Re: [Qemu-devel] [PATCH v2] pc: drop external DSDT loading

[Anthony Liguori <aliguori@us.ibm.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> On Mon, Aug 12, 2013 at 10:20:41AM -0500, Anthony Liguori wrote:
>> "Michael S. Tsirkin" <mst@redhat.com> writes:
>> 
>> > On Mon, Aug 12, 2013 at 09:01:44AM -0500, Anthony Liguori wrote:
>> >> This breaks migration and is unneeded with modern SeaBIOS.
>> >> 
>> >> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
>> >
>> > Hmm don't we want to keep it around for machine types
>> > 1.4.0 and 1.5.0?
>> 
>> Hrm, why?
>
> Well this modifies the contents of ROM which
> is loaded from FW CFG and isn't migrated, correct?
> If guest is migrated from 1.6 to 1.5
> while it is loading the ROM,
> it will likely get a corrupted table.

No, if you migrate from 1.6 to 1.5 the ROM is untouched.  ROMs aren't
migrated so it doesn't really matter.

If you migrate from 1.5 while reading the ROM contents, then badness can
ensue but that's already the case without this patch.

Regards,

Anthony Liguori

>
>
>> Regards,
>> 
>> Anthony Liguori
>> 
>> >
>> > By the way, copy stable as well?
>> > Loading it unconditonally is a cross
>> > version migration bug that we probably want to fix
>> > on stable branch - disabling for 1.3.0 and older.
>> >
>> >> ---
>> >> v1 -> v2
>> >>  - Still load external DSDT for q35
>> >> ---
>> >>  hw/i386/pc_piix.c | 1 -
>> >>  1 file changed, 1 deletion(-)
>> >> 
>> >> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>> >> index 95c45b8..311574a 100644
>> >> --- a/hw/i386/pc_piix.c
>> >> +++ b/hw/i386/pc_piix.c
>> >> @@ -103,7 +103,6 @@ static void pc_init1(MemoryRegion *system_memory,
>> >>                                OBJECT(icc_bridge), NULL);
>> >>  
>> >>      pc_cpus_init(cpu_model, icc_bridge);
>> >> -    pc_acpi_init("acpi-dsdt.aml");
>> >>  
>> >>      if (kvm_enabled() && kvmclock_enabled) {
>> >>          kvmclock_create();
>> >> -- 
>> >> 1.8.0