Re: [PATCH v2 06/15] hw/riscv/virt.c: support for RISC-V IOMMU PCIDevice hotplug

[Andrew Jones]

On Wed, May 15, 2024 at 02:25:31PM GMT, Eric Cheng wrote:
> On 3/8/2024 12:03 AM, Daniel Henrique Barboza wrote:
> > From: Tomasz Jeznach <tjeznach@rivosinc.com>
> > 
> > Generate device tree entry for riscv-iommu PCI device, along with
> > mapping all PCI device identifiers to the single IOMMU device instance.
> > 
> > Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
> > Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> > ---
> >   hw/riscv/virt.c | 33 ++++++++++++++++++++++++++++++++-
> >   1 file changed, 32 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> > index a094af97c3..67a8267747 100644
> > --- a/hw/riscv/virt.c
> > +++ b/hw/riscv/virt.c
> > @@ -32,6 +32,7 @@
> >   #include "hw/core/sysbus-fdt.h"
> >   #include "target/riscv/pmu.h"
> >   #include "hw/riscv/riscv_hart.h"
> > +#include "hw/riscv/iommu.h"
> >   #include "hw/riscv/virt.h"
> >   #include "hw/riscv/boot.h"
> >   #include "hw/riscv/numa.h"
> > @@ -1004,6 +1005,30 @@ static void create_fdt_virtio_iommu(RISCVVirtState 
> > *s, uint16_t bdf)
> >                              bdf + 1, iommu_phandle, bdf + 1, 0xffff - bdf);
> >   }
> > +static void create_fdt_iommu(RISCVVirtState *s, uint16_t bdf)
> > +{
> > +    const char comp[] = "riscv,pci-iommu";
> > +    void *fdt = MACHINE(s)->fdt;
> > +    uint32_t iommu_phandle;
> > +    g_autofree char *iommu_node = NULL;
> > +    g_autofree char *pci_node = NULL;
> > +
> > +    pci_node = g_strdup_printf("/soc/pci@%lx",
> > +                               (long) virt_memmap[VIRT_PCIE_ECAM].base);
> > +    iommu_node = g_strdup_printf("%s/iommu@%x", pci_node, bdf);
> > +    iommu_phandle = qemu_fdt_alloc_phandle(fdt);
> > +    qemu_fdt_add_subnode(fdt, iommu_node);
> > +
> > +    qemu_fdt_setprop(fdt, iommu_node, "compatible", comp, sizeof(comp));
> > +    qemu_fdt_setprop_cell(fdt, iommu_node, "#iommu-cells", 1);
> > +    qemu_fdt_setprop_cell(fdt, iommu_node, "phandle", iommu_phandle);
> > +    qemu_fdt_setprop_cells(fdt, iommu_node, "reg",
> > +                           bdf << 8, 0, 0, 0, 0);
> > +    qemu_fdt_setprop_cells(fdt, pci_node, "iommu-map",
> > +                           0, iommu_phandle, 0, bdf,
> > +                           bdf + 1, iommu_phandle, bdf + 1, 0xffff - bdf);
> > +}
> 
> Is it really necessary to add this iommu-pci device in riscv virt machine,
> rather than other 'physical' machine type? virt machine already has its
> virtio-iommu.
>

We need both, just as the Arm virt machine has both. virtio-iommu is for
guests, but the Arm and RISCV virt machines are both also used as hosts.

Thanks,
drew