Re: [Xen-devel] [PATCH RFC 3/4] hvmloader/ovmf: setup ovmf_info

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2013-11-15 at 15:59 +0000, Wei Liu wrote:
> OVMF info contains E820 map allocated by hvmloader. This info is passed
> to OVMF to help it do proper initialization.
> 
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  tools/firmware/hvmloader/ovmf.c |   39 
> +++++++++++++++++++++++++++++++++++++--
>  1 file changed, 37 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/firmware/hvmloader/ovmf.c b/tools/firmware/hvmloader/ovmf.c
> index 7826095..c253083 100644
> --- a/tools/firmware/hvmloader/ovmf.c
> +++ b/tools/firmware/hvmloader/ovmf.c
> @@ -46,10 +46,45 @@
>  #define LOWCHUNK_SIZE           0x00010000
>  #define LOWCHUNK_MAXOFFSET      0x0000FFFF
>  #define LOWCHUNK_END            (OVMF_BEGIN + OVMF_SIZE)
> +#define OVMF_INFO_PHYSICAL_ADDRESS 0X00001000
>  
>  extern unsigned char dsdt_anycpu[];
>  extern int dsdt_anycpu_len;
>  
> +struct ovmf_info {
> +    char signature[11]; /* XenHVMOVMF\0 */
> +    uint8_t length;     /* Length of this struct */
> +    uint8_t checksum;   /* Set such that the sum over bytes 0..length == 0 */

You will need some explicit zero padding (to make the above add up to 16
bytes), otherwise there will be a hole in the struct which might cause
confusion when checksumming (i..e forgetting to sum the hole...)

Or you could add some nulls to the signature.

I wonder if we could share some/all of this with the Seabios code, just
with a different signature and potentially the info address?

> +    /*
> +     * Physical address of the e820 table, contains e820_nr entries.
> +     */
> +    uint32_t e820;
> +    uint32_t e820_nr;
> +} __attribute__ ((packed));
> +
> +static void ovmf_setup_bios_info(void)
> +{
> +    struct ovmf_info *info = (void *)OVMF_INFO_PHYSICAL_ADDRESS;
> +
> +    memset(info, 0, sizeof(*info));
> +
> +    memcpy(info->signature, "XenHVMOVMF", sizeof(info->signature));
> +    info->length = sizeof(*info);
> +}
> +
> +static void ovmf_finish_bios_info(void)
> +{
> +    struct ovmf_info *info = (void *)OVMF_INFO_PHYSICAL_ADDRESS;
> +    uint32_t i;
> +    uint8_t checksum;
> +
> +    checksum = 0;
> +    for ( i = 0; i < info->length; i++ )
> +        checksum += ((uint8_t *)(info))[i];
> +
> +    info->checksum = -checksum;
> +}
> +
>  static void ovmf_load(const struct bios_config *config)
>  {
>      xen_pfn_t mfn;
> @@ -104,8 +139,8 @@ struct bios_config ovmf_config =  {
>  
>      .load_roms = 0,
>  
> -    .bios_info_setup = NULL,
> -    .bios_info_finish = NULL,
> +    .bios_info_setup = ovmf_setup_bios_info,
> +    .bios_info_finish = ovmf_finish_bios_info,
>  
>      .e820_setup = NULL,
>  



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