From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com>
Subject: Re: HVMlite ABI specification DRAFT A
Date: Thu, 4 Feb 2016 20:21:24 +0100
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To: Samuel Thibault <samuel.thibault@ens-lyon.org>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, xen-devel <xen-devel@lists.xenproject.org>, Wei Liu <wei.liu2@citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Tim Deegan <tim@xen.org>, Paul Durrant <paul.durrant@citrix.com>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <JBeulich@suse.com>
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El 4/2/16 a les 19:51, Samuel Thibault ha escrit:
> Boris Ostrovsky, on Thu 04 Feb 2016 13:38:02 -0500, wrote:
>> On 02/04/2016 12:48 PM, Roger Pau Monn=E9 wrote:
>>> The format of the boot start info structure is the following (pointed to
>>> be %ebx):
>>>
>>>     struct hvm_start_info {
>>>     #define HVM_START_MAGIC_VALUE 0x336ec578
>>>         uint32_t magic;             /* Contains the magic value 0x336ec=
578       */
>>>                                     /* ("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.    =
          */
>>>     };
>>
>> If there is more than one module, how is the guest expected to sort out
>> which module is what?

In general I was expecting this would be done by position, or if that's
not enough an additional module (at either position 0 or n) should be
passed to contain that information.

> +1
> We need that to pass parameters to gnumach modules.

Hm, parameters as in a string that's paired with a module, or something
more complex like a metadata block?

I see that multiboot provides a string associated with each module, we
could do the same IMHO. I'm fine with adding it to the boot ABI, but I
would prefer if someone with access to such an OS does the actual
implementation of this feature.

Just to be clear that we are on the same page, then the _entry struct
becomes:

struct hvm_modlist_entry {
	uint32_t paddr;
	uint32_t size;
	uint32_t cmdline_paddr;
};

cmdline_paddr would work the same way as it does in the hvm_start_info
struct (ie: physical address of a zero-terminated ASCII string).

I think I'm going to re-write this in binary form (getting rid of the
structs), or else people are going to get the implementation wrong due
to paddings.

Roger.