Re: [Xen-devel] [PATCH v4 06/14] xen: Move the hvm_start_info C representation from libxc to public/xen.h

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.03.16 at 18:55, <anthony.perard@xxxxxxxxxx> wrote:
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -841,6 +841,37 @@ typedef struct start_info start_info_t;
>   */
>  #define XEN_HVM_START_MAGIC_VALUE 0x336ec578
>  
> +#if defined(__i386__) || defined(__x86_64__)
> +/* C representation of the x86/HVM start info layout.
> + *
> + * The canonical definition of this layout is abrove, 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 */

This needs extra care: Either the packed attributes need to be
dropped (Roger - why did they get put there in the first place?),
or their use needs to be shielded from compilers not understanding
them.

Jan


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