From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [RFC PATCH 2/7] iommu: add iommu_lookup_page to
 lookup guest gfn for a particular IOMMU mapping
Date: Wed, 24 Feb 2016 15:10:39 +0000
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To: George Dunlap <George.Dunlap@eu.citrix.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Malcolm Crossley <malcolm.crossley@citrix.com>, Jan Beulich <jbeulich@suse.com>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
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On 24/02/16 15:08, George Dunlap wrote:
> On Wed, Feb 17, 2016 at 8:22 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com> wrote:
>>> +    {
>>> +        *gfn = bfn;
>>> +        return 0;
>>> +    }
>>> +
>>> +    if ( !iommu_enabled || !hd->platform_ops ||
>>> +            !hd->platform_ops->lookup_page )
>>> +        return -ENOMEM;
>> -ENOMEM ? ENXIO ? Or maybe -ENOSYS for the case when hd->platform_ops
>> is not set nor ->lookup_page?
> I think ENOTSUPP, perhaps?  ENOMEM means a memory allocation failed
> (which it hasn't); ENOSYS means this is an invalid system call (which
> it isn't).  ESRCH could be close too, but it seems like that would be
> more appropriate when you try to lookup a non-existent BFN.

Xen (fairly) consistently uses ESRCH for "domain not found".  I would
recommend -ENOTSUPP here.

~Andrew