[edk2-devel] [RFC PATCH] OvmfPkg/OvmfXen: set PcdAcpiS3Enable at initialization

[Anthony PERARD via groups.io]

On Wed, Jul 21, 2021 at 02:56:46PM +0800, Gary Lin wrote:
> BTW, it seems to me that QEMU fwcfg is only used for Xen Direct Kernel
> Boot. However, per xl.cfg manpage, it's possible to turn on or off S3
> support by setting "acpi_s3" in xl.cfg, but PcdAcpiS3Enable wasn't set
> in the current OvmfXen implementation. Just wonder how xl passes the S3
> support bit to OvmfXen.

It doesn't. "acpi_s3" doesn't have any control over PcdAcpiS3Enable, and
doesn't have any control over QEMU, so QEMU would probably always say S3
is available.

What happen when "acpi_s3" is set or not is:
    - the value is stored in xenstore
    - hvmloader (which runs before OVMF) read the xenstore value and
      adds the appropriate ACPI SSDT table to allow S3.

Cheers,

-- 
Anthony PERARD


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