> -----Original Message-----
> From: Jason Gunthorpe <[email protected]>
> Sent: 05 November 2025 18:11
> To: Eric Auger <[email protected]>
> Cc: Shameer Kolothum <[email protected]>; qemu-
> [email protected]; [email protected]; [email protected];
> Nicolin Chen <[email protected]>; [email protected];
> [email protected]; Nathan Chen <[email protected]>; Matt Ochs
> <[email protected]>; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> Krishnakant Jaju <[email protected]>
> Subject: Re: [PATCH v5 15/32] hw/pci/pci: Introduce optional
> get_msi_address_space() callback
>
> On Wed, Nov 05, 2025 at 06:25:05PM +0100, Eric Auger wrote:
> > if the guest doorbell address is wrong because not properly translated,
> > vgic_msi_to_its() will fail to identify the ITS to inject the MSI in.
> > See kernel kvm/vgic/vgic-its.c vgic_msi_to_its and
> > vgic_its_inject_msi
>
> Which has been exactly my point to Nicolin. There is no way to
> "properly translate" the vMSI address in a HW accelerated SMMU
> emulation.
>
> The vMSI address must only be used for some future non-RMR HW only
> path.
>
> To keep this flow working qemu must ignore the IOVA from the guest and
> always replace it with its own idea of what the correct ITS address is
> for KVM to work. It means we don't correctly emulate guest
> misconfiguration of the MSI address.
>
> Thus it should never be "translated" in this configuration, that's a
> broken idea when working with the HW accelerated vSMMU.
Ah.. I get it now. You are not questioning the flow here but the
"translate" part. Agree it is not safe to use smmuv3_translate()
in an HW accelerated case. We need somehow to hook into this
path and provide a correct ITS address for KVM.
Hmm.... need to see how to do that in the least invasive way.
Thanks,
Shameer
