linux-kernel - Re: [PATCH v4 04/12] iommu/vt-d: Add 256-bit invalidation descriptor support

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Message-ID: <af077cad-d99b-1cd8-046b-4dbfae3d32f9@linux.intel.com>
Date:   Fri, 9 Nov 2018 09:39:57 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>, Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     baolu.lu@...ux.intel.com, "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v4 04/12] iommu/vt-d: Add 256-bit invalidation descriptor
 support

Hi,

On 11/8/18 3:20 PM, Liu, Yi L wrote:
> Hi,
> 
>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>> Sent: Thursday, November 8, 2018 2:14 PM
>>
>> Hi,
>>
>> On 11/8/18 1:45 PM, Liu, Yi L wrote:
>>>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>>>> Sent: Thursday, November 8, 2018 1:25 PM
>>>> Subject: Re: [PATCH v4 04/12] iommu/vt-d: Add 256-bit invalidation
>>>> descriptor support
>>>>
>>>> Hi,
>>>>
>>>> On 11/8/18 11:49 AM, Liu, Yi L wrote:
>>>>> Hi,
>>>>>
>>>>>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>>>>>> Sent: Thursday, November 8, 2018 10:17 AM
>>>>>> Subject: Re: [PATCH v4 04/12] iommu/vt-d: Add 256-bit invalidation
>>>>>> descriptor support
>>>>>>
>>>>>> Hi Yi,
>>>>>>
>>>>>> On 11/7/18 2:07 PM, Liu, Yi L wrote:
>>>>>>> Hi Baolu,
>>>>>>>
>>>>>>>> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
>>>>>>>> Sent: Monday, November 5, 2018 1:32 PM
>>>>>>> [...]
>>>>>>>
>>>>>>>> ---
>>>>>>>>      drivers/iommu/dmar.c                | 83 +++++++++++++++++++----------
>>>>>>>>      drivers/iommu/intel-svm.c           | 76 ++++++++++++++++----------
>>>>>>>>      drivers/iommu/intel_irq_remapping.c |  6 ++-
>>>>>>>>      include/linux/intel-iommu.h         |  9 +++-
>>>>>>>>      4 files changed, 115 insertions(+), 59 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c index
>>>>>>>> d9c748b6f9e4..ec10427b98ac 100644
>>>>>>>> --- a/drivers/iommu/dmar.c
>>>>>>>> +++ b/drivers/iommu/dmar.c
>>>>>>>> @@ -1160,6 +1160,7 @@ static int qi_check_fault(struct
>>>>>>>> intel_iommu *iommu, int
>>>>>>>> index)
>>>>>>>>      	int head, tail;
>>>>>>>>      	struct q_inval *qi = iommu->qi;
>>>>>>>>      	int wait_index = (index + 1) % QI_LENGTH;
>>>>>>>> +	int shift = qi_shift(iommu);
>>>>>>>>
>>>>>>>>      	if (qi->desc_status[wait_index] == QI_ABORT)
>>>>>>>>      		return -EAGAIN;
>>>>>>>> @@ -1173,13 +1174,15 @@ static int qi_check_fault(struct
>>>>>>>> intel_iommu *iommu, int index)
>>>>>>>>      	 */
>>>>>>>>      	if (fault & DMA_FSTS_IQE) {
>>>>>>>>      		head = readl(iommu->reg + DMAR_IQH_REG);
>>>>>>>> -		if ((head >> DMAR_IQ_SHIFT) == index) {
>>>>>>>> +		if ((head >> shift) == index) {
>>>>>>>> +			struct qi_desc *desc = qi->desc + head;
>>>>>>>> +
>>>>>>>>      			pr_err("VT-d detected invalid descriptor: "
>>>>>>>>      				"low=%llx, high=%llx\n",
>>>>>>>> -				(unsigned long long)qi->desc[index].low,
>>>>>>>> -				(unsigned long long)qi->desc[index].high);
>>>>>>>> -			memcpy(&qi->desc[index], &qi->desc[wait_index],
>>>>>>>> -					sizeof(struct qi_desc));
>>>>>>>> +				(unsigned long long)desc->qw0,
>>>>>>>> +				(unsigned long long)desc->qw1);
>>>>>>> Still missing qw2 and qw3. May make the print differ based on if smts is
>> configed.
>>>>>> qw2 and qw3 are reserved from software point of view. We don't need
>>>>>> to print it for information.
>>>>> But for Scalable mode, it should be valid?
>>>> No. It's reserved for software.
>>> No, I don’t think so. PRQ response would also be queued to hardware by
>>> QI. For such QI descriptors, the high bits are not reserved.
>>>
>>
>> Do you mean the private data fields of a page request descriptor or a page group
>> response descriptor? Those fields contains software defined private data (might a
>> kernel pointer?). We should avoid leaking such information in the generic kernel
>> message for security consideration.
>> Or anything I missed?
> 
> yes, I'm not sure what kind of data it may be in the private data field. From software
> point of view, it may be helpful to show the full content of the QI descriptor for error
> triage. Personally, I'm fine if you keep it on this point.
> 

Okay, thanks.

I think I need to put some comments there so that people could
understand my consideration.

Best regards,
Lu Baolu