Re: [PATCH v4 3/3] arm/efi: load dom0 modules from DT using UEFI

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Luca,

> On 30 Sep 2021, at 15:28, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> 
> Add support to load Dom0 boot modules from
> the device tree using the xen,uefi-binary property.
> 
> Update documentation about that.
> 
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Changes in v4:
> - Add check to avoid double definition of Dom0 ramdisk
> from cfg file and DT
> - Fix if conditions indentation in boot.c
> - Moved Dom0 kernel verification code after check for
> presence for Dom0 or DomU(s)
> - Changed uefi,binary property to xen,uefi-binary
> 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           | 47 ++++++++++++++++++--
> xen/common/efi/boot.c                 | 16 ++++---
> 4 files changed, 123 insertions(+), 12 deletions(-)
> 
> diff --git a/docs/misc/arm/device-tree/booting.txt 
> b/docs/misc/arm/device-tree/booting.txt
> index 7258e7e1ec..8e0c327ba4 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 876cd55005..4abbb5bb82 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";
> +             xen,uefi-binary = "vmlinuz-3.0.31-0.4-xen";
> +             bootargs = "[domain 0 command line options]";
> +     };
> +
> +     module@2 {
> +             compatible = "multiboot,ramdisk", "multiboot,module";
> +             xen,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
> -"xen,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";
> +             xen,uefi-binary = "vmlinuz-3.0.31-0.4-xen";
> +             bootargs = "[domain 0 command line options]";
> +     };
> +
> +     module@2 {
> +             compatible = "multiboot,ramdisk", "multiboot,module";
> +             xen,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";
> +                     xen,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 50b3829ae0..b122e2846a 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -31,8 +31,11 @@ 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_DOM0_RAMDISK_FOUND    (-7)
> #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 +48,8 @@ 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 +705,8 @@ 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 +748,34 @@ static int __init handle_module_node(EFI_FILE_HANDLE 
> dir_handle,
>         return ERROR_SET_REG_PROPERTY;
>     }
> 
> +    if ( !is_domu_module )
> +    {
> +        if ( (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;
> +        }
> +        else if ( ramdisk.addr &&
> +                  (fdt_node_check_compatible(fdt, module_node_offset,
> +                                             "multiboot,ramdisk") == 0) )
> +        {
> +            PrintMessage(L"Dom0 ramdisk already found in cfg file.");
> +            return ERROR_DOM0_RAMDISK_FOUND;
> +        }
> +    }
> +
>     return 0;
> }
> 
> @@ -799,7 +832,7 @@ 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 +842,7 @@ 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 +869,12 @@ 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 boot modules file names if any */
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index daf7c26099..e4295dbe34 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) )
> @@ -1385,6 +1380,17 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
> *SystemTable)
>     if ( !dt_modules_found && !kernel.addr )
>         blexit(L"No Dom0 kernel image specified.");
> 
> +    /*
> +     * The Dom0 kernel can be loaded from the configuration file or by the
> +     * device tree through the efi_arch_check_dt_boot function, in this stage
> +     * verify it.
> +     */
> +    if ( kernel.addr &&
> +         !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);
> +
>     efi_arch_edd();
> 
>     /* XXX Collect EDID info. */
> -- 
> 2.17.1
>