From mboxrd@z Thu Jan  1 00:00:00 1970
From: Malcolm Crossley <malcolm.crossley@citrix.com>
Subject: Re: [PATCH v3] IOMMU: Prevent VT-d device IOTLB
 operations on wrong IOMMU
Date: Tue, 17 Jun 2014 17:15:15 +0100
Message-ID: <53A06993.9010608@citrix.com>
References: <0ec71ff08df1f10b1d41.1403015866@malcolmc.uk.xensource.com>
	<53A07589020000780001B253@mail.emea.novell.com>
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To: Jan Beulich <JBeulich@suse.com>
Cc: kevin.tian@intel.com, andrew.cooper3@citrix.com, xen-devel@lists.xen.org, paul.durrant@citrix.com, Aravind.Gopalakrishnan@amd.com, suravee.suthikulpanit@amd.com, yang.z.zhang@intel.com
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On 17/06/14 16:06, Jan Beulich wrote:
>>>> On 17.06.14 at 16:37, <malcolm.crossley@citrix.com> wrote:
>> --- a/xen/drivers/passthrough/vtd/x86/ats.c
>> +++ b/xen/drivers/passthrough/vtd/x86/ats.c
>> @@ -120,6 +120,10 @@ int dev_invalidate_iotlb(struct iommu *i
>>      {
>>          sid = (pdev->bus << 8) | pdev->devfn;
>>  
>> +        /* Only invalidate devices that belong to this IOMMU */
>> +        if ( !pdev->iommu || pdev->iommu != iommu )
>> +            continue;
> 
> I meant to ask before and then forgot: What is the first half of this
> condition good/needed for?
>
Defensive coding to prevent a NULL pointer deference if the Intel or
core ATS code goes wrong.

Malcolm

> Jan
>