[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v2 2/4] x86/apic: force phys mode if interrupt remapping is disabled


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Wed, 4 Dec 2019 10:17:34 +0100
  • Authentication-results: esa4.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=roger.pau@xxxxxxxxxx; spf=Pass smtp.mailfrom=roger.pau@xxxxxxxxxx; spf=None smtp.helo=postmaster@xxxxxxxxxxxxxxx
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Wei Liu <wl@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Delivery-date: Wed, 04 Dec 2019 09:17:53 +0000
  • Ironport-sdr: 5OCZPiA+GUgLRDv9JgDl3OtKFIDB+X9e0eVFa5RgRTvEgxt+Y0CKR6wbI1jnZh7dDGG2gFIs1w i4eSRYvsTJkY/Hbb04F3//+vAxbKm9f0bRToAkyT22EjmvfHnV6fEH2Mi1xF2AoiVin3DWoITD 4M7/aPDORWMSyUezj1zy5SkyFpE9b5rrGM1+Ev5pAG63RNWPy+IkNiiRGOC5dJMcllpnVAixaK HXrHckxg1l1euupJKlJsR17NWqC1wXv4Zs/6zfRn+S8dLDyrnI71XaUPYQpci5nakmKvpOZSG5 pUc=
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Tue, Dec 03, 2019 at 04:14:46PM +0100, Jan Beulich wrote:
> On 29.11.2019 12:38, Roger Pau Monné  wrote:
> > On Fri, Nov 29, 2019 at 12:28:49PM +0100, Roger Pau Monne wrote:
> >> Cluster mode can only be used with interrupt remapping support, since
> >> the top 16bits of the APIC ID are filled with the cluster ID, and
> >> hence on systems where the physical ID is still smaller than 255 the
> >> cluster ID is not. Force x2APIC to use physical mode if there's no
> >> interrupt remapping support.
> >>
> >> Note that this requires a further patch in order to enable x2APIC
> >> without interrupt remapping support.
> >>
> >> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > 
> > This is missing a command line doc update and the logic below ignores
> > a user-set x2apic_phys value.
> 
> So what would the behavior be in your opinion when the user
> has requested cluster mode? I can't see you do much other
> than panic()-ing, perhaps it's better to override the request
> (as you already do)?

I think panic'ing is fine, a user shouldn't be setting x2apic_phys
unless they know what are doing, and then Xen changing it on the back
of the user also doesn't seem fine.

A panic explaining that x2apic_phys=false is not supported and that
the box can only be booted with x2apic phys mode should be fine IMO.

Thanks, Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.