On 4/4/24 4:11 PM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.ka...@amd.com>
>
> Accessing guest video memory/RAM during kernel decompressor
> causes guest termination as boot stage2 #VC handler for
> SEV-ES/SNP systems does not support MMIO handling.
>
> This issue is observed with SEV-ES/SNP guest kexec as
> kexec -c adds screen_info to the boot parameters
> passed to the kexec 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 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.
>
> Suggested-by: Thomas Lendacy <thomas.lenda...@amd.com>
> Signed-off-by: Ashish Kalra <ashish.ka...@amd.com>
> ---
Looks good to me.
Reviewed-by: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppusw...@linux.intel.com>
> arch/x86/boot/compressed/misc.c | 6 ++++--
> arch/x86/boot/compressed/misc.h | 1 +
> 2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index b70e4a21c15f..47b4db200e1f 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -427,8 +427,10 @@ asmlinkage __visible void *extract_kernel(void *rmode,
> unsigned char *output)
> vidport = 0x3d4;
> }
>
> - lines = boot_params_ptr->screen_info.orig_video_lines;
> - cols = boot_params_ptr->screen_info.orig_video_cols;
> + if (!sev_es_enabled()) {
> + lines = boot_params_ptr->screen_info.orig_video_lines;
> + cols = boot_params_ptr->screen_info.orig_video_cols;
> + }
>
> init_default_io_ops();
>
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index b353a7be380c..3c12ca987554 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -37,6 +37,7 @@
> #include <asm/desc_defs.h>
>
> #include "tdx.h"
> +#include "sev.h"
>
> #define BOOT_CTYPE_H
> #include <linux/acpi.h>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
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