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Re: [RFC PATCH 3/3] hw/block/nvme: add nvme_inject_state HMP command
From: |
Minwoo Im |
Subject: |
Re: [RFC PATCH 3/3] hw/block/nvme: add nvme_inject_state HMP command |
Date: |
Thu, 11 Feb 2021 15:06:32 +0900 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
On 21-02-11 13:24:22, Keith Busch wrote:
> On Thu, Feb 11, 2021 at 12:38:48PM +0900, Minwoo Im wrote:
> > On 21-02-11 12:00:11, Keith Busch wrote:
> > > But I would prefer to see advanced retry tied to real errors that can be
> > > retried, like if we got an EBUSY or EAGAIN errno or something like that.
> >
> > I have seen a thread [1] about ACRE. Forgive me If I misunderstood this
> > thread or missed something after this thread. It looks like CRD field in
> > the CQE can be set for any NVMe error state which means it *may* depend on
> > the device status.
>
> Right! Setting CRD values is at the controller's discretion for any
> error status as long as the host enables ACRE.
>
> > And this patch just introduced a internal temporarily error state of
> > the controller by returning Command Intrrupted status.
>
> It's just purely synthetic, though. I was hoping something more natural
> could trigger the status. That might not provide the deterministic
> scenario you're looking for, though.
That makes snese. If some status can be triggered more naturally, that
would be much better.
> I'm not completely against using QEMU as a development/test vehicle for
> corner cases like this, but we are introducing a whole lot of knobs
> recently, and you practically need to be a QEMU developer to even find
> them. We probably should step up the documentation in the wiki along
> with these types of features.
Oh, that's a really good advice, really appreciate that one.
> > I think, in this stage, we can go with some errors in the middle of the
> > AIO (nvme_aio_err()) for advanced retry. Shouldn't AIO errors are
> > retry-able and supposed to be retried ?
>
> Sure, we can assume that receiving an error in the AIO callback means
> the lower layers exhausted available recovery mechanisms.
Okay, please let me find a way to trigger this kind of errors more
naturally. I think this HMP command should be the last one to try if
there's nothing we can do really.
- [RFC PATCH 2/3] hw/block/nvme: support command retry delay, (continued)