Implement support for get_msi_address_space() callback and return the
IOMMU address space if the device has S1 translation enabled by Guest.
Otherwise return system address space.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
---
 hw/arm/smmuv3-accel.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
index 0573ae3772..395c8175da 100644
--- a/hw/arm/smmuv3-accel.c
+++ b/hw/arm/smmuv3-accel.c
@@ -384,6 +384,26 @@ static void smmuv3_accel_unset_iommu_device(PCIBus *bus, void *opaque,
     }
 }
 
+static AddressSpace *smmuv3_accel_get_msi_as(PCIBus *bus, void *opaque,
+                                             int devfn)
+{
+    SMMUState *bs = opaque;
+    SMMUPciBus *sbus = smmu_get_sbus(bs, bus);
+    SMMUv3AccelDevice *accel_dev = smmuv3_accel_get_dev(bs, sbus, bus, devfn);
+    SMMUDevice *sdev = &accel_dev->sdev;
+
+    /*
+     * If the assigned vfio-pci dev has S1 translation enabled by Guest,
+     * return IOMMU address space for MSI translation. Otherwise, return
+     * system address space.
+     */
+    if (accel_dev->s1_hwpt) {
+        return &sdev->as;
+    } else {
+        return &address_space_memory;
+    }
+}
+
 static bool smmuv3_accel_pdev_allowed(PCIDevice *pdev, bool *vfio_pci)
 {
 
@@ -477,6 +497,7 @@ static const PCIIOMMUOps smmuv3_accel_ops = {
     .get_viommu_flags = smmuv3_accel_get_viommu_flags,
     .set_iommu_device = smmuv3_accel_set_iommu_device,
     .unset_iommu_device = smmuv3_accel_unset_iommu_device,
+    .get_msi_address_space = smmuv3_accel_get_msi_as,
 };
 
 
-- 
2.43.0

On Fri, Oct 31, 2025 at 10:49:49AM +0000, Shameer Kolothum wrote:
> +static AddressSpace *smmuv3_accel_get_msi_as(PCIBus *bus, void *opaque,
> +                                             int devfn)
> +{
> +    SMMUState *bs = opaque;
> +    SMMUPciBus *sbus = smmu_get_sbus(bs, bus);
> +    SMMUv3AccelDevice *accel_dev = smmuv3_accel_get_dev(bs, sbus, bus, devfn);
> +    SMMUDevice *sdev = &accel_dev->sdev;
> +
> +    /*
> +     * If the assigned vfio-pci dev has S1 translation enabled by Guest,
> +     * return IOMMU address space for MSI translation. Otherwise, return
> +     * system address space.
> +     */
> +    if (accel_dev->s1_hwpt) {
> +        return &sdev->as;
> +    } else {
> +        return &address_space_memory;

Should we use the global shared_as? Or is this on purpose to align
with the "&address_space_memory" in kvm_arch_fixup_msi_route()?

Nicolin

> -----Original Message-----
> From: Nicolin Chen <nicolinc@nvidia.com>
> Sent: 31 October 2025 23:58
> To: Shameer Kolothum <skolothumtho@nvidia.com>
> Cc: qemu-arm@nongnu.org; qemu-devel@nongnu.org;
> eric.auger@redhat.com; peter.maydell@linaro.org; Jason Gunthorpe
> <jgg@nvidia.com>; ddutile@redhat.com; berrange@redhat.com; Nathan
> Chen <nathanc@nvidia.com>; Matt Ochs <mochs@nvidia.com>;
> smostafa@google.com; wangzhou1@hisilicon.com;
> jiangkunkun@huawei.com; jonathan.cameron@huawei.com;
> zhangfei.gao@linaro.org; zhenzhong.duan@intel.com; yi.l.liu@intel.com;
> Krishnakant Jaju <kjaju@nvidia.com>
> Subject: Re: [PATCH v5 16/32] hw/arm/smmuv3-accel: Make use of
> get_msi_address_space() callback
> 
> On Fri, Oct 31, 2025 at 10:49:49AM +0000, Shameer Kolothum wrote:
> > +static AddressSpace *smmuv3_accel_get_msi_as(PCIBus *bus, void
> *opaque,
> > +                                             int devfn)
> > +{
> > +    SMMUState *bs = opaque;
> > +    SMMUPciBus *sbus = smmu_get_sbus(bs, bus);
> > +    SMMUv3AccelDevice *accel_dev = smmuv3_accel_get_dev(bs, sbus, bus,
> devfn);
> > +    SMMUDevice *sdev = &accel_dev->sdev;
> > +
> > +    /*
> > +     * If the assigned vfio-pci dev has S1 translation enabled by Guest,
> > +     * return IOMMU address space for MSI translation. Otherwise, return
> > +     * system address space.
> > +     */
> > +    if (accel_dev->s1_hwpt) {
> > +        return &sdev->as;
> > +    } else {
> > +        return &address_space_memory;
> 
> Should we use the global shared_as? Or is this on purpose to align
> with the "&address_space_memory" in kvm_arch_fixup_msi_route()?

Yes, that's on purpose.

Another way to handle is, if  "address_space_memory" is complete no-no, 
to return NULL here and handle it in pci_device_iommu_msi_address_space().

I like the current approach. Possibly can update the doc for get_msi_address_space()
In previous patch to make it clear that "&address_space_memory" should be 
returned if no msi translation is required.

Thanks,
Shameer

On Mon, Nov 03, 2025 at 07:19:08AM -0800, Shameer Kolothum wrote:
> I like the current approach. Possibly can update the doc for get_msi_address_space()
> In previous patch to make it clear that "&address_space_memory" should be 
> returned if no msi translation is required.

Yea. That'd be clearer.

Nicolin