From 45b13b424faafb81c8c44541f093a682fdabdefc Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Wed, 6 Feb 2019 14:52:53 +0300 Subject: [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting RDMSR in the trampoline code overwrites EDX but that register is used to indicate whether 5-level paging has to be enabled and if clobbered, leads to failure to boot on a 5-level paging machine. Preserve EDX on the stack while we are dealing with EFER. Fixes: b677dfae5aa1 ("x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode") Reported-by: Kyle D Pelton Signed-off-by: Kirill A. Shutemov Signed-off-by: Borislav Petkov Cc: dave.hansen@linux.intel.com Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Wei Huang Cc: x86-ml Link: https://lkml.kernel.org/r/20190206115253.1907-1-kirill.shutemov@linux.intel.com --- arch/x86/boot/compressed/head_64.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index f105ae8..f62e3478 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -602,10 +602,12 @@ ENTRY(trampoline_32bit_src) 3: /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */ pushl %ecx + pushl %edx movl $MSR_EFER, %ecx rdmsr btsl $_EFER_LME, %eax wrmsr + popl %edx popl %ecx /* Enable PAE and LA57 (if required) paging modes */ -- 2.7.4