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

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Mar 15, 2021 at 05:58:04PM +0100, Reinoud Zandijk wrote:
> Hi,
> 
> with the introduction of the following patch from 17th of February, Win10
> won't boot anymore without explicitly setting the machine to be 5.2 compatible
> like pc-1440fx-5.2. The default 6.0 will cause it to panic and gives as reason
> only "ACPI error".
> 
> It might work to counter a bug in Linux but this is not the place to do the
> patch. The BSDs don't care and will boot fine with full ACPI regardless of the
> machine chosen. Windows 10 however DOES care and gets confused.
> 
> I think its better to revert this and fix Linux ;) or make it a selectable
> feature as a workaround that's by default OFF :)

I'm copying the people involved in creating/reviewing the commit you
mention below.

I've also added this regression to the 6.0 issues list, since being
able to boot current Windows guests with the default machine type
should be considered a release blocker IMHO.

   https://wiki.qemu.org/Planning/6.0#Not_fixed_yet

> 
> With regards,
> Reinoud
> 
> 
> The patch concerned is:
> 
> commit 6be8cf56bc8bda2ed9a070bdb04446191f31acc9
> Author: Isaku Yamahata <isaku.yamahata@intel.com>
> Date:   Wed Feb 17 21:51:12 2021 -0800
> 
>     acpi/core: always set SCI_EN when SMM isn't supported
>     
>     If SMM is not supported, ACPI fixed hardware doesn't support
>     legacy-mode. ACPI-only platform. Where SCI_EN in PM1_CNT register is
>     always set.
>     The bit tells OS legacy mode(SCI_EN cleared) or ACPI mode(SCI_EN set).
>     
>     With the next patch (setting fadt.smi_cmd = 0 when smm isn't enabled),
>     guest Linux tries to switch to ACPI mode, finds smi_cmd = 0, and then
>     fails to initialize acpi subsystem. This patch proactively fixes it.
>     
>     This patch changes guest ABI. To keep compatibility, use
>     "smm-compat" introduced by earlier patch. If the property is true,
>     disable new behavior.
>     
>     ACPI spec 4.8.10.1 PM1 Event Grouping
>     PM1 Eanble Registers
>     > For ACPI-only platforms (where SCI_EN is always set)
>     
>     Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>     Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
>     Message-Id:
> <500f62081626997e46f96377393d3662211763a8.1613615732.git.isaku.yamahata@intel.com>
>     Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>     Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
>  hw/acpi/core.c         | 11 ++++++++++-
>  hw/acpi/ich9.c         |  2 +-
>  hw/acpi/piix4.c        |  3 ++-
>  hw/core/machine.c      |  5 ++++-
>  hw/isa/vt82c686.c      |  2 +-
>  include/hw/acpi/acpi.h |  4 +++-
>  6 files changed, 21 insertions(+), 6 deletions(-)
> 
> 



Regards,
Daniel
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