From 48cdc15a424f9fadad7f9aed00e7dc8ef16a2196 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Mon, 1 Nov 2021 10:17:59 +0000 Subject: [PATCH] x86/alternatives: Clear CR4.CET when clearing CR0.WP This allows us to have CET active much earlier in boot. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/arch/x86/alternative.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c index 436047abe0..ec24692e95 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; } -- 2.30.2