linux-kernel - RE: [PATCH v11 14/16] iommu: Track iopf group instead of last fault

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Message-ID: <BN9PR11MB5276D08766EF06B55F471EDC8C462@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Tue, 6 Feb 2024 08:31:51 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, 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>
CC: "Liu, Yi L" <yi.l.liu@...el.com>, Jacob Pan
	<jacob.jun.pan@...ux.intel.com>, Longfang Liu <liulongfang@...wei.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>, Joel Granados <j.granados@...sung.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>, Jason Gunthorpe <jgg@...dia.com>
Subject: RE: [PATCH v11 14/16] iommu: Track iopf group instead of last fault

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, January 30, 2024 4:09 PM
> 
> Previously, before a group of page faults was passed to the domain's iopf
> handler, the last page fault of the group was kept in the list of
> iommu_fault_param::faults. In the page fault response path, the group's
> last page fault was used to look up the list, and the page faults were
> responded to device only if there was a matched fault.
> 
> The previous approach seems unnecessarily complex and not performance
> friendly. Put the page fault group itself to the outstanding fault list.
> It can be removed in the page fault response path or in the
> iopf_queue_remove_device() path. The pending list is protected by
> iommu_fault_param::lock. To allow checking for the group's presence in
> the list using list_empty(), the iopf group should be removed from the
> list with list_del_init().
> 
> IOMMU_PAGE_RESP_PASID_VALID is set in the code but not used anywhere.
> Remove it to make the code clean. IOMMU_PAGE_RESP_PASID_VALID is set
> in the response message indicating that the response message includes
> a valid PASID value. Actually, we should keep this hardware detail in
> the individual driver. When the page fault handling framework in IOMMU
> and IOMMUFD subsystems includes a valid PASID in the fault message, the
> response message should always contain the same PASID value. Individual
> drivers should be responsible for deciding whether to include the PASID
> in the messages they provide for the hardware.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> Tested-by: Yan Zhao <yan.y.zhao@...el.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>