linux-kernel - RE: [PATCH 9/9] iommu: Use fault cookie to store iopf

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Date:   Thu, 13 Jul 2023 08:01:51 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
CC:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        "Robin Murphy" <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 9/9] iommu: Use fault cookie to store iopf_param

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Thursday, July 13, 2023 11:44 AM
> 
> On 2023/7/13 11:24, Tian, Kevin wrote:
> >> From: Baolu Lu <baolu.lu@...ux.intel.com>
> >> Sent: Wednesday, July 12, 2023 11:13 AM
> >>
> >> On 2023/7/12 6:02, Jacob Pan wrote:
> >>> On Tue, 11 Jul 2023 09:06:42 +0800, Lu Baolu<baolu.lu@...ux.intel.com>
> >>> wrote:
> >>>
> >>>> @@ -158,7 +158,7 @@ int iommu_queue_iopf(struct iommu_fault
> *fault,
> >>>> struct device *dev)
> >>>>    	 * As long as we're holding param->lock, the queue can't be
> >>>> unlinked
> >>>>    	 * from the device and therefore cannot disappear.
> >>>>    	 */
> >>>> -	iopf_param = param->iopf_param;
> >>>> +	iopf_param = iommu_get_device_fault_cookie(dev, 0);
> >>> I am not sure I understand how does it know the cookie type is
> iopf_param
> >>> for PASID 0?
> >>>
> >>> Between IOPF and IOMMUFD use of the cookie, cookie types are
> different,
> >>> right?
> >>>
> >>
> >> The fault cookie is managed by the code that delivers or handles the
> >> faults. The sva and IOMMUFD paths are exclusive.
> >>
> >
> > what about siov? A siov-capable device can support sva and iommufd
> > simultaneously.
> 
> For siov case, the pasid should be global. RID and each pasid are still
> exclusive, so I don't see any problem. Did I overlook anything?
> 

they are exclusive but it's weird to see some pasids (for sva) on this
device are tracked by slot#0 while other pasids (for iommufd) occupies
per-pasid slot.

why not generalizing them given you name it as "per-pasid fault cookie"?