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On versioned CPU models, aliases, and machine types
From: |
Kashyap Chamarthy |
Subject: |
On versioned CPU models, aliases, and machine types |
Date: |
Fri, 15 Oct 2021 12:52:50 +0200 |
Hi
With the versioned CPU models, I see that the plain, non-versioned named
model now says: "alias configured by machine type". For example:
$> qemu-system-x86_64 -cpu help | grep Broadwell
x86 Broadwell (alias configured by machine type)
x86 Broadwell-IBRS (alias of Broadwell-v3)
x86 Broadwell-noTSX (alias of Broadwell-v2)
x86 Broadwell-noTSX-IBRS (alias of Broadwell-v4)
x86 Broadwell-v1 Intel Core Processor (Broadwell)
x86 Broadwell-v2 Intel Core Processor (Broadwell, no TSX)
x86 Broadwell-v3 Intel Core Processor (Broadwell, IBRS)
x86 Broadwell-v4 Intel Core Processor (Broadwell, no TSX, IBRS)
Now, any QEMU binary (qemu-system-x86-6.0.0-1 in my case) supports a ton
of versioned machine types. So when the plain "Broadwell" model says
"alias configured by machine type", I have two questions:
(1) Is there a way to figure out _which_ exact versioned CPU model will
plain "Broadwell" alias to in the above case?
My guess: Assuming I'm using the plain 'q35' machine type (which
aliases to the latest versioned machine type), "Broadwell" will
alias to "Broadwell-v4".
(2) Also, it sounds like depending on the versioned machine type I
configure, the CPU model alias of plain "Broadwell" might change --
is this correct?
(Ideally, I'd like to document an example of each of the above in the
in-tree doc, cpu-models-x86.rst.inc. It's not really obvious.)
--
/kashyap
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