[PATCH v9 2/3] x86/boot: Skip video memory access in the decompressor for SEV-ES/SNP

[Tom Lendacky]

On 6/20/24 17:23, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra at amd.com>
> 
> Accessing guest video memory/RAM in the decompressor causes guest
> termination as the boot stage2 #VC handler for SEV-ES/SNP systems does
> not support MMIO handling.
> 
> This issue is observed during a SEV-ES/SNP guest kexec as kexec -c adds
> screen_info to the boot parameters passed to the second kernel, which
> causes console output to be dumped to both video and serial.
> 
> As the decompressor output gets cleared really fast, it is preferable to
> get the console output only on serial, hence, skip accessing the video
> RAM during decompressor stage to prevent guest termination.
> 
> Serial console output during decompressor stage works as boot stage2 #VC
> handler already supports handling port I/O.
> 
>   [ bp: Massage. ]
> 
> Suggested-by: Borislav Petkov (AMD) <bp at alien8.de>
> Suggested-by: Thomas Lendacy <thomas.lendacky at amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra at amd.com>
> Signed-off-by: Borislav Petkov (AMD) <bp at alien8.de>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy at linux.intel.com>

Reviewed-by: Tom Lendacky <thomas.lendacky at amd.com>

> ---
>  arch/x86/boot/compressed/misc.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>