RDMSR in the trampoline code overrides EDX, but we use the register to
indicate if 5-level paging has to enabled. It leads to failure to boot
on a 5-level paging machine.
Preserve EDX on the stack while we are dealing with EFER.
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Fixes: b677dfae5aa1 ("x86/boot/compressed/64: Set EFER.LME=1 in 32-bit
trampoline before returning to long mode")
Reported-by: Kyle D Pelton <kyle.d.pel...@intel.com>
Cc: Wei Huang <w...@redhat.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 f105ae8651c9..f62e347862cc 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 */
--
2.20.1
