Re: [PATCH v3] hvmloader: indicate ACPI tables with "ACPI data" type in e820

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.09.2020 12:44, Igor Druzhinin wrote:
> On 08/09/2020 10:15, Jan Beulich wrote:
>> On 08.09.2020 01:42, Igor Druzhinin wrote:
>>> @@ -210,8 +223,8 @@ int build_e820_table(struct e820entry *e820,
>>>      {
>>>          uint32_t igd_opregion_base = igd_opregion_pgbase << PAGE_SHIFT;
>>>  
>>> -        e820[nr].addr = RESERVED_MEMBASE;
>>> -        e820[nr].size = (uint32_t) igd_opregion_base - RESERVED_MEMBASE;
>>> +        e820[nr].addr = acpi_mem_end;
>>> +        e820[nr].size = igd_opregion_base - acpi_mem_end;
>>>          e820[nr].type = E820_RESERVED;
>>>          nr++;
>>>  
>>> @@ -227,7 +240,7 @@ int build_e820_table(struct e820entry *e820,
>>>      }
>>>      else
>>>      {
>>> -        e820[nr].addr = RESERVED_MEMBASE;
>>> +        e820[nr].addr = acpi_mem_end;
>>>          e820[nr].size = (uint32_t)-e820[nr].addr;
>>>          e820[nr].type = E820_RESERVED;
>>>          nr++;
>>
>> In both cases - why not RESERVED_MEMORY_DYNAMIC_START? I.e. why
>> mark reserved space that isn't in use for anything?
> 
> I think it's better to reserve space that a) isn't suppose to be in use for 
> anything - 
> we don't really want some MMIO being accidentally mapped there and confusing 
> whatever in
> our fragile model, b) that wasn't a hole before so it'd be dangerous to make 
> it that
> way here. Overall, I think it's better to keep this space as reserved as 
> possible as
> before.

Hmm, yes, fair point. Could you please briefly comment on this in
the code, perhaps by extending an existing comment by half a
sentence?

Jan