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

[Liu, Yi L]

Hi,

> From: Lu Baolu [mailto:baolu.lu@xxxxxxxxxxxxxxx]
> Sent: Friday, November 9, 2018 9:40 AM
> 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@xxxxxxxxxxxxxxx]
> >> 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@xxxxxxxxxxxxxxx]
> >>>> 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@xxxxxxxxxxxxxxx]
> >>>>>> 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@xxxxxxxxxxxxxxx]
> >>>>>>>> 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 donât 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.

yeah, that would be helpful. :-)

Regards,
Yi Liu