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Re: [PATCH v3 3/3] arm/efi: load dom0 modules from DT using UEFI



On Tue, 28 Sep 2021, Luca Fancellu wrote:
> Add support to load Dom0 boot modules from
> the device tree using the uefi,binary property.
> 
> Update documentation about that.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>

It is great how simple this patch is!

The patch looks all correct. Only one question: do we need a check to
make sure the dom0 ramdisk is not loaded twice? Once via uefi,binary and
another time via the config file? In other words...

> ---
> Changes in v3:
> - new patch
> ---
>  docs/misc/arm/device-tree/booting.txt |  8 ++++
>  docs/misc/efi.pandoc                  | 64 +++++++++++++++++++++++++--
>  xen/arch/arm/efi/efi-boot.h           | 36 +++++++++++++--
>  xen/common/efi/boot.c                 | 12 ++---
>  4 files changed, 108 insertions(+), 12 deletions(-)
> 
> diff --git a/docs/misc/arm/device-tree/booting.txt 
> b/docs/misc/arm/device-tree/booting.txt
> index 354bb43fe1..e73f6476d4 100644
> --- a/docs/misc/arm/device-tree/booting.txt
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -70,6 +70,14 @@ Each node contains the following properties:
>       priority of this field vs. other mechanisms of specifying the
>       bootargs for the kernel.
>  
> +- uefi,binary (UEFI boot only)
> +
> +     String property that specifies the file name to be loaded by the UEFI
> +     boot for this module. If this is specified, there is no need to specify
> +     the reg property because it will be created by the UEFI stub on boot.
> +     This option is needed only when UEFI boot is used, the node needs to be
> +     compatible with multiboot,kernel or multiboot,ramdisk.
> +
>  Examples
>  ========
>  
> diff --git a/docs/misc/efi.pandoc b/docs/misc/efi.pandoc
> index 800e67a233..4cebc47a18 100644
> --- a/docs/misc/efi.pandoc
> +++ b/docs/misc/efi.pandoc
> @@ -167,6 +167,28 @@ sbsign \
>       --output xen.signed.efi \
>       xen.unified.efi
>  ```
> +## UEFI boot and Dom0 modules on ARM
> +
> +When booting using UEFI on ARM, it is possible to specify the Dom0 modules
> +directly from the device tree without using the Xen configuration file, here 
> an
> +example:
> +
> +chosen {
> +     #size-cells = <0x1>;
> +     #address-cells = <0x1>;
> +     xen,xen-bootargs = "[Xen boot arguments]"
> +
> +     module@1 {
> +             compatible = "multiboot,kernel", "multiboot,module";
> +             uefi,binary = "vmlinuz-3.0.31-0.4-xen";
> +             bootargs = "[domain 0 command line options]";
> +     };
> +
> +     module@2 {
> +             compatible = "multiboot,ramdisk", "multiboot,module";
> +             uefi,binary = "initrd-3.0.31-0.4-xen";
> +     };
> +}
>  
>  ## UEFI boot and dom0less on ARM
>  
> @@ -326,10 +348,10 @@ chosen {
>  ### Boot Xen, Dom0 and DomU(s)
>  
>  This configuration is a mix of the two configuration above, to boot this one
> -the configuration file must be processed so the /chosen node must have the
> -"uefi,cfg-load" property.
> +the configuration file can be processed or the Dom0 modules can be read from
> +the device tree.
>  
> -Here an example:
> +Here the first example:
>  
>  Xen configuration file:
>  
> @@ -369,4 +391,40 @@ chosen {
>  };
>  ```
>  
> +Here the second example:
> +
> +Device tree:
> +
> +```
> +chosen {
> +     #size-cells = <0x1>;
> +     #address-cells = <0x1>;
> +     xen,xen-bootargs = "[Xen boot arguments]"
> +
> +     module@1 {
> +             compatible = "multiboot,kernel", "multiboot,module";
> +             uefi,binary = "vmlinuz-3.0.31-0.4-xen";
> +             bootargs = "[domain 0 command line options]";
> +     };
> +
> +     module@2 {
> +             compatible = "multiboot,ramdisk", "multiboot,module";
> +             uefi,binary = "initrd-3.0.31-0.4-xen";
> +     };
> +
> +     domU1 {
> +             #size-cells = <0x1>;
> +             #address-cells = <0x1>;
> +             compatible = "xen,domain";
> +             cpus = <0x1>;
> +             memory = <0x0 0xc0000>;
> +             vpl011;
>  
> +             module@1 {
> +                     compatible = "multiboot,kernel", "multiboot,module";
> +                     uefi,binary = "Image-domu1.bin";
> +                     bootargs = "console=ttyAMA0 root=/dev/ram0 rw";
> +             };
> +     };
> +};
> +```
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index 4f7c913f86..df63387136 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -31,8 +31,10 @@ static unsigned int __initdata modules_idx;
>  #define ERROR_MISSING_DT_PROPERTY   (-3)
>  #define ERROR_RENAME_MODULE_NAME    (-4)
>  #define ERROR_SET_REG_PROPERTY      (-5)
> +#define ERROR_DOM0_ALREADY_FOUND    (-6)
>  #define ERROR_DT_MODULE_DOMU        (-1)
>  #define ERROR_DT_CHOSEN_NODE        (-2)
> +#define ERROR_DT_MODULE_DOM0        (-3)
>  
>  void noreturn efi_xen_start(void *fdt_ptr, uint32_t fdt_size);
>  void __flush_dcache_area(const void *vaddr, unsigned long size);
> @@ -45,7 +47,8 @@ static int allocate_module_file(EFI_FILE_HANDLE dir_handle,
>  static int handle_module_node(EFI_FILE_HANDLE dir_handle,
>                                int module_node_offset,
>                                int reg_addr_cells,
> -                              int reg_size_cells);
> +                              int reg_size_cells,
> +                              bool is_domu_module);
>  static bool is_boot_module(int dt_module_offset);
>  static int handle_dom0less_domain_node(EFI_FILE_HANDLE dir_handle,
>                                         int domain_node);
> @@ -701,7 +704,8 @@ static int __init allocate_module_file(EFI_FILE_HANDLE 
> dir_handle,
>  static int __init handle_module_node(EFI_FILE_HANDLE dir_handle,
>                                       int module_node_offset,
>                                       int reg_addr_cells,
> -                                     int reg_size_cells)
> +                                     int reg_size_cells,
> +                                     bool is_domu_module)
>  {
>      const void *uefi_name_prop;
>      char mod_string[24]; /* Placeholder for module@ + a 64-bit number + \0 */
> @@ -743,6 +747,24 @@ static int __init handle_module_node(EFI_FILE_HANDLE 
> dir_handle,
>          return ERROR_SET_REG_PROPERTY;
>      }
>  
> +    if ( !is_domu_module &&
> +         (fdt_node_check_compatible(fdt, module_node_offset,
> +                                    "multiboot,kernel") == 0) )
> +    {
> +        /*
> +         * This is the Dom0 kernel, wire it to the kernel variable because it
> +         * will be verified by the shim lock protocol later in the common 
> code.
> +         */
> +        if ( kernel.addr )
> +        {
> +            PrintMessage(L"Dom0 kernel already found in cfg file.");
> +            return ERROR_DOM0_ALREADY_FOUND;
> +        }
> +        kernel.need_to_free = false; /* Freed using the module array */
> +        kernel.addr = file->addr;
> +        kernel.size = file->size;
> +    }

