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Re: [Qemu-ppc] [PATCH] spapr/xive: H_INT_ESB is used for LSIs only
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PATCH] spapr/xive: H_INT_ESB is used for LSIs only |
Date: |
Mon, 1 Jul 2019 17:56:45 +1000 |
User-agent: |
Mutt/1.12.0 (2019-05-25) |
On Mon, Jul 01, 2019 at 07:55:03AM +0200, Cédric Le Goater wrote:
> On 01/07/2019 07:07, David Gibson wrote:
> > On Fri, Jun 21, 2019 at 05:05:45PM +0200, Cédric Le Goater wrote:
> >> On 21/06/2019 16:52, Greg Kurz wrote:
> >>> As indicated in the function header, this "hcall is only supported for
> >>> LISNs that have the ESB hcall flag set to 1 when returned from hcall()
> >>> H_INT_GET_SOURCE_INFO". We only set that flag for LSIs actually.
> >>>
> >>> Check that in h_int_esb().
> >>
> >> Indeed. H_INT_ESB should work on any IRQ, but I think it's better
> >> to check that the HCALL is only used with the IRQ requiring it.
> >
> > I'm not so convinced. It seems to me that specifically limiting this
> > to certain things limits our options if we ever need future
> > workarounds for problems with ESB mapping.
> >
> > In addition using H_INT_ESB for non-LSIs could be useful for minimal
> > guests (e.g. kvm-unit-tests) where mapping memory might be awkward.
>
> Ah yes. This is true. There is no real reason for enforcing this
> restriction in QEMU as H_INT_ESB should work on any irq. We can
> keep it that way I guess. It would be a small deviation from PAPR.
True, but "unexpectedly working" is a form of variation exceedingly
unlikely to break anything.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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