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[Qemu-devel] Re: [PATCH][SEABIOS] Make SMBIOS table pass MS SVVP test

From: Sebastian Herbszt
Subject: [Qemu-devel] Re: [PATCH][SEABIOS] Make SMBIOS table pass MS SVVP test
Date: Thu, 26 Nov 2009 22:38:50 +0100

Gleb Natapov wrote:
On Wed, Nov 25, 2009 at 09:09:19PM +0100, Sebastian Herbszt wrote:
Gleb Natapov wrote:
>On Tue, Nov 24, 2009 at 10:57:02AM -0500, Kevin O'Connor wrote:
>>That said, I think SeaBIOS should autodetect any values where that's
>>feasible.  So, for example, if the cpu identification is available via
>>cpuid, then I think that should be used.  However, for example, if cpu
>>model isn't available anywhere, then I think hardcoding something is
>It is used already where appropriate. To fill processor_id field in type
>4 table. CPU manufacturer is different issue. CPU a guest is running on is
>not manufactured by Intel or AMD, it is emulated by QEMU.

I am still wondering why you're against using the vendor reported by CPUID.
I am still wondering why you want this :) But let me ask you a question:
You are running some program inside QEMU and you encounter a bug. Some
instruction does not update eflags like it should and program fails. Do
you complain to
a) AMD
b) Intel
c) QEMU mailing list.

If your answer is (c), then I don't see how you can propose to put
something else then QEMU in manufacturer field.

Since i know i run the program inside QEMU my answer has to be (c). On the other
hand the competition doesn't put "VMware" there.

The cross vendor host cpu migration doesn't seem to be a sound reason, because
the cpu in the guest is emulated and has no relationship to the host cpu.
If i specify "-cpu phenom", i end up with an AMD cpu. Since noone but AMD
produces this cpu it seems only reasonable to advertise the vendor as AMD.

>>> > >>>>>>>-    p->max_speed = 0; /* unknown */
>>> > >>>>>>>-    p->current_speed = 0; /* unknown */
>>> > >>>>>>>+    p->max_speed = 2000;
>>> > >>>>>>>+    p->current_speed = 2000;
>>SeaBIOS detects the current Mhz - see calibrate_tsc() in src/clock.c.
>How accurate is it? What if I boot 100 guests on 16 cpu host
>simultaneously? Not uncommon scenario. Those field really have no
>meaning in virtualization environment. I'd rather have predictable
>values there from boot to boot. Who know what Windows may use them for.

Speaking of not knowing what an OS or application might do with values in the
SMBIOS table. Doesn't the same argument apply to the cpu vendor?

I am concern with SMBIOS table be different on each boot, not what
information is stored in those fields. CPU manufacturer is free form
string. I have computers that have "Intel" there, others have "Intel(R)
Corporation". As long as it consistent from boot to boot it is OK IMO.

Then i must admit i understood your  "Who know what Windows may use them for"
statement different.

- Sebastian

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