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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Lin Ming <mlin@ss.pku.edu.cn>
Cc: Ian Campbell <Ian.Campbell@citrix.com>,
	Andrew Cooper <Andrew.Cooper3@citrix.com>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall
Date: Mon, 23 Apr 2012 11:11:23 -0400	[thread overview]
Message-ID: <20120423151123.GC24481@phenom.dumpdata.com> (raw)
In-Reply-To: <CAF1ivSamaYzQDwjFqRGrnQ+fCr0D4vLGuG4JRBZ3_GD_y8yY=A@mail.gmail.com>

> >> > How about return -1 on error?
> >> > The calling function can check -1 for error.
> >>
> >> Isn't -1 potentially (at least theoretically) a valid value to read from
> >> one of these registers?
> >
> > Yeah, but then we are back to crashing at bootup (with dom0) :-)
> >
> > Perhaps the fallback is to emulate (so retain some of the original code)
> > as we have been since .. uh 3.0?
> 
> Do you mean the return value of io_apic_read in 3.0?

No. I meant that we would continue to emulate. The improvement
is that now we do:

      if (reg == 0x1)
              return 0x00170020;
      else if (reg == 0x0)
              return apic << 24;

instead of 0xfdfdfdfd.

> It's 0xffffffff.

Now it is 0xfdfdfdfd.

I am suggesting that instead of BUG_ON(), we fallback to do returning
an emulatated IO_APIC values - like the ones that this original patch
cooked up..

  reply	other threads:[~2012-04-23 15:16 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-20  9:25 Lin Ming
2012-04-20  9:58 ` [Xen-devel] " Andrew Cooper
2012-04-20 11:13   ` Lin Ming
2012-04-20 12:38     ` Ian Campbell
2012-04-20 12:52       ` Jan Beulich
2012-04-20 12:53       ` Andrew Cooper
2012-04-20 13:12         ` Ian Campbell
2012-04-20 13:20           ` Andrew Cooper
2012-04-20 14:50           ` Lin Ming
2012-04-20 14:50             ` Lin Ming
2012-04-20 14:59             ` [Xen-devel] " Jan Beulich
2012-04-20 15:06             ` Ian Campbell
2012-04-20 15:39               ` Lin Ming
2012-04-20 16:43                 ` Konrad Rzeszutek Wilk
2012-04-20 16:41       ` Konrad Rzeszutek Wilk
2012-04-23  8:42         ` Lin Ming
2012-04-23 15:11           ` Konrad Rzeszutek Wilk [this message]
2012-04-24 14:43             ` Lin Ming
2012-04-24 16:23               ` Konrad Rzeszutek Wilk
2012-04-25 10:06                 ` Lin Ming
2012-04-26 15:33                   ` Konrad Rzeszutek Wilk
2012-04-26 15:33                     ` Konrad Rzeszutek Wilk

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