linux-kernel - Re: [RFC PATCH 06/16] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE

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Date:   Tue, 30 Jul 2019 17:38:51 +0530
From:   Anup Patel <anup@...infault.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Anup Patel <Anup.Patel@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Radim K <rkrcmar@...hat.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Christoph Hellwig <hch@...radead.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 06/16] RISC-V: KVM: Implement KVM_GET_ONE_REG/KVM_SET_ONE_REG
 ioctls

On Tue, Jul 30, 2019 at 3:05 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 30/07/19 10:43, Paolo Bonzini wrote:
> > On 29/07/19 13:56, Anup Patel wrote:
> >> The PC register represents program counter whereas the MODE
> >> register represent VCPU privilege mode (i.e. S/U-mode).
> >>
> > Is there any reason to include this pseudo-register instead of allowing
> > SSTATUS access directly in this patch (and perhaps also SEPC)?
>
> Nevermind, I was confused - the current MODE is indeed not accessible as
> a "real" CSR in RISC-V.

Yes, you got it right.

>
> Still, I would prefer all the VS CSRs to be accessible via the get/set
> reg ioctls.

We had implemented VS CSRs access to user-space but then we
removed it to keep this series simple and easy to review. We thought
of adding it later when we deal with Guest/VM migration.

Do you want it to be added as part of this series ?

Regards,
Anup