> -----Original Message----- > From: Peter Maydell <[email protected]> > Sent: 27 October 2025 11:28 > To: Shameer Kolothum <[email protected]> > Cc: [email protected]; [email protected]; > [email protected]; Nicolin Chen <[email protected]>; > [email protected]; Nathan Chen <[email protected]>; Matt Ochs > <[email protected]>; [email protected] > Subject: Re: [PATCH v2] docs/system/arm/virt: Document user-creatable > SMMUv3 > > External email: Use caution opening links or attachments > > > On Fri, 24 Oct 2025 at 09:46, Shameer Kolothum > <[email protected]> wrote: > > > > The virt machine now supports creating multiple SMMUv3 instances, each > > associated with a separate PCIe root complex. > > > > Update the documentation with an example. > > > > Signed-off-by: Shameer Kolothum <[email protected]> > > Thanks. I have some minor word-smithing tweaks, but I'll just > apply them to this patch in target-arm.next if you're OK with > that: > > > --- a/docs/system/arm/virt.rst > +++ b/docs/system/arm/virt.rst > @@ -224,23 +224,24 @@ SMMU configuration > """""""""""""""""" > > Machine-wide SMMUv3 IOMMU > - See the machine-specific ``iommu`` option above. This allows specifying > - a single, machine-wide SMMUv3 instance that applies to all devices in > - the PCIe topology. > + Setting the machine-specific option ``iommu=smmuv3`` causes QEMU to > + create a single, machine-wide SMMUv3 instance that applies to all > + devices in the PCIe topology. > > For information about selectively bypassing devices, refer to > ``docs/bypass-iommu.txt``. > > User-creatable SMMUv3 devices > - Allows creating multiple user-defined SMMUv3 devices, each associated > - with a separate PCIe root complex. This is only permitted if the > - machine-wide SMMUv3 (``iommu=smmuv3``) option is not used. > + You can use the ``-device arm-smmuv3`` option to create multiple > + user-defined SMMUv3 devices, each associated with a separate PCIe > + root complex. This is only permitted if the machine-wide SMMUv3 > + (``iommu=smmuv3``) option is not used. Each ``arm-smmuv3`` device > + uses the ``primary-bus`` sub-option to specify which PCIe root > + complex it is associated with. > > This model is useful when you want to mirror a host configuration where > each NUMA node typically has its own SMMU, allowing the VM topology to > - align more closely with the host’s hardware layout. Supporting multiple > - SMMUv3 instances is also a prerequisite for future accelerated SMMUv3 > - support. > + align more closely with the host’s hardware layout. > > Example:: > > > > > (I deleted the sentence about SMMU acceleration because that > isn't upstream yet. When it lands then we can update the > docs if the version of it that lands can't support acceleration > of a single machine-wide accelerator.)
Ok. The changes look fine to me. Thanks, Shameer
