Subject: Re: [PATCH v4 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices

From: Jason Gunthorpe <[email-masked]>
Date: Wed, 20 May 2026 11:34:10 -0300

On Wed, May 20, 2026 at 09:12:31PM +0800, Yi Liu wrote:
> On 4/27/26 13:54, Nicolin Chen wrote:
> > Controlled by the IOMMU driver, ATS is usually enabled "on demand" when a
> > given PASID on a device is attached to an I/O page table. This is working
> > even when a device has no translation on its RID (i.e., the RID is IOMMU
> > bypassed).
> 
> nit: this description seems not accurate. Intel iommu driver enables ATS
> in the probe_device() phase. mind tweak a bit to avoid misleading
> message. :)

It probably shouldn't do this, it should follow ARM and have it
dynamic during domain attach.

For security we need ATS disabled for blocking domains at a minimum.

Jason