Re: [Qemu-devel] [PATCH 0/3]: QMP: Introduce inject-nmi command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 26 May 2011 22:23:10 +0300
Blue Swirl <blauwirbel@gmail.com> wrote:

> On Thu, May 26, 2011 at 8:25 PM, Markus Armbruster <armbru@redhat.com> wrote:
> > Luiz Capitulino <lcapitulino@redhat.com> writes:
> >
> >> On Fri, 6 May 2011 18:36:31 +0300
> >> Blue Swirl <blauwirbel@gmail.com> wrote:
> >>
> >>> On Fri, May 6, 2011 at 12:08 PM, Markus Armbruster <armbru@redhat.com> wrote:
> >>> > Blue Swirl <blauwirbel@gmail.com> writes:
> >>> >
> >>> >> On Mon, May 2, 2011 at 6:57 PM, Luiz Capitulino <lcapitulino@redhat.com> wrote:
> >>> >>> On Sat, 30 Apr 2011 09:33:15 +0300
> >>> >>> Blue Swirl <blauwirbel@gmail.com> wrote:
> >>> >>>
> >>> >>>> On Sat, Apr 30, 2011 at 1:40 AM, Luiz Capitulino <lcapitulino@redhat.com> wrote:
> >>> >>>> > This series introduces the inject-nmi command for QMP, which sends an
> >>> >>>> > NMI to _all_ guest's CPUs.
> >>> >>>> >
> >>> >>>> > Also note that this series changes the human monitor nmi command to use
> >>> >>>> > the QMP implementation, which means that it now has a DIFFERENT behavior.
> >>> >>>> > Please, check patch 3/3 for details.
> >>> >>>>
> >>> >>>> As discussed earlier, please change the QMP version for future
> >>> >>>> expandability so that instead of single command 'inject-nmi', 'inject'
> >>> >>>> takes parameter 'nmi'. HMP command 'nmi' can remain for now, but
> >>> >>>> 'inject' should be added.
> >>> >>>
> >>> >>> I'm not sure I agree with this, because we risky overloading 'inject' the
> >>> >>> same way we did with the 'change' command.
> >>> >>>
> >>> >>> What's 'inject' supposed to do in the future?
> >>> >>
> >>> >> Inject other IRQs, for example inject nmi could become an alias to
> >>> >> something like
> >>> >> inject /apic@fee00000:l1int
> >>> >> which would be a shorthand for
> >>> >> raise /apic@fee00000:l1int
> >>> >> lower /apic@fee00000:l1int
> >>> >>
> >>> >> I think we only need a registration framework for IRQs and other signals.
> >>> >
> >>> > Yes, we could use nicer infrastructure for modeling IRQs.  No, we
> >>> > shouldn't reject Lai's work because it doesn't get us there.  Perfect is
> >>> > the enemy of good.
> >>> >
> >>> > Pick one:
> >>> >
> >>> > 1. We take inject-nmi now.  Should we get a more general inject command
> >>> > like the one you envisage later, we can deprecate inject-nmi, and remove
> >>> > it after a suitable grace time.  Big deal.  We get the special problem
> >>> > solved now, without really compromising future solutions for the general
> >>> > problem.
> >>> >
> >>> > 2. We reject inject-nmi now.  The itch Lai tries to scratch remains
> >>> > unscratched until we get a more general inject command.
> >>> >
> >>> > 2a. Rejection "motivates" Lai to solve the general problem[*].  Or maybe
> >>> > it motivates somebody else.  We get the general problem solved sooner.
> >>> > And maybe I get a pony for my birthday, too.
> >>> >
> >>> > 2b. The general problem remains unsolved along with the special problem.
> >>> > We get nothing.
> >>>
> >>> 2c. Don't add full generic IRQ registration and aliases just now but
> >>> handle 'inject' with only 'nmi'. That way we introduce no legacy
> >>> baggage to the syntax.
> >>
> >> Can you give an example on how this is supposed to look like?
> >
> > No reply.  When you demand a redesign to generalize a simple feature to
> > something only you envisage, please explain what exactly you want.
> > Documentation to stick into qmp-commands.hx would be a start.  Here's
> > the baseline from Luiz, for your editing convenience.
> >
> >
> > inject-nmi
> > ----------
> >
> > Inject an NMI on guest's CPUs.
> >
> > Arguments: None.
> >
> > Example:
> >
> > -> { "execute": "inject-nmi" }
> > <- { "return": {} }
> >
> > Note: inject-nmi is only supported for x86 guest currently, it will
> >      returns "Unsupported" error for non-x86 guest.
> 
> I think I explained it many times, but let's try again.
> 
> inject
> ----------
> 
> Inject a signal on guest machine.
> 
> Arguments: signal name.
> 
> Example:
> 
> -> { "execute": "inject",
> "arguments": { "signal": "nmi" } }
> <- { "return": {} }
> 
> -> { "execute": "inject",
> "arguments": { "signal": "/apic@fee00000:l1int" } }
> <- { "return": {} }

Shouldn't this be broken into device and signal (or pin) arguments?

> Note: the set of signals supported depends on the CPU architecture and
> board type, unknown or unsupported names will
>      return "Unsupported" error.

Unsuported error != bad usage error.