Re: [RESEND][PATCH v1 2/2] xen_arm: Initialize RAM and add hi/low memory regions

[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 initialize RAM for the
> xen-mapcache (which is responsible for mapping guest memory using foreign
> mapping) to work. Calculate and add hi/low memory regions based on
> machine->ram_size.
> 
> Use the constants defined in public header arch-arm.h to be aligned with the 
> xen
> toolstack.
> 
> While using this machine, the toolstack should then pass real ram_size using
> "-m" arg. If "-m" is not given, create a QEMU machine without IOREQ, TPM and
> VIRTIO to keep it usable for /etc/init.d/xencommons.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> ---
>  hw/arm/xen_arm.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/hw/arm/xen_arm.c b/hw/arm/xen_arm.c
> index c0a93f2c9d..cc4dffee70 100644
> --- a/hw/arm/xen_arm.c
> +++ b/hw/arm/xen_arm.c
> @@ -60,6 +60,8 @@ struct XenArmState {
>      } cfg;
>  };
>  
> +static MemoryRegion ram_lo, ram_hi;
> +
>  #define VIRTIO_MMIO_DEV_SIZE   0x200
>  
>  #define NR_VIRTIO_MMIO_DEVICES   \
> @@ -86,6 +88,39 @@ static void xen_create_virtio_mmio_devices(XenArmState 
> *xam)
>      }
>  }
>  
> +static void xen_init_ram(MachineState *machine)
> +{
> +    MemoryRegion *sysmem = get_system_memory();
> +    ram_addr_t block_len, ram_size[GUEST_RAM_BANKS];
> +
> +    if (machine->ram_size <= GUEST_RAM0_SIZE) {
> +        ram_size[0] = machine->ram_size;
> +        ram_size[1] = 0;
> +        block_len = GUEST_RAM0_BASE + ram_size[0];
> +    } else {
> +        ram_size[0] = GUEST_RAM0_SIZE;
> +        ram_size[1] = machine->ram_size - GUEST_RAM0_SIZE;
> +        block_len = GUEST_RAM1_BASE + ram_size[1];
> +    }
> +
> +    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len,
> +                           &error_fatal);
> +
> +    memory_region_init_alias(&ram_lo, NULL, "xen.ram.lo", &ram_memory,
> +                             GUEST_RAM0_BASE, ram_size[0]);
> +    memory_region_add_subregion(sysmem, GUEST_RAM0_BASE, &ram_lo);
> +    DPRINTF("Initialized region xen.ram.lo: base 0x%llx size 0x%lx\n",
> +            GUEST_RAM0_BASE, ram_size[0]);
> +
> +    if (ram_size[1] > 0) {
> +        memory_region_init_alias(&ram_hi, NULL, "xen.ram.hi", &ram_memory,
> +                                 GUEST_RAM1_BASE, ram_size[1]);
> +        memory_region_add_subregion(sysmem, GUEST_RAM1_BASE, &ram_hi);
> +        DPRINTF("Initialized region xen.ram.hi: base 0x%llx size 0x%lx\n",
> +                GUEST_RAM1_BASE, ram_size[1]);
> +    }
> +}
> +
>  void arch_handle_ioreq(XenIOState *state, ioreq_t *req)
>  {
>      hw_error("Invalid ioreq type 0x%x\n", req->type);
> @@ -135,6 +170,14 @@ static void xen_arm_init(MachineState *machine)
>  
>      xam->state =  g_new0(XenIOState, 1);
>  
> +    if (machine->ram_size == 0) {
> +        DPRINTF("ram_size not specified. QEMU machine will be started 
> without"
> +                " TPM, IOREQ and Virtio-MMIO backends\n");
> +        return;
> +    }

I would say "ram_size not specified. QEMU machine started without IOREQ
(no emulated devices including Virtio)."

We might add more devices in the future beyond Virtio and TPM. I don't
think we want to call out the whole list here.



> +    xen_init_ram(machine);
> +
>      xen_register_ioreq(xam->state, machine->smp.cpus, xen_memory_listener);
>  
>      xen_create_virtio_mmio_devices(xam);
> @@ -182,6 +225,8 @@ static void xen_arm_machine_class_init(ObjectClass *oc, 
> void *data)
>      mc->init = xen_arm_init;
>      mc->max_cpus = 1;
>      mc->default_machine_opts = "accel=xen";
> +    /* Set explicitly here to make sure that real ram_size is passed */
> +    mc->default_ram_size = 0;
>  
>      printf("CHECK for NEW BUILD\n");
>  #ifdef CONFIG_TPM
> -- 
> 2.25.1
>