Re: [PATCH v2 17/19] iommu/arm-smmu-v3: Add arm_smmu_viommu_cache_invalidate
From: Jason Gunthorpe <jgg@nvidia.com>
Date: 2024-09-14 14:51:03
Also in:
linux-iommu, linux-kselftest, lkml
On Fri, Sep 13, 2024 at 02:33:59AM +0000, Tian, Kevin wrote:
quoted
From: Jason Gunthorpe <jgg@nvidia.com> Sent: Thursday, September 12, 2024 7:08 AM On Wed, Sep 11, 2024 at 08:13:01AM +0000, Tian, Kevin wrote:quoted
Probably there is a good reason e.g. for simplification or better aligned with hw accel stuff. But it's not explained clearly so far.Probably the most concrete thing is if you have a direct assignment invalidation queue (ie DMA'd directly by HW) then it only applies to a single pIOMMU and invalidation commands placed there are unavoidably limited in scope. This creates a representation problem, if we have a vIOMMU that spans many pIOMMUs but invalidations do some subset how to do we model that. Just saying the vIOMMU is linked to the pIOMMU solves this nicely.yes that is a good reason. btw do we expect the VMM to try-and-fail when deciding whether a new vIOMMU object is required when creating a new vdev?
I think there was some suggestion the getinfo could return this, but also I think qemu needs to have a command line that matches physical so maybe it needs some sysfs? Jason