Date: Tue, 14 Jan 2014 16:49:22 +0000 From: Julien Grall <julien.grall@linaro.org> To: =?UTF-8?B?Um9nZXIgUGF1IE1vbm7DqQ==?= <roger.pau@citrix.com> Cc: jhb@freebsd.org, xen-devel@lists.xen.org, Julien Grall <julien.grall@citrix.com>, freebsd-xen@freebsd.org, freebsd-current@freebsd.org, kib@freebsd.org, gibbs@freebsd.org Subject: Re: [PATCH v10 14/20] xen: introduce xenpv bus and a dummy pvcpu device Message-ID: <52D56A92.4070100@linaro.org> In-Reply-To: <52D563DE.1020207@citrix.com> References: <1389711582-66908-1-git-send-email-roger.pau@citrix.com> <1389711582-66908-15-git-send-email-roger.pau@citrix.com> <52D55AB4.4010504@linaro.org> <52D560EB.8040108@citrix.com> <52D5625D.7030702@citrix.com> <52D563DE.1020207@citrix.com>
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On 01/14/2014 04:20 PM, Roger Pau Monné wrote:
> On 14/01/14 17:14, Julien Grall wrote:
>> On 01/14/2014 04:08 PM, Roger Pau Monné wrote:
>>> On 14/01/14 16:41, Julien Grall wrote:
>>>> On 01/14/2014 02:59 PM, Roger Pau Monne wrote:
>>>>> +static int
>>>>> +xenpv_attach(device_t dev)
>>>>> +{
>>>>> + device_t child;
>>>>> +
>>>>> + if (xen_hvm_domain()) {
>>>>> + device_t xenpci;
>>>>> + devclass_t dc;
>>>>> +
>>>>> + /* Make sure xenpci has been attached */
>>>>> + dc = devclass_find("xenpci");
>>>>> + if (dc == NULL)
>>>>> + panic("unable to find xenpci devclass");
>>>>> +
>>>>> + xenpci = devclass_get_device(dc, 0);
>>>>> + if (xenpci == NULL)
>>>>> + panic("unable to find xenpci device");
>>>>> +
>>>>> + if (!device_is_attached(xenpci))
>>>>> + panic("trying to attach xenpv before xenpci");
>>>>> + }
>>>>
>>>> Can you use the identify method to add the xenpci device?
>>>
>>> I don't think so, xenpci is a pci device, it is detected and plugged by
>>> the pci bus code.
>>
>> Oups, I though you are trying to add the device. In this case, the check
>> seems pointless. In which case the xenpci couldn't exist?
>
> It's just a "belt and suspenders", if we attach the xenpv bus without
> xenpci being attached first a bunch of things are going to fail, I
> though it might be best to print a clear error message about what went
> wrong in order to help debug it.
I only see one place which could failed, and we are already protected.
It's when we are trying to allocate space from grant-table via
xenpci_alloc_space.
I think this error should be enough to understand the problem. At the
same time, it's the same things with xenstore. If grant-table
initialization has failed, an error message is just printed and FreeBSD
will likely failed later when it will try to initialized the PV disk.
--
Julien Grall
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