[ Upstream commit 45b13b424faafb81c8c44541f093a682fdabdefc ]
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 kyle.d.pelton@intel.com Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Borislav Petkov bp@suse.de Cc: dave.hansen@linux.intel.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Wei Huang wei@redhat.com Cc: x86-ml x86@kernel.org Link: https://lkml.kernel.org/r/20190206115253.1907-1-kirill.shutemov@linux.intel.... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 */