Re: [RESEND][PATCH v1 1/2] xen_arm: Create virtio-mmio devices during initialization

[Stefano Stabellini]

On Thu, 29 Jun 2023, Vikram Garhwal wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> In order to use virtio backends we need to allocate virtio-mmio
> parameters (irq and base) and register corresponding buses.
> 
> Use the constants defined in public header arch-arm.h to be
> aligned with the toolstack. So the number of current supported
> virtio-mmio devices is 10.
> 
> For the interrupts triggering use already existing on Arm
> device-model hypercall.
> 
> The toolstack should then insert the same amount of device nodes
> into guest device-tree.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> ---
>  hw/arm/xen_arm.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/hw/arm/xen_arm.c b/hw/arm/xen_arm.c
> index 60dcd1bcc7..c0a93f2c9d 100644
> --- a/hw/arm/xen_arm.c
> +++ b/hw/arm/xen_arm.c
> @@ -26,6 +26,7 @@
>  #include "qapi/qapi-commands-migration.h"
>  #include "qapi/visitor.h"
>  #include "hw/boards.h"
> +#include "hw/irq.h"
>  #include "hw/sysbus.h"
>  #include "sysemu/block-backend.h"
>  #include "sysemu/tpm_backend.h"
> @@ -59,6 +60,32 @@ struct XenArmState {
>      } cfg;
>  };
>  
> +#define VIRTIO_MMIO_DEV_SIZE   0x200

Is this coming from QEMU? Or is it standard virtio?

Just asking to make sure that we don't run into a virtio device that
needs more than 0x200 of MMIO size.


> +#define NR_VIRTIO_MMIO_DEVICES   \
> +   (GUEST_VIRTIO_MMIO_SPI_LAST - GUEST_VIRTIO_MMIO_SPI_FIRST)
> +
> +static void xen_set_irq(void *opaque, int irq, int level)
> +{
> +    xendevicemodel_set_irq_level(xen_dmod, xen_domid, irq, level);
> +}

Just a note: likely the xendevicemodel_set_irq_level call needs
privileges. Just something to keep in mind for when we try to run QEMU
in a domain other than Dom0. No need to do anything for now.

Everything looks good. If we can be sure 0x200 is the right MMIO size
for virtio devices then I would provide by Ack.


> +static void xen_create_virtio_mmio_devices(XenArmState *xam)
> +{
> +    int i;
> +
> +    for (i = 0; i < NR_VIRTIO_MMIO_DEVICES; i++) {
> +        hwaddr base = GUEST_VIRTIO_MMIO_BASE + i * VIRTIO_MMIO_DEV_SIZE;
> +        qemu_irq irq = qemu_allocate_irq(xen_set_irq, NULL,
> +                                         GUEST_VIRTIO_MMIO_SPI_FIRST + i);
> +
> +        sysbus_create_simple("virtio-mmio", base, irq);
> +
> +        DPRINTF("Created virtio-mmio device %d: irq %d base 0x%lx\n",
> +                i, GUEST_VIRTIO_MMIO_SPI_FIRST + i, base);
> +    }
> +}
> +
>  void arch_handle_ioreq(XenIOState *state, ioreq_t *req)
>  {
>      hw_error("Invalid ioreq type 0x%x\n", req->type);
> @@ -110,6 +137,8 @@ static void xen_arm_init(MachineState *machine)
>  
>      xen_register_ioreq(xam->state, machine->smp.cpus, xen_memory_listener);
>  
> +    xen_create_virtio_mmio_devices(xam);
> +
>  #ifdef CONFIG_TPM
>      if (xam->cfg.tpm_base_addr) {
>          xen_enable_tpm(xam);
> -- 
> 2.25.1
>