On Tue, Nov 03, 2015 at 06:49:08PM +0100, Paolo Bonzini wrote: > > > On 03/11/2015 18:41, Eduardo Habkost wrote: > > I just got a report from David that the lack of ABM on Sandy Bridge > > hosts will trigger the warning, too. I guess we don't want to require a > > Haswell CPU to run the default CPU model with KVM, so ABM would be > > disabled by default in KVM mode too. > > > > We really should make the defaults different in TCG and KVM mode. The > > question is what to do about the TCG defaults in QEMU 2.5. > > > > I propose we remove ABM and SSE4E from qemu64 in 2.5, > > But if we do that for all machine types we break guest ABI for >=Haswell > on old machine types; if we do that for 2.5 only we get "-cpu check" > warnings on old machine types.
I don't propose we remove it from all machine-types, but just from pc-2.5 and newer. > > This is true even if we implement different defaults for KVM and TCG. > Should we disable "-cpu check" for old machine types (or do we already > do that)? That would suck, but it would let us drop ABM and SSE4A from > the 2.4 machine type without much hassle. You mean dropping from the 2.5 machine-type, right? > > > and implement a > > proper mechanism to have different KVM and TCG defaults after 2.5. We > > never pretended that qemu64 had all TCG-supported features enabled > > anyway: the last time the feature set of qemu64 was changed was in 2009 > > (when we added ABM). > > That's true. So, trying to summarize what I would like to do: * Remove ABM and SEE4A from qemu64 in pc-2.5 * Keep ABM and SSE4A in qemu64 in pc-2.4 and older * Disable "check" by default in pc-2.4 and older, to avoid spurious warnings -- Eduardo
