All of lore.kernel.org
 help / color / mirror / Atom feed
From: Lin Ming <mlin@ss.pku.edu.cn>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: 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>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall
Date: Fri, 20 Apr 2012 23:39:24 +0800	[thread overview]
Message-ID: <1334936364.2863.24.camel@hp6530s> (raw)
In-Reply-To: <1334934367.28331.99.camel@zakaz.uk.xensource.com>

On Fri, 2012-04-20 at 16:06 +0100, Ian Campbell wrote:
> On Fri, 2012-04-20 at 15:50 +0100, Lin Ming wrote:
> > On Fri, Apr 20, 2012 at 9:12 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> > > On Fri, 2012-04-20 at 13:53 +0100, Andrew Cooper wrote:
> > >> >
> > >> > Under what circumstances can these hypercalls fail? Would a BUG_ON be
> > >> > appropriate/
> > >>
> > >> -EFAULT, -EPERM, anything xsm_apic() could return (which looks only to
> > >> be -EPERM).
> > >
> > > So either the guest has called a hypercall which it is not permitted to
> > > or it has called it with invalid parameters of one sort or another. Both
> > > of these would be a code bug in the guest and therefore asserting that
> > > no failure occurred is reasonable?
> > >
> > > What could the caller do with the error other than log it and collapse?
> > >
> > >> The call into Xen itself will return 0 as a value if an
> > >> invalid physbase is passed in the hypercall.

Just checked ioapic_guest_read.
It will return -EINVAL if an invalid physbase is passed in.

> > >
> > >> So a BUG_ON() is not safe/sensible for domU.
> > >
> > > I think you have successfully argued that it is ;-)
> > 
> > BUG_ON is too severe.
> 
> Why? Under what circumstances can this be correctly called in a way
> which would result in the hypercall failing?

Is BUG_ON() reasonable if invalid physbase passed in?

> 
> >  How about WARN_ON?
> > 
> > ret = hypercall(...)
> > 
> > if (ret) {
> >    WARN_ON(1);
> >    return -1;
> > }
> > 
> > 
> > >
> > > Ian.
> 
> 



  reply	other threads:[~2012-04-20 15:40 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1334936364.2863.24.camel@hp6530s \
    --to=mlin@ss.pku.edu.cn \
    --cc=Andrew.Cooper3@citrix.com \
    --cc=Ian.Campbell@citrix.com \
    --cc=konrad.wilk@oracle.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=xen-devel@lists.xensource.com \
    --subject='Re: [Xen-devel] [PATCH] xen/apic: implement io apic read with hypercall' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.