Re: [QEMU][PATCH v4 2/2] xen_arm: Initialize RAM and add hi/low memory regions

[Stefano Stabellini]

On Tue, 29 Aug 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 and other
> emulated devices like TPM and VIRTIO. This is done to keep this QEMU machine
> usable for /etc/init.d/xencommons.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  hw/arm/xen_arm.c            | 45 +++++++++++++++++++++++++++++++++++++
>  include/hw/xen/xen_native.h |  8 +++++++
>  2 files changed, 53 insertions(+)
> 
> diff --git a/hw/arm/xen_arm.c b/hw/arm/xen_arm.c
> index 7393b37355..f83b983ec5 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;
> +
>  /*
>   * VIRTIO_MMIO_DEV_SIZE is imported from tools/libs/light/libxl_arm.c under 
> Xen
>   * repository.
> @@ -92,6 +94,39 @@ 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);
> @@ -141,6 +176,14 @@ 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 started without IOREQ"
> +                "(no emulated devices including Virtio)\n");
> +        return;
> +    }
> +
> +    xen_init_ram(machine);
> +
>      xen_register_ioreq(xam->state, machine->smp.cpus, &xen_memory_listener);
>  
>      xen_create_virtio_mmio_devices(xam);
> @@ -188,6 +231,8 @@ 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;
>  
>  #ifdef CONFIG_TPM
>      object_class_property_add(oc, "tpm-base-addr", "uint64_t",
> diff --git a/include/hw/xen/xen_native.h b/include/hw/xen/xen_native.h
> index a4b1aa9e5d..5d2718261f 100644
> --- a/include/hw/xen/xen_native.h
> +++ b/include/hw/xen/xen_native.h
> @@ -539,4 +539,12 @@ static inline int 
> xendevicemodel_set_irq_level(xendevicemodel_handle *dmod,
>  #define GUEST_VIRTIO_MMIO_SPI_LAST    43
>  #endif
>  
> +#if defined(__i386__) || defined(__x86_64__)
> +#define GUEST_RAM_BANKS   2
> +#define GUEST_RAM0_BASE   0x40000000ULL /* 3GB of low RAM @ 1GB */
> +#define GUEST_RAM0_SIZE   0xc0000000ULL
> +#define GUEST_RAM1_BASE   0x0200000000ULL /* 1016GB of RAM @ 8GB */
> +#define GUEST_RAM1_SIZE   0xfe00000000ULL
> +#endif
> +
>  #endif /* QEMU_HW_XEN_NATIVE_H */
> -- 
> 2.17.1
>