Re: [RFC PATCH v3 14/15] Read and validate host SMMUv3 feature bits

[Nicolin Chen via <qemu-devel@nongnu.org>]

On Mon, Jul 14, 2025 at 01:04:02PM -0700, Nicolin Chen wrote:
> On Mon, Jul 14, 2025 at 04:59:40PM +0100, Shameer Kolothum wrote:
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > 
> > Not all fields in the SMMU IDR registers are meaningful for userspace.
> > Only the following fields can be used:
> > 
> >   - IDR0: ST_LEVEL, TERM_MODEL, STALL_MODEL, TTENDIAN, CD2L, ASID16, TTF  
> >   - IDR1: SIDSIZE, SSIDSIZE  
> >   - IDR3: BBML, RIL  
> >   - IDR5: VAX, GRAN64K, GRAN16K, GRAN4K
> > 
> > Use the relevant fields from these to check whether the host and emulated
> > SMMUv3 features are sufficiently aligned to enable accelerated SMMUv3
> > support.
> > 
> > To retrieve this information from the host, at least one vfio-pci device
> > must be assigned with "arm-smmuv3,accel=on" usage. Add a check to enforce
> > this.
> > 
> > Note:
> > 
> > ATS, PASID, and PRI features are currently not supported. Only devices
> > that do not require or make use of these features are expected to work.
> 
> Can we support ATS/PASID at least? I need to double check intel's
> series, but I somehow recall that there is a PASID cap support in
> the VFIO level, so VM could actually report ATS/PASID caps?
> 
> The invalidation part could forward ATC_INV command too, as kernel
> supports that.

Also, the Subject is missing prefix "hw/arm/smmuv3-accel:".

Nicolin