linux-kernel - Re: [RFC PATCH 04/16] RISC-V: KVM: Implement VCPU create, init and destroy functions

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Date:   Tue, 30 Jul 2019 13:47:49 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Anup Patel <anup@...infault.org>
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 04/16] RISC-V: KVM: Implement VCPU create, init and
 destroy functions

On 30/07/19 13:45, Anup Patel wrote:
>> so:
>>
>> 1) indeed we need SP2V=SPV=1 when entering guest mode
>>
>> 2) sstatus.SPP contains the guest mode
>>
>> 3) SP2P doesn't really matter for KVM since it never goes to VS-mode
>> from an interrupt handler, so if my reasoning is correct I'd leave it
>> clear, but I guess it's up to you whether to set it or not.
> Yes, SP2P does not matter but we set it to 1 here so that from Guest
> perspective it seems we were in S-mode previously.

But the guest never reads sstatus.SPP, it always reads, vsstatus.SPP
doesn't it?  In any case it doesn't matter.

Paolo