Re: [Qemu-devel] [PATCH 1/1] target-i386: prevent users from setting threads>1 for AMD CPUs

[Paolo Bonzini <pbonzini@redhat.com>]

Il 08/10/2014 02:41, Wei Huang ha scritto:
> I am OK with either way. The key question is: should QEMU presents
> CPUIDs strictly as specified by the command line or QEMU can tweak a
> little bit on behalf of end-users? For instance, if end-users say "-smp
> 8,cores=2,threads=2,sockets=2", they meant "two socket, each has two
> 2-hyperthread cores". Current QEMU will convert CPUID as "two socket,
> each has 4 cores". My patch will forbid the tweaking...

Understood---it actually looks like it was intentional:

commit 400281af34e5ee6aa9f5496b53d8f82c6fef9319
Author: Andre Przywara <andre.przywara@amd.com>
Date:   Wed Aug 19 15:42:42 2009 +0200

    set CPUID bits to present cores and threads topology
    
    Controlled by the enhanced -smp option set the CPUID bits to present the
    guest the desired topology. This is vendor specific, but (with the exception
    of the CMP_LEGACY bit) not conflicting, so we set all bits everytime.
    There is no real multithreading support for AMD CPUs, so report cores
    instead.
    
    Signed-off-by: Andre Przywara <andre.przywara@amd.com>
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Paolo