Re: [RFC PATCH 4/9] hvm: Introduce "fixed memory layout" feature

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Le 01/09/2025 à 17:50, Jan Beulich a écrit :
> On 29.08.2025 15:32, Teddy Astie wrote:
>> Le 28/08/2025 à 14:30, Jan Beulich a écrit :
>>> On 21.08.2025 17:25, Teddy Astie wrote:
>>>> --- a/xen/include/public/arch-x86/hvm/start_info.h
>>>> +++ b/xen/include/public/arch-x86/hvm/start_info.h
>>>> @@ -99,6 +99,13 @@
>>>>    #define XEN_HVM_MEMMAP_TYPE_DISABLED  6
>>>>    #define XEN_HVM_MEMMAP_TYPE_PMEM      7
>>>>
>>>> +/* Xen-specific types (OEM-specific range of the ACPI spec) */
>>>> +#define XEN_HVM_MEMMAP_TYPE_SHARED_INFO   0xF0000001 /* Shared info page 
>>>> */
>>>> +#define XEN_HVM_MEMMAP_TYPE_GRANT_TABLE   0xF0000002 /* Grant table pages 
>>>> */
>>>> +#define XEN_HVM_MEMMAP_TYPE_GNTTAB_STATUS 0xF0000003 /* Grant table 
>>>> status page (v2) */
>>>> +#define XEN_HVM_MEMMAP_TYPE_FOREIGN_REG   0xF0000004 /* Suitable region 
>>>> for grant mappings */
>>>> +                                                     /* and foreign 
>>>> mappings */
>>>
>>> I question it being legitimate for us to introduce new E820 types.
>>
>> These E820 types are (at least in ACPI specification) in the OEM-defined
>> range which seems appropriate for me to use for Xen-specific mappings.
>
> Just that we're not an OEM.

How should such information be provided alternatively ?

Currently, premapped pages (xenstore, PV console, ...) locations are
provided through hvm parameters, but I don't think introducing new hvm
parameters is very wise.

One way of another, we would need to provide to the guest a xen-specific
memory map for implementing this.

>
> Jan
>



--
Teddy Astie | Vates XCP-ng Developer

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