diff mbox series

[PATCHv7,05/16] x86/kexec: Keep CR4.MCE set during kexec for TDX guest

Message ID 20240212104448.2589568-6-kirill.shutemov@linux.intel.com
State New
Headers
Series x86/tdx: Add kexec support |

Commit Message

Kirill A. Shutemov Feb. 12, 2024, 10:44 a.m. UTC 
  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.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/kernel/relocate_kernel_64.S | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Thomas Gleixner Feb. 22, 2024, 10:04 p.m. UTC | #1 
On Mon, Feb 12 2024 at 12:44, Kirill A. Shutemov wrote:

> 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.shutemov@linux.intel.com>
> Reviewed-by: Kai Huang <kai.huang@intel.com>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
diff mbox series

Patch

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