Re: [Qemu-devel] [seabios PATCH 1/2] seabios: build RSDT from XSDT

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Michael S. Tsirkin" <mst@redhat.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: seabios@seabios.org, "Kevin O'Connor" <kevin@koconnor.net>, qemu-devel@nongnu.org, lersek@redhat.com,
> lists@philjordan.eu, imammedo@redhat.com, phil@philjordan.eu, programmingkidx@gmail.com, kraxel@redhat.com
> Sent: Wednesday, July 26, 2017 10:05:03 PM
> Subject: Re: [seabios PATCH 1/2] seabios: build RSDT from XSDT
> 
> On Wed, Jul 26, 2017 at 11:42:34AM +0200, Paolo Bonzini wrote:
> > Old operating systems would like to have a rev1 (ACPI 1.0) FADT, but
> > new operating systems would like to have rev3 (ACPI 2.0).
> > 
> > Since old operating systems do not know about XSDTs, the
> > solution is to point the RSDT to a rev1 FADT and the XSDT to a
> > rev3 FADT.
> > 
> > But, edk2 is not able to handle QEMU providing two FADTs and barfs when
> > it sees the second; edk2 subscribes to the view that the platform code
> > (meaning not only OVMF, but transitively QEMU's ACPI table builder)
> > should not handle such hacks; it's common edk2 code that should handle
> > FADT rev1 vs. rev3 and RSDT vs. XSDT.
> 
> What exactly does it do wrt RSDT?

It ignores the one produced by QEMU and builds it from scratch.  Same
for RSDP and XSDT.

Paolo