linux-kernel - Re: [PATCH v4 09/18] KVM: arm64: selftests: Add guest support to get the vcpuid

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Message-ID: <CAAeT=Fw0Z1USVpdi2iRMRq0ktTP4+VFzfy31FWV36VPOCTq6_w@mail.gmail.com>
Date:   Sun, 12 Sep 2021 00:05:22 -0700
From:   Reiji Watanabe <reijiw@...gle.com>
To:     Raghavendra Rao Ananta <rananta@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Andrew Jones <drjones@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Peter Shier <pshier@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v4 09/18] KVM: arm64: selftests: Add guest support to get
 the vcpuid

Hi Raghu and all,

On Wed, Sep 8, 2021 at 6:38 PM Raghavendra Rao Ananta
<rananta@...gle.com> wrote:
>
> At times, such as when in the interrupt handler, the guest wants
> to get the vcpuid that it's running on. As a result, introduce
> get_vcpuid() that returns the vcpuid of the calling vcpu. At its
> backend, the VMM prepares a map of vcpuid and mpidr during VM
> initialization and exports the map to the guest for it to read.

How about using TPIDR_EL1 to hold the vcpuid ?
i.e. have aarch64_vcpu_setup() set the register to vcpuid and
guest_get_vcpuid() simply return a value of the register.
This would be a simpler solution to implement.

Thanks,
Reiji