Re: Windows 10 won't run on default x86_64 machine anymore

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 16 Mar 2021 12:40:28 +0000
Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Tue, Mar 16, 2021 at 01:33:54PM +0100, Igor Mammedov wrote:
> > On Mon, 15 Mar 2021 15:05:26 -0700
> > Isaku Yamahata <isaku.yamahata@gmail.com> wrote:
> >   
> > > On Mon, Mar 15, 2021 at 05:58:04PM +0100,
> > > Reinoud Zandijk <reinoud@NetBSD.org> wrote:
> > >   
> > > > I think its better to revert this and fix Linux ;) or make it a selectable
> > > > feature as a workaround that's by default OFF :)    
> > > 
> > > Anyway here is a patch to flip the default.
> > > At the moment, this is compile-only tested to provide the change quickly
> > > and make discussion progress.
> > > 
> > > From 50deeed38832ceccfb68f78dd66de5a1741b2897 Mon Sep 17 00:00:00 2001
> > > Message-Id: <50deeed38832ceccfb68f78dd66de5a1741b2897.1615845421.git.isaku.yamahata@intel.com>
> > > From: Isaku Yamahata <isaku.yamahata@intel.com>
> > > Date: Mon, 15 Mar 2021 14:42:33 -0700
> > > Subject: [PATCH] ich9, piix4: flip default value for smm-compat
> > > 
> > > Make default value for smm-compat of ich9, piix4 true to keep old
> > > behavior.
> > > To get new (and more conformance to ACPI spec) behavior, explicitly
> > > set "-global ICH9-LPC.smm-compat=off" or
> > > "-global PIIX4_PM.smm-compat=off".  
> > 
> > I'm not sure we should do that,
> > it's fine for non-versioned/new machine type to change in incompatible way with old images,
> > it's the job of old versioned machines types to maintain compatibility.
> > It's of cause pain for users if they use are unable to boot old image
> > on newest machine type, but we never promised that and if we made such
> > promise we would never be able to fix bugs.  
> 
> If this incompatibility with Windows 10 is confirmed though, I don't
> think it is viable for QEMU to ship the default machine type with
> settings that break Windows 10.

Choice is Windows vs Linux kernel
the later behaves correctly (as spec dictates) and 'offending' commit
fixes QEMU deviation from spec. It might be hard to convince kernel
side to merge a hack for Windows sake that goes against spec.
As for Windows, if new install works fine then that's all fine,
users really should use version-ed machine types or instead of
pushing old broken 'features' to [new] default machine types.

> 
> 
> 
> Regards,
> Daniel