TDX guests are not allowed to clear CR4.MCE. Attempt to clear it leads
to #VE.
Use alternatives to keep the flag during kexec for TDX guests.
The change doesn't affect non-TDX-guest environments.
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Reviewed-by: Kai Huang <kai.hu...@intel.com>
---
arch/x86/kernel/relocate_kernel_64.S | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/relocate_kernel_64.S
b/arch/x86/kernel/relocate_kernel_64.S
index 56cab1bb25f5..e144bcf60cbe 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -5,6 +5,8 @@
*/
#include <linux/linkage.h>
+#include <linux/stringify.h>
+#include <asm/alternative.h>
#include <asm/page_types.h>
#include <asm/kexec.h>
#include <asm/processor-flags.h>
@@ -145,12 +147,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
* Set cr4 to a known state:
* - physical address extension enabled
* - 5-level paging, if it was enabled before
+ * - Machine check exception on TDX guest. Clearing MCE is not allowed
+ * in TDX guests.
*/
movl $X86_CR4_PAE, %eax
testq $X86_CR4_LA57, %r13
jz 1f
orl $X86_CR4_LA57, %eax
1:
+ ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %eax),
X86_FEATURE_TDX_GUEST
movq %rax, %cr4
jmp 1f
--
2.41.0
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