[xen master] VMX: don't run with CR4.VMXE set when VMX could not be enabled

[patchbot@xxxxxxx]

commit 04f5be6e1d3a6ea3f45b56c2af88c50cacd108a5
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Feb 25 08:44:32 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Feb 25 08:44:32 2025 +0100

    VMX: don't run with CR4.VMXE set when VMX could not be enabled
    
    While generally benign, doing so is still at best misleading.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index eee1d4b47a..3728d2cd0d 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2987,14 +2987,18 @@ static bool __init has_if_pschange_mc(void)
 
 const struct hvm_function_table * __init start_vmx(void)
 {
-    set_in_cr4(X86_CR4_VMXE);
+    write_cr4(read_cr4() | X86_CR4_VMXE);
 
     if ( vmx_vmcs_init() )
     {
+        write_cr4(read_cr4() & ~X86_CR4_VMXE);
         printk("VMX: failed to initialise.\n");
         return NULL;
     }
 
+    /* Arrange for APs to have CR4.VMXE set early on. */
+    set_in_cr4(X86_CR4_VMXE);
+
     vmx_function_table.caps.singlestep = cpu_has_monitor_trap_flag;
 
     if ( cpu_has_vmx_dt_exiting )
--
generated by git-patchbot for /home/xen/git/xen.git#master