Re: [PATCH 1/1] x86/PVHv2: Add memory map pointer to hvm_start_info struct

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Mar 02, 2018 at 12:54:29PM -0800, Maran Wilson wrote:
> The start info structure that is defined as part of the x86/HVM direct boot
> ABI and used for starting Xen PVH guests would be more versatile if it also
> included a way to pass information about the memory map to the guest. This
> would allow KVM guests to share the same entry point.

Would it be better if there was an tag/length as well? And maybe more dynamic
so that if you want to add more structures you can identify them tags?
Like what Multiboot2 has?

> 
> Signed-off-by: Maran Wilson <maran.wilson@oracle.com>
> ---
>  xen/include/public/arch-x86/hvm/start_info.h | 51 +++++++++++++++++++++++++++-
>  1 file changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/include/public/arch-x86/hvm/start_info.h b/xen/include/public/arch-x86/hvm/start_info.h
> index 6484159..ae8dac8 100644
> --- a/xen/include/public/arch-x86/hvm/start_info.h
> +++ b/xen/include/public/arch-x86/hvm/start_info.h
> @@ -33,8 +33,9 @@
>   *    | magic          | Contains the magic value XEN_HVM_START_MAGIC_VALUE
>   *    |                | ("xEn3" with the 0x80 bit of the "E" set).
>   *  4 +----------------+
> - *    | version        | Version of this structure. Current version is 0. New
> + *    | version        | Version of this structure. Current version is 1. New
>   *    |                | versions are guaranteed to be backwards-compatible.
> + *    |                | For PV guests only 0 allowed, for PVH 0 or 1 allowed.
>   *  8 +----------------+
>   *    | flags          | SIF_xxx flags.
>   * 12 +----------------+
> @@ -48,6 +49,15 @@
>   * 32 +----------------+
>   *    | rsdp_paddr     | Physical address of the RSDP ACPI data structure.
>   * 40 +----------------+
> + *    | memmap_paddr   | Physical address of the (optional) memory map. Only
> + *    |                | present in version 1 and newer of the structure.
> + * 48 +----------------+
> + *    | memmap_entries | Number of entries in the memory map table. Only
> + *    |                | present in version 1 and newer of the structure.
> + *    |                | Zero if there is no memory map being provided.
> + * 52 +----------------+
> + *    | reserved       | Version 1 and newer only.
> + * 56 +----------------+
>   *
>   * The layout of each entry in the module structure is the following:
>   *
> @@ -62,10 +72,34 @@
>   *    | reserved       |
>   * 32 +----------------+
>   *
> + * The layout of each entry in the memory map table is as follows:
> + *
> + *  0 +----------------+
> + *    | addr           | Base address
> + *  8 +----------------+
> + *    | size           | Size of mapping in bytes
> + * 16 +----------------+
> + *    | type           | Type of mapping as defined between the hypervisor
> + *    |                | and guest it's starting. E820_TYPE_xxx, for example.
> + * 20 +----------------|
> + *    | reserved       |
> + * 24 +----------------+
> + *
>   * The address and sizes are always a 64bit little endian unsigned integer.
>   *
>   * NB: Xen on x86 will always try to place all the data below the 4GiB
>   * boundary.
> + *
> + * Version numbers of the hvm_start_info structure have evolved like this:
> + *
> + * Version 0:
> + *
> + * Version 1:	Added the memmap_paddr/memmap_entries fields (plus 4 bytes of
> + *		padding) to the end of the hvm_start_info struct. These new
> + *		fields can be used to pass a memory map to the guest. The
> + *		memory map is optional and so guests that understand version 1
> + *		of the structure must check that memmap_entries is non-zero
> + *		before trying to read the memory map.
>   */
>  #define XEN_HVM_START_MAGIC_VALUE 0x336ec578
>  
> @@ -86,6 +120,14 @@ struct hvm_start_info {
>      uint64_t cmdline_paddr;     /* Physical address of the command line.     */
>      uint64_t rsdp_paddr;        /* Physical address of the RSDP ACPI data    */
>                                  /* structure.                                */
> +    uint64_t memmap_paddr;	/* Physical address of an array of           */
> +				/* hvm_memmap_table_entry. Only present in   */
> +				/* version 1 and newer of the structure      */
> +    uint32_t memmap_entries;	/* Number of entries in the memmap table.    */
> +				/* Only present in version 1 and newer of    */
> +				/* the structure. Value will be zero if      */
> +				/* there is no memory map being provided.    */
> +    uint32_t reserved;
>  };
>  
>  struct hvm_modlist_entry {
> @@ -95,4 +137,11 @@ struct hvm_modlist_entry {
>      uint64_t reserved;
>  };
>  
> +struct hvm_memmap_table_entry {
> +    uint64_t addr;		/* Base address of the memory region         */
> +    uint64_t size;		/* Size of the memory region in bytes        */
> +    uint32_t type;		/* Mapping type                              */
> +    uint32_t reserved;
> +};
> +
>  #endif /* __XEN_PUBLIC_ARCH_X86_HVM_START_INFO_H__ */
> -- 
> 1.8.3.1
> 
> 
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