linux-kernel - Re: [PATCH v5 00/20] KVM RISC-V Support

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Message-ID: <5a9ccf5f-ee75-9289-814e-0c8b9b3c3f00@amazon.com>
Date:   Fri, 23 Aug 2019 14:28:07 +0200
From:   Alexander Graf <graf@...zon.com>
To:     Anup Patel <anup@...infault.org>,
        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: [PATCH v5 00/20] KVM RISC-V Support



On 23.08.19 14:19, Anup Patel wrote:
> On Fri, Aug 23, 2019 at 5:40 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
>>
>> On 23/08/19 13:44, Graf (AWS), Alexander wrote:
>>>> Overall, I'm quite happy with the code. It's a very clean implementation
>>>> of a KVM target.
>>
>> Yup, I said the same even for v1 (I prefer recursive implementation of
>> page table walking but that's all I can say).
>>
>>>> I will send v6 next week. I will try my best to implement unpriv
>>>> trap handling in v6 itself.
>>> Are you sure unpriv is the only exception that can hit there? What
>>> about NMIs? Do you have #MCs yet (ECC errors)? Do you have something
>>> like ARM's #SError which can asynchronously hit at any time because
>>> of external bus (PCI) errors?
>>
>> As far as I know, all interrupts on RISC-V are disabled by
>> local_irq_disable()/local_irq_enable().
> 
> Yes, we don't have per-CPU interrupts for async bus errors or
> non-maskable interrupts. The local_irq_disable() and local_irq_enable()
> affect all interrupts (excepts traps).

Awesome, so that means you really only need to worry about traps. Even 
easier then! :)

Also, you want to look out for a future extension that adds any of the 
above (NMI, MCE, SError on local bus), as that would then break the 
function ;)


Alex