linux-kernel - Re: [RFC PATCH 00/16] KVM RISC-V Support

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Date:   Tue, 30 Jul 2019 10:56:33 +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 00/16] KVM RISC-V Support

On Tue, Jul 30, 2019 at 3:17 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 29/07/19 13:56, Anup Patel wrote:
> > This series adds initial KVM RISC-V support. Currently, we are able to boot
> > RISC-V 64bit Linux Guests with multiple VCPUs.
> >
> > Few key aspects of KVM RISC-V added by this series are:
> > 1. Minimal possible KVM world-switch which touches only GPRs and few CSRs.
> > 2. Full Guest/VM switch is done via vcpu_get/vcpu_put infrastructure.
> > 3. KVM ONE_REG interface for VCPU register access from user-space.
> > 4. PLIC emulation is done in user-space. In-kernel PLIC emulation, will
> >    be added in future.
> > 5. Timer and IPI emuation is done in-kernel.
> > 6. MMU notifiers supported.
> > 7. FP lazy save/restore supported.
> > 8. SBI v0.1 emulation for KVM Guest available.
> >
> > More feature additions and enhancments will follow after this series and
> > eventually KVM RISC-V will be at-par with other architectures.
>
> This looks clean and it shouldn't take long to have it merged.  Please
> sort out the MAINTAINERS additions.  It would also be nice if
> tools/testing/selftests/kvm/ worked with RISC-V from the beginning;
> there have been recent ARM and s390 ports that you can take some
> inspiration from.

Thanks Paolo.

We will certainly include a patch in v2 series for MAINTAINERS entry.

We referred existing implementation of KVM ARM/ARM64, KVM powerpc
and KVM mips when we started KVM RISC-V port.

Here's a brief TODO list which we want to immediately work upon after this
series:
1. Handle trap from unpriv access in SBI v0.1 emulation
2. In-kernel PLIC emulation
3. SBI v0.2 emulation in-kernel
4. SBI v0.2 hart hotplug emulation in-kernel
5. ..... and so on .....

We will include above TODO list in v2 series cover letter as well.

Apart from above, we also have a more exhaustive TODO list based on study
of other KVM ports which we want to discuss at upcoming LPC 2019.

We were thinking to keep KVM RISC-V disabled by default (i.e. keep it
experimental) until we have validated it on some FPGA or real HW. For now,
users can explicitly enable it and play-around on QEMU emulation. I hope
this is fine with most people ?

Regards,
Anup