwind_backtrace) from [<c010b7ac>] 
> (show_stack+0x10/0x14)
> [    4.430291] [<c010b7ac>] (show_stack) from [<c09c2b38>] 
> (dump_stack+0xc0/0xd4)
> [    4.437512] [<c09c2b38>] (dump_stack) from [<c011a6c8>] 
> (cpu_v7_spectre_bhb_init+0xd8/0x190)
> [    4.445943] [<c011a6c8>] (cpu_v7_spectre_bhb_init) from [<c010dee8>] 
> (cpu_suspend+0xac/0xc8)
> [    4.454377] [<c010dee8>] (cpu_suspend) from [<c011e7e4>] 
> (tegra114_idle_power_down+0x74/0x78)
> [    4.462898] [<c011e7e4>] (tegra114_idle_power_down) from [<c06d3b44>] 
> (cpuidle_enter_state+0x130/0x524)
> [    4.472286] [<c06d3b44>] (cpuidle_enter_state) from [<c0164a30>] 
> (do_idle+0x1b0/0x200)
> [    4.480199] [<c0164a30>] (do_idle) from [<c0164d28>] 
> (cpu_startup_entry+0x18/0x1c)
> [    4.487762] [<c0164d28>] (cpu_startup_entry) from [<801018cc>] 
> (0x801018cc)
> 
> Jon
> 


-- 
Florian
Download attachment "hotplug.sh" of type "application/x-shellscript" (699 bytes)