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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 22:50:57 +0800	[thread overview]
Message-ID: <CAF1ivSaPshQf=BZ1gKLUq1yRF_MWeyjjVWkfv+E_jT+K5CFmAA@mail.gmail.com> (raw)
In-Reply-To: <1334927566.28331.80.camel@zakaz.uk.xensource.com>

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.
>
>> So a BUG_ON() is not safe/sensible for domU.
>
> I think you have successfully argued that it is ;-)

BUG_ON is too severe. How about WARN_ON?

ret = hypercall(...)

if (ret) {
   WARN_ON(1);
   return -1;
}


>
> Ian.

WARNING: multiple messages have this Message-ID
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: [PATCH] xen/apic: implement io apic read with hypercall
Date: Fri, 20 Apr 2012 22:50:57 +0800	[thread overview]
Message-ID: <CAF1ivSaPshQf=BZ1gKLUq1yRF_MWeyjjVWkfv+E_jT+K5CFmAA@mail.gmail.com> (raw)
In-Reply-To: <1334927566.28331.80.camel@zakaz.uk.xensource.com>

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.
>
>> So a BUG_ON() is not safe/sensible for domU.
>
> I think you have successfully argued that it is ;-)

BUG_ON is too severe. How about WARN_ON?

ret = hypercall(...)

if (ret) {
   WARN_ON(1);
   return -1;
}


>
> Ian.

  parent reply	other threads:[~2012-04-20 15:00 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 [this message]
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
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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