linux-kernel - Re: [RFC PATCH v2 10/19] RISC-V: KVM: Handle WFI exits for VCPU

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Message-ID: <CAAhSdy02bZAbyK4TGzO0jYRCTCFwexzA_iu7GNRh-07NZ6fuFw@mail.gmail.com>
Date:   Mon, 5 Aug 2019 12:48:12 +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 v2 10/19] RISC-V: KVM: Handle WFI exits for VCPU

On Mon, Aug 5, 2019 at 12:44 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 05/08/19 09:12, Anup Patel wrote:
> > On Fri, Aug 2, 2019 at 2:33 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
> >>
> >> On 02/08/19 09:47, Anup Patel wrote:
> >>> +             if (!kvm_riscv_vcpu_has_interrupt(vcpu)) {
> >>
> >> This can be kvm_arch_vcpu_runnable instead, since kvm_vcpu_block will
> >> check it anyway before sleeping.
> >
> > I think we can skip this check here because kvm_vcpu_block() is
> > checking it anyway. Agree ??
>
> Yes, but it's quite a bit faster to do this outside the call.  There's a
> bunch of setup before kvm_vcpu_block reaches that point, and it includes
> mfences too once you add srcu_read_unlock/lock here.

No problem, I will use kvm_arch_vcpu_runnable() here.

Regards,
Anup