diff mbox series

[v2,62/70] x86/alternatives: Clear CR4.CET when clearing CR0.WP

Message ID 20220214125127.17985-63-andrew.cooper3@citrix.com (mailing list archive)
State New, archived
Headers show
Series x86: Support for CET Indirect Branch Tracking | expand

Commit Message

Andrew Cooper Feb. 14, 2022, 12:51 p.m. UTC 
This allows us to have CET active much earlier in boot.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/alternative.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index 436047abe021..ec24692e9595 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -333,9 +333,13 @@  static int __init cf_check nmi_apply_alternatives(
      */
     if ( !(alt_done & alt_todo) )
     {
-        unsigned long cr0;
+        unsigned long cr0, cr4;
 
         cr0 = read_cr0();
+        cr4 = read_cr4();
+
+        if ( cr4 & X86_CR4_CET )
+            write_cr4(cr4 & ~X86_CR4_CET);
 
         /* Disable WP to allow patching read-only pages. */
         write_cr0(cr0 & ~X86_CR0_WP);
@@ -345,6 +349,9 @@  static int __init cf_check nmi_apply_alternatives(
 
         write_cr0(cr0);
 
+        if ( cr4 & X86_CR4_CET )
+            write_cr4(cr4);
+
         alt_done |= alt_todo;
     }