From: Ashish Kalra Date: Thu, 1 Aug 2024 19:14:17 +0000 (+0000) Subject: x86/boot: Skip video memory access in the decompressor for SEV-ES/SNP X-Git-Tag: v6.13-rc1~183^2~3 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f30470c190c2f4776e0baeba1f53fd8dd3820394;p=thirdparty%2Fkernel%2Flinux.git x86/boot: Skip video memory access in the decompressor for SEV-ES/SNP 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) Suggested-by: Thomas Lendacky Signed-off-by: Ashish Kalra Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Link: https://lore.kernel.org/r/8a55ea86524c686e575d273311acbe57ce8cee23.1722520012.git.ashish.kalra@amd.com --- diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 04a35b2c26e9b..0d37420cad025 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -385,6 +385,19 @@ static void parse_mem_encrypt(struct setup_header *hdr) hdr->xloadflags |= XLF_MEM_ENCRYPTION; } +static void early_sev_detect(void) +{ + /* + * Accessing video memory causes guest termination because + * the boot stage2 #VC handler of SEV-ES/SNP guests does not + * support MMIO handling and 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. + */ + if (sev_status & MSR_AMD64_SEV_ES_ENABLED) + lines = cols = 0; +} + /* * The compressed kernel image (ZO), has been moved so that its position * is against the end of the buffer used to hold the uncompressed kernel @@ -440,6 +453,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output) */ early_tdx_detect(); + early_sev_detect(); + console_init(); /*