Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory

Dionna Amalie Glaze
2022-07-19T18:29:46Z

> > > I think we should make it obvious from a kernel image if it supports
> > > unaccepted memory (with UTS_VERSION or other way).
> > >
>
> Something I didn't address in my previous email: how would the UEFI
> know where the kernel is to parse this UTS_VERSION out when it's
> booting a bootloader before Linux gets booted?
>

How about instead of the limited resource of UTS_VERSION, we add a
SETUP_BOOT_FEATURES enum for setup_data in the boot header? That would
be easier to parse out and more extensible in the future.
https://www.kernel.org/doc/html/latest/x86/boot.html?highlight=boot

This can contain a bitmap of a number of features that we currently
need manual tagging for, such as SEV guest support, SEV-SNP guest
support, TDX guest support, and (CONFIG_UNACCEPTED_MEMORY, TDX) or
(CONFIG_UNACCEPTED_MEMORY, SEV-SNP).
The VMM, UEFI, or boot loader can read these from the images/kernels
and have the appropriate behavior.

--
-Dionna Glaze, PhD (she/her)