Re: [Xen-devel] HVMlite ABI specification DRAFT B + implementation outline

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.02.16 at 17:32, <roger.pau@xxxxxxxxxx> wrote:
> El 9/2/16 a les 14:41, Jan Beulich ha escrit:
>>>>> On 09.02.16 at 14:00, <roger.pau@xxxxxxxxxx> wrote:
>>> Hm, I guess I'm overlooking something, but I think Xen checks the ACPI
>>> tables, see xen/arch/x86/x86_64/mmconfig-shared.c:400:
>>>
>>>     if (pci_mmcfg_check_hostbridge()) {
>>>         unsigned int i;
>>>
>>>         pci_mmcfg_arch_init();
>>>         for (i = 0; i < pci_mmcfg_config_num; ++i)
>>>             if (pci_mmcfg_arch_enable(i))
>>>                 valid = 0;
>>>     } else {
>>>         acpi_table_parse(ACPI_SIG_MCFG, acpi_parse_mcfg);
>>>         pci_mmcfg_arch_init();
>>>         valid = pci_mmcfg_reject_broken();
>>>     }
>>>
>>> Which AFAICT suggests that Xen is indeed able to parse the 'MCFG' table,
>>> which contains the list of MMCFG regions on the system. Is there any
>>> other ACPI table where this information is reported that I'm missing?
>> 
>> You didn't read my reply carefully enough: I didn't say Xen can't
>> parse these tables. What I said is that Xen isn't by itself in the
>> position to do sanity checks that have proven necessary. Hence ...
> 
> Sorry, Ack, AFAICT FreeBSD is much more naive in this aspect and blindly
> trusts what the ACPI MCFG table contains (or at least it seems to me
> that way).
> 
> I'm not going to argue since you say that this has proven necessary, but
> are this kind of broken systems still around? PVH/HVMlite requires
> recent hardware in order to run, so maybe things have improved since
> this was implemented.

Let me not get started on the quality of memory maps various
vendors' UEFI implementations provide.

Jan


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