... is it necessary to update ramdisk as well or check if it is already
set? As far as I can tell it is the only other potential conflict that
we could have.


>      return 0;
>  }
>  
> @@ -799,7 +821,7 @@ static int __init 
> handle_dom0less_domain_node(EFI_FILE_HANDLE dir_handle,
>          if ( is_boot_module(module_node) )
>          {
>              int ret = handle_module_node(dir_handle, module_node, addr_cells,
> -                                         size_cells);
> +                                         size_cells, true);
>              if ( ret < 0 )
>                  return ret;
>          }
> @@ -809,7 +831,7 @@ static int __init 
> handle_dom0less_domain_node(EFI_FILE_HANDLE dir_handle,
>  
>  /*
>   * This function checks for xen domain nodes under the /chosen node for 
> possible
> - * domU guests to be loaded.
> + * dom0 and domU guests to be loaded.
>   * Returns the number of modules loaded or a negative number for error.
>   */
>  static int __init efi_arch_check_dt_boot(EFI_FILE_HANDLE dir_handle)
> @@ -836,6 +858,12 @@ static int __init efi_arch_check_dt_boot(EFI_FILE_HANDLE 
> dir_handle)
>              if ( handle_dom0less_domain_node(dir_handle, node) < 0 )
>                  return ERROR_DT_MODULE_DOMU;
>          }
> +        else if ( is_boot_module(node) )
> +        {
> +            if ( handle_module_node(dir_handle, node, addr_len, size_len,
> +                                    false) < 0 )
> +                return ERROR_DT_MODULE_DOM0;
> +        }
>      }
>  
>      /* Free dom0less file names if any */
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index c8c57fbb54..b221494a06 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -1296,11 +1296,6 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
> *SystemTable)
>          {
>              read_file(dir_handle, s2w(&name), &kernel, option_str);
>              efi_bs->FreePool(name.w);
> -
> -            if ( !EFI_ERROR(efi_bs->LocateProtocol(&shim_lock_guid, NULL,
> -                            (void **)&shim_lock)) &&
> -                 (status = shim_lock->Verify(kernel.ptr, kernel.size)) != 
> EFI_SUCCESS )
> -                PrintErrMesg(L"Dom0 kernel image could not be verified", 
> status);
>          }
>  
>          if ( !read_section(loaded_image, L"ramdisk", &ramdisk, NULL) )
> @@ -1372,6 +1367,13 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
> *SystemTable)
>      if (dt_module_found < 0)
>          /* efi_arch_check_dt_boot throws some error */
>          blexit(L"Error processing boot modules on DT.");
> +
> +    /* If Dom0 is specified, verify it */
> +    if ( kernel.ptr &&
> +         !EFI_ERROR(efi_bs->LocateProtocol(&shim_lock_guid, NULL,
> +                                           (void **)&shim_lock)) &&
> +        (status = shim_lock->Verify(kernel.ptr, kernel.size)) != EFI_SUCCESS 
> )
> +        PrintErrMesg(L"Dom0 kernel image could not be verified", status);
>      /*
>       * Check if a proper configuration is provided to start Xen:
>       *  - Dom0 specified (minimum required)
> -- 
> 2.17.1
> 



 


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