From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@citrix.com>
Subject: Re: [PATCH v6 07/10] libxc: introduce soft reset for
 HVM domains
Date: Wed, 20 May 2015 16:28:19 +0100
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To: Vitaly Kuznetsov <vkuznets@redhat.com>, Julien Grall <julien.grall@citrix.com>
Cc: Andrew Jones <drjones@redhat.com>, Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Julien Grall <julien.grall@linaro.org>, Ian Jackson <ian.jackson@eu.citrix.com>, Olaf Hering <olaf@aepfle.de>, Tim Deegan <tim@xen.org>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <jbeulich@suse.com>, xen-devel@lists.xenproject.org, Wei Liu <wei.liu2@citrix.com>, Daniel De Graaf <dgdegra@tycho.nsa.gov>
List-Id: xen-devel@lists.xenproject.org

On 20/05/15 16:20, Vitaly Kuznetsov wrote:
> Julien Grall <julien.grall@citrix.com> writes:
> 
>> Hi Vitaly,
>>
>> On 13/05/15 10:49, Vitaly Kuznetsov wrote:
>>> +int xc_domain_soft_reset(xc_interface *xch, uint32_t source_dom,
>>> +                         uint32_t dest_dom, domid_t console_domid,
>>> +                         unsigned long *console_mfn, domid_t store_domid,
>>> +                         unsigned long *store_mfn)
>>> +{
>>> +    xc_dominfo_t old_info, new_info;
>>> +    int rc = 1;
>>> +
>>> +    uint32_t hvm_buf_size = 0;
>>> +    uint64_t nr_trans;
>>> +    uint8_t *hvm_buf = NULL;
>>> +    unsigned long console_pfn, store_pfn, io_pfn, buffio_pfn;
>>> +    uint64_t hvm_params[HVM_NR_PARAMS];
>>> +    xen_pfn_t sharedinfo_pfn;
>>> +
>>> +    DPRINTF("%s: soft reset domid %u -> %u", __func__, source_dom, dest_dom);
>>> +
>>> +    if ( xc_domain_getinfo(xch, source_dom, 1, &old_info) != 1 )
>>> +    {
>>> +        PERROR("Could not get old domain info");
>>> +        return 1;
>>> +    }
>>> +
>>> +    if ( xc_domain_getinfo(xch, dest_dom, 1, &new_info) != 1 )
>>> +    {
>>> +        PERROR("Could not get new domain info");
>>> +        return 1;
>>> +    }
>>
>> xc_domain_getinfo returns the first domain ID used from dest_dom. If
>> dest_dom doesn't exist it may return another domain.
>>
>> Therefore you have to check that the info correspond to the correct domain.
> 
> Oh, thanks, I fixed xc_get_tot_pages() a while ago:
> 
> commit 5dcd0dcb85941bd92336e01ae3f8c44730099c96
> Author: Vitaly Kuznetsov <vkuznets@redhat.com>
> Date:   Tue Dec 2 16:18:08 2014 +0100
> 
>     libxc: check in xc_get_tot_pages() that the proper domain is
>     reported
> 
> but I already managed to forget that xc_domain_getinfo() needs
> additional check. Its interface is a bit misleading :-(

Agreed. There is multiple place in libxc and other xen related software
where this function is misused.

It would be worth to introduce a new xc function to return an error if
it's not possible to return the info of the specified domid.

Regards,

-- 
Julien Grall