Re: [PATCH] smbios: entry-point-type option

[Laszlo Ersek]

On 12/09/20 19:16, Eduardo Habkost wrote:
> On Wed, Dec 09, 2020 at 09:42:25AM +0000, Daniel P. Berrangé wrote:
>> On Tue, Dec 08, 2020 at 04:20:23PM -0500, Eduardo Habkost wrote:
>>> Add command-line option that lets the SMBIOS entry point type to
>>> be configured.
>>>
>>> SMBIOS 3.0 support is necessary to allow us to support more
>>> than 720 VCPUs in x86_64, due to SMBIOS 2.1 table size limits.
>>>
>>> Note that it's still up to firmware to decide whether to generate
>>> SMBIOS 2.1 and/or 3.0 entry points for the guest, using the
>>> information contained in etc/smbios/smbios-anchor.  OVMF, for
>>> example, is able to generate both entry points, depending on the
>>> value of PcdSmbiosEntryPointProvideMethod.
>>>
>>> The SMBIOS 3.0 entry point won't be enabled by default because it
>>> is not supported yet by Seabios.  This may be changed once
>>> Seabios starts supporting SMBIOS 3.0 entry points.
>>>
>>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>>> ---
>>> Laszlo, Philippe: do you know how exactly the value of
>>> PcdSmbiosEntryPointProvideMethod is chosen when running OVMF?
>>
>> Laszlo proides alot of detail in my original proposal for
>> selecting SMBIOS entry point here:
>>
>> https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg03347.html
> 
> Thanks!
> 
>>
> [...]
>>> diff --git a/qemu-options.hx b/qemu-options.hx
>>> index 104632ea34..d2a973f8a7 100644
>>> --- a/qemu-options.hx
>>> +++ b/qemu-options.hx
>>> @@ -2294,7 +2294,9 @@ DEF("smbios", HAS_ARG, QEMU_OPTION_smbios,
>>>      "                specify SMBIOS type 11 fields\n"
>>>      "-smbios 
>>> type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str]\n"
>>>      "               [,asset=str][,part=str][,speed=%d]\n"
>>> -    "                specify SMBIOS type 17 fields\n",
>>> +    "                specify SMBIOS type 17 fields\n"
>>> +    "-smbios entry-point-type=2.1|3.0\n"
>>> +    "                specify SMBIOS entry point type\n",
>>
>> My previous patch:
>>
>>   https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg03027.html
>>
>> exposed the entry point version as a property on the PC machine
>> rather than the -smbios arg, principally because it is the machin
>> setup code that currently defines what version is used via the calls
>> to smbios_set_defaults().
>>
>> IIUC from Laszlo's reply,  SMBIOS 2.1 is not valid for AArch64
>> at all - they only support 3.0.  So there's a small benefit from
>> configuring this against the PC machine types, because it prevents
>> ability to select 2.1 for ARM SMBIOS which would be invalid.
> 
> Good point.  It would also make it easier to change the machine
> type default in the future.
> 
> I will submit something based on your patches, instead.
> 

Thank you, Daniel, for finding that write-up; I've got it completely
paged-out by now :) I don't have anything to add here, just confirming
that I've read this thread quickly. Eduardo, if you have questions wrt.
OVMF, please let me know; I'll try to find the time.

Thanks!
Laszlo