x86/boot: Fix kexec booting failure in the SEV bit detection code
Commit 1958b5fc ("x86/boot: Add early boot support when running with SEV active") can occasionally cause system resets when kexec-ing a second kernel even if SEV is not active. That's because get_sev_encryption_bit() uses 32-bit rIP-relative addressing to read the value of enc_bit - a variable which caches a previously detected encryption bit position - but kexec may allocate the early boot code to a higher location, beyond the 32-bit addressing limit. In this case, garbage will be read and get_sev_encryption_bit() will return the wrong value, leading to accessing memory with the wrong encryption setting. Therefore, remove enc_bit, and thus get rid of the need to do 32-bit rIP-relative addressing in the first place. [ bp: massage commit message heavily. ] Fixes: 1958b5fc ("x86/boot: Add early boot support when running with SEV active") Suggested-by:Borislav Petkov <bp@suse.de> Signed-off-by:
Kairui Song <kasong@redhat.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Reviewed-by:
Tom Lendacky <thomas.lendacky@amd.com> Cc: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de Cc: mingo@redhat.com Cc: hpa@zytor.com Cc: brijesh.singh@amd.com Cc: kexec@lists.infradead.org Cc: dyoung@redhat.com Cc: bhe@redhat.com Cc: ghook@redhat.com Link: https://lkml.kernel.org/r/20180927123845.32052-1-kasong@redhat.com
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