Virtualization - Feb 2021 - [PATCH 0/7] x86/seves: Support 32-bit boot path and other updates

On Wed, Feb 10, 2021 at 11:21:28AM +0100, Joerg Roedel
wrote:
> From: Joerg Roedel <jroedel at suse.de>
> 
> Hi,
> 
> these patches add support for the 32-bit boot in the decompressor
> code. This is needed to boot an SEV-ES guest on some firmware and grub
> versions. The patches also add the necessary CPUID sanity checks and a
Could you expand a bit please?

What GRUB versions are we talking about (CC-ing Daniel Kiper, who owns
GRUB).

By 'some firmware' we talking SeaBIOS?
> 32-bit version of the C-bit check.
> 
> Other updates included here:
> 
> 	1. Add code to shut down exception handling in the
> 	   decompressor code before jumping to the real kernel.
> 	   Once in the real kernel it is not safe anymore to jump
> 	   back to the decompressor code via exceptions.
> 
> 	2. Replace open-coded hlt loops with proper calls to
> 	   sev_es_terminate().
> 
> Please review.
> 
> Thanks,
> 
> 	Joerg
> 
> Joerg Roedel (7):
>   x86/boot/compressed/64: Cleanup exception handling before booting
>     kernel
>   x86/boot/compressed/64: Reload CS in startup_32
>   x86/boot/compressed/64: Setup IDT in startup_32 boot path
>   x86/boot/compressed/64: Add 32-bit boot #VC handler
>   x86/boot/compressed/64: Add CPUID sanity check to 32-bit boot-path
>   x86/boot/compressed/64: Check SEV encryption in 32-bit boot-path
>   x86/sev-es: Replace open-coded hlt-loops with sev_es_terminate()
> 
>  arch/x86/boot/compressed/head_64.S     | 168 ++++++++++++++++++++++++-
>  arch/x86/boot/compressed/idt_64.c      |  14 +++
>  arch/x86/boot/compressed/mem_encrypt.S | 114 ++++++++++++++++-
>  arch/x86/boot/compressed/misc.c        |   7 +-
>  arch/x86/boot/compressed/misc.h        |   6 +
>  arch/x86/boot/compressed/sev-es.c      |  12 +-
>  arch/x86/kernel/sev-es-shared.c        |  10 +-
>  7 files changed, 307 insertions(+), 24 deletions(-)
> 
> -- 
> 2.30.0
>

Hi Konrad,

On Wed, Feb 10, 2021 at 09:58:35AM -0500, Konrad Rzeszutek Wilk
wrote:
> What GRUB versions are we talking about (CC-ing Daniel Kiper, who owns
> GRUB).
I think this was about 32-bit GRUB builds used by distributions. I
personally tested it with a kernel which has EFI support disabled, in
this case the OVMF firmware will also boot into the startup_32 boot
path.
> By 'some firmware' we talking SeaBIOS?
No, SeaBIOS is not supported for SEV-ES, only OVMF has handling for #VC
so far.

Regards,

	Joerg