Re: [Qemu-devel] [PATCH v2 0/3] target-i386: Don't trigger CPUID warnings by default in KVM mode (in most hosts)

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/11/2015 20:58, Eduardo Habkost wrote:
> The x86 change to make "check" mode be enabled by default made QEMU print
> warnings in the default case if running in an Intel host:
> 
>   $ qemu-system-x86_64 -machine pc,accel=kvm
>   warning: host doesn't support requested feature: CPUID.80000001H:ECX.sse4a [bit 6]
> 
> There's also a warning when about missing the ABM feature if running on a Sandy
> Bridge or older host.
> 
> ABM is not available on Sandy Bridge and older, SSE4a is not available in any
> Intel host. We want to make the default CPU runnable in most hosts, so those
> features won't be enabled by default in KVM mode.
> 
> We should eventually have all features supported by TCG enabled by default in
> TCG mode, but as we don't have a good mechanism today to ensure we have
> different defaults in KVM and TCG mode, disable ABM and SSE4a in the qemu64 CPU
> model entirely.
> 
> Also, as we can't change the guest ABI in pc-*-2.4, disable "check" mode by
> default in pc-*-2.4 and older so we don't print spurious warnings.
> 
> Note that with this change, the qemu64 CPU model still requires a host
> supporting POPCNT (Nehalem or newer, and Opteron_G3 or newer).

Do we want to remove that one as well?

> Eduardo Habkost (3):
>   target-i386: Set "check=off" by default on pc-*-2.4 and older
>   target-i386: Remove SSE4a from qemu64 CPU model
>   target-i386: Remove ABM from qemu64 CPU model
> 
>  include/hw/i386/pc.h | 15 +++++++++++++++
>  target-i386/cpu.c    |  3 +--
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 

In any case,

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo