Re: [PATCH 00/19] arm64: Implement parallel CPU onlining with PSCI v0.2+

[Pankaj Patil <pankaj.patil@oss.qualcomm.com>]

On 9/7/2026 10:10 PM, Will Deacon wrote:
> Hi folks,
> 
> This series implements CONFIG_HOTPLUG_PARALLEL for arm64 by utilising
> the argument to CPU_ON introduced in PSCI v0.2. This supersedes the
> previous series from Jinjie [1], and I'm grateful to him for his support
> getting this alternative version in shape for posting.
> 
> I previously spoke at KVM forum about this work last year:
> 
>   https://www.youtube.com/watch?v=Q6kOshnnQuE
> 
> There are three major benefits realised by these changes:
> 
> 1. We ditch our home-brew secondary CPU synchronisation in favour of
>    constructs in the core code.
> 
> 2. They offer a performance advantage on some platforms, where getting a
>    CPU into the kernel can take time. I'm hoping Jinjie can provide
>    numbers in this case.
> 

Tested on Glymur-CRD - 18 core qcom,oryon-2-2 CPU, saw ~6% improvement
in smp bringup and ~12% improvement in cpu hotplug kselftest

Tested-by: Pankaj Patil <pankaj.patil@oss.qualcomm.com>
> 3. When used inside a confidential guest, they provide protection
>    against a malicious VMM that puts secondary CPUs into the guest
>    kernel after the onlining operation has timed out.
> 
> The first four patches are small changes to the generic code to make it
> a little more "Arm-shaped" but the rest of the series is largely
> confined to the arm64 architecture and PSCI driver code.[...]