[ 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 <[email protected]>
Signed-off-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Wei Huang <[email protected]>
Cc: x86-ml <[email protected]>
Link:
https://lkml.kernel.org/r/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
---
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
