linux-kernel - Re: [PATCH v2 08/22] iommufd: Abstract iopt_pin_pages and iopt_unpin

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Message-ID: <aBsNhsVryZs2c+AT@nvidia.com>
Date: Wed, 7 May 2025 00:36:38 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
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Subject: Re: [PATCH v2 08/22] iommufd: Abstract iopt_pin_pages and
 iopt_unpin_pages helpers

On Wed, May 07, 2025 at 07:22:24AM +0000, Tian, Kevin wrote:
> > > any reason why this cannot be done by the core? all types of vcmd
> > > queues need to pin the guest buffer pages, no matter the IOMMU
> > > accesses GPA or HPA.

> > But I am doing in the core. I have iopt_pin_pages() called in the
> > core ioctl handler iommufd_vqueue_alloc_ioctl():
 
> IMHO we just want to keep the pin logic in the core while leaving
> the check of PFN continuity to the driver (or have a way for the 
> driver to communicate such need to the core). 
> 
> It's possible for have an implementation with IOMMU accessing 
> GPA of the queue which further goes through the stage-2 
> translation. In such case it's fine to have disjointed PFNs.

That makes sense. In the iommufd_viommu_ops structure, we can add
"u32 flag" where driver can define IOMMUFD_VQUEUE_CONTIGUOUS_PFNS?

Thanks
Nicolin