x86/sev: Create snp_shutdown()

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After SNP_SHUTDOWN, two things should be done:

1. clear the RMP table
2. disable MFDM to prevent the FW_WARN in k8_check_syscfg_dram_mod_en() in
   the event of a kexec

Create and export to the CCP driver a function that does them.

Also change the MFDM helper to allow for disabling the bit, since the SNP x86
shutdown path needs to disable MFDM.

The comment for k8_check_syscfg_dram_mod_en() notes, the "BIOS" is supposed
clear it, or the kernel in the case of module unload and shutdown followed by
kexec.

Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://patch.msgid.link/20260324161301.1353976-4-tycho@kernel.org

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This commit is contained in:

Tycho Andersen (AMD) 2026-03-24 10:12:57 -06:00 • committed by Borislav Petkov (AMD)

parent ca2ca373ec

commit b65546b14d

2 changed files with 21 additions and 3 deletions

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2

arch/x86/include/asm/sev.h

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22

arch/x86/virt/svm/sev.c

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