Re: [PATCH v3 15/16] iommu: introduce page response function

From: Alex Williamson <alex.williamson@redhat.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rafael Wysocki <rafael.j.wysocki@intel.com>,
	Lan Tianyu <tianyu.lan@intel.com>,
	Jean Delvare <khali@linux-fr.org>,
	Will Deacon <Will.Deacon@arm.com>,
	"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>
Subject: Re: [PATCH v3 15/16] iommu: introduce page response function
Date: Fri, 8 Dec 2017 16:01:52 -0700	[thread overview]
Message-ID: <20171208160152.738b2ebd@t450s.home> (raw)
In-Reply-To: <20171208124017.519120c1@jacob-builder>

On Fri, 8 Dec 2017 12:40:17 -0800
Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> On Fri, 8 Dec 2017 13:52:00 +0000
> Jean-Philippe Brucker <jean-philippe.brucker@arm.com> wrote:
> 
> > On 07/12/17 21:51, Alex Williamson wrote:  
> > >> Agree, IOMMU driver cannot enforce it. I think VFIO layer can make
> > >> sure page response come from the assigned device and its
> > >> guest/container.    
> > > 
> > > Can we enforce it via the IOMMU/VFIO interface?  If the response is
> > > for a struct device, and not an rid/did embedded in a structure,
> > > then vfio can pass it through w/o worrying about it, ie. response
> > > comes in via ioctl with association to vfio device fd -> struct
> > > vfio_device -> struct device, iommu driver fills in rid/did.
> > > Thanks,    
> > 
> > Yes that's probably the best way, reporting faults and receiving
> > responses on the device fd.
> >   
> Just to put these ideas in to code. The IOMMU API used by VFIO has
> struct device* (derived from fd), no did/rid (to be derived from
> struct device by IOMMU driver.)
> 
> int intel_iommu_page_response(struct iommu_domain *domain, struct device *dev,
> 			struct page_response_msg *msg)
> 
> IOMMU driver can further sanitize by checking whether this is a pending
> page request for the device, and refcount outstanding PRQs.
> 
> Does it sound right?

Yep.  Thanks,

Alex

> /**
>  * Generic page response information based on PCI ATS and PASID spec.
>  * @addr: servicing page address
>  * @pasid: contains process address space ID, used in shared virtual
> memory(SVM)
>  * @resp_code: response code
>  * @page_req_group_id: page request group index
>  * @type: group or stream/single page response
>  * @private_data: uniquely identify device-specific private data for an
>  *                individual page response
> 
>  */
> struct page_response_msg {
> 	u64 addr;
> 	u32 pasid;
> 	u32 resp_code:4;
> #define IOMMU_PAGE_RESP_SUCCESS	0
> #define IOMMU_PAGE_RESP_INVALID	1
> #define IOMMU_PAGE_RESP_FAILURE	0xF
> 
> 	u32 pasid_present:1;
> 	u32 page_req_group_id : 9;
> 	enum page_response_type type;
> 	u32 private_data;
> };