linux-kernel - Re: [PATCH] KVM: arm64: Add big.LITTLE architecture support for vcpu

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Message-ID: <87h7lpzu43.wl-maz@kernel.org>
Date:   Fri, 05 Mar 2021 12:02:20 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Yejune Deng <yejune.deng@...il.com>
Cc:     james.morse@....com, julien.thierry.kdev@...il.com,
        suzuki.poulose@....com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: Add big.LITTLE architecture support for vcpu

On Fri, 05 Mar 2021 10:34:25 +0000,
Yejune Deng <yejune.deng@...il.com> wrote:
> 
> In big.LITTLE architecture,the application layer calls KVM_ARM_VCPU_INIT
> several times.Sometimes the thread will run on the big core, sometimes
> will run on the little core.The big core and the little core has always
> different cpuid, but the init target is fixed. and that leads to
> init->target != phys_target. So modify phys target from the current core
> to all cpu online.

This is done on purpose, and it is userspace's responsibility to pin
its vcpu threads to a certain type of CPUs if it cares at all.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.