[xen master] x86/hvm: Disable cross-vendor handling in #UD handler

[patchbot@xxxxxxx]

commit e39e473188ccc60ed10b444dff0cc73648d4e7ad
Author:     Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
AuthorDate: Thu Mