On Fri, Apr 11, 2025 at 08:40:54AM -0700, Matthew R. Ochs via Devel wrote:
> Resending: Series has been re-based over latest upstream.
>
> This patch series adds support for configuring the PCI high memory MMIO
> window size for aarch64 virt machine types. This feature has been merged
> into the QEMU upstream master branch [1] and will be available in QEMU 10.0.
> It allows users to configure the size of the high memory MMIO window above
> 4GB, which is particularly useful for systems with large amounts of PCI
> memory requirements.
>
> The feature is exposed through the domain XML as a new PCI feature:
> <features>
> <pci>
> <highmem-mmio-size unit='G'>512</highmem-mmio-size>
> </pci>
> </features>
As a schema design comment. IIUC, the MMIO size we're configuring
is conceptually a characteristic associated with the PCI(e) host
and the memory layout it defines for PCI(e) devices to use.
Checking through our schema I find we already have support
for
<controller type='pci' index='0' model='pci-root'>
<pcihole64 unit='KiB'>1048576</pcihole64>
</controller>
this makes me think that we should model this new attribute
in a similar way, eg so we can support:
<controller type='pci' index='0' model='pci-root'>
<pcihole64 unit='KiB'>1048576</pcihole64>
<pcimmio64 unit='TiB'>2</pcimmio64>
</controller>
(pci-root or pcie-root are interchangable).
This 'pcimmio64' value can then be mapped to whatever hypervisor
or architecture specific setting is appropriate, avoiding exposing
the QEMU arm 'highmem-mmio-size' naming convention.
With regards,
Daniel
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