Re: [PATCH v4 1/4] x86/HVM: update the start info structure layout

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Roger Pau Monne, on Tue 16 Feb 2016 18:37:46 +0100, wrote:
> After some discussion around the new boot ABI consensus has been reached
> about the layout and contents of the start info. The following patch updates
> the layout to what has been agreed.
> 
> Also, the new layout is described in binary terms in order to avoid issues
> with alignments when using C structs.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
> Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Ian Campbell <ian.campbell@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
>  tools/libxc/include/xc_dom.h | 31 +++++++++++++++++++++++++
>  xen/include/public/xen.h     | 55 ++++++++++++++++++++++++++++++--------------
>  2 files changed, 69 insertions(+), 17 deletions(-)
> 
> diff --git a/tools/libxc/include/xc_dom.h b/tools/libxc/include/xc_dom.h
> index cac4698..6ebe946 100644
> --- a/tools/libxc/include/xc_dom.h
> +++ b/tools/libxc/include/xc_dom.h
> @@ -216,6 +216,37 @@ struct xc_dom_image {
>      struct xc_hvm_firmware_module smbios_module;
>  };
>  
> +#if defined(__i386__) || defined(__x86_64__)
> +/* C representation of the x86/HVM start info layout.
> + *
> + * The canonical definition of this layout resides in public/xen.h, this
> + * is just a way to represent the layout described there using C types.
> + *
> + * NB: the packed attribute is not really needed, but it helps us enforce
> + * the fact this this is just a representation, and it might indeed
> + * be required in the future if there are alignment changes.
> + */
> +struct hvm_start_info {
> +    uint32_t magic;             /* Contains the magic value 0x336ec578       */
> +                                /* ("xEn3" with the 0x80 bit of the "E" set).*/
> +    uint32_t version;           /* Version of this structure.                */
> +    uint32_t flags;             /* SIF_xxx flags.                            */
> +    uint32_t cmdline_paddr;     /* Physical address of the command line.     */
> +    uint32_t nr_modules;        /* Number of modules passed to the kernel.   */
> +    uint32_t modlist_paddr;     /* Physical address of an array of           */
> +                                /* hvm_modlist_entry.                        */
> +    uint32_t rsdp_paddr;        /* Physical address of the RSDP ACPI data    */
> +                                /* structure.                                */
> +} __attribute__((packed));
> +
> +struct hvm_modlist_entry {
> +    uint64_t paddr;             /* Physical address of the module.           */
> +    uint64_t size;              /* Size of the module in bytes.              */
> +    uint64_t cmdline_paddr;     /* Physical address of the command line.     */
> +    uint64_t reserved;
> +} __attribute__((packed));
> +#endif /* x86 */
> +
>  /* --- pluggable kernel loader ------------------------------------- */
>  
>  struct xc_dom_loader {
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index 7b629b1..6ba060f 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -787,25 +787,46 @@ typedef struct start_info start_info_t;
>  /*
>   * Start of day structure passed to PVH guests in %ebx.
>   *
> - * NOTE: nothing will be loaded at physical address 0, so
> - * a 0 value in any of the address fields should be treated
> - * as not present.
> + * NOTE: nothing will be loaded at physical address 0, so a 0 value in any
> + * of the address fields should be treated as not present.
> + *
> + *  0 +----------------+
> + *    | magic          | Contains the magic value HVM_START_MAGIC_VALUE
> + *    |                | ("xEn3" with the 0x80 bit of the "E" set).
> + *  4 +----------------+
> + *    | version        | Version of this structure. Current version is 0. New
> + *    |                | versions are guaranteed to be backwards-compatible.
> + *  8 +----------------+
> + *    | flags          | SIF_xxx flags.
> + * 12 +----------------+
> + *    | cmdline_paddr  | Physical address of the command line,
> + *    |                | a zero-terminated ASCII string.
> + * 16 +----------------+
> + *    | nr_modules     | Number of modules passed to the kernel.
> + * 20 +----------------+
> + *    | modlist_paddr  | Physical address of an array of modules
> + *    |                | (layout of the structure below).
> + * 24 +----------------+
> + *    | rsdp_paddr     | Physical address of the RSDP ACPI data structure.
> + * 28 +----------------+
> + *
> + * The layout of each entry in the module structure is the following:
> + *
> + *  0 +----------------+
> + *    | paddr          | Physical address of the module.
> + *  8 +----------------+
> + *    | size           | Size of the module in bytes.
> + * 16 +----------------+
> + *    | cmdline_paddr  | Physical address of the command line,
> + *    |                | a zero-terminated ASCII string.
> + * 24 +----------------+
> + *    | reserved       |
> + * 32 +----------------+
> + *
> + * The address and size of the modules is a 64bit unsigned integer. However
> + * Xen will always try to place all modules below the 4GiB boundary.
>   */
> -struct hvm_start_info {
>  #define HVM_START_MAGIC_VALUE 0x336ec578
> -    uint32_t magic;             /* Contains the magic value 0x336ec578       */
> -                                /* ("xEn3" with the 0x80 bit of the "E" set).*/
> -    uint32_t flags;             /* SIF_xxx flags.                            */
> -    uint32_t cmdline_paddr;     /* Physical address of the command line.     */
> -    uint32_t nr_modules;        /* Number of modules passed to the kernel.   */
> -    uint32_t modlist_paddr;     /* Physical address of an array of           */
> -                                /* hvm_modlist_entry.                        */
> -};
> -
> -struct hvm_modlist_entry {
> -    uint32_t paddr;             /* Physical address of the module.           */
> -    uint32_t size;              /* Size of the module in bytes.              */
> -};
>  
>  /* New console union for dom0 introduced in 0x00030203. */
>  #if __XEN_INTERFACE_VERSION__ < 0x00030203
> -- 
> 2.5.4 (Apple Git-61)
> 

-- 
Samuel
<N> un driver qui fait quoi, alors ?
<y> ben pour les bips
<s> pour passer les oops en morse
 -+- #ens-mim - vive les rapports de bug -+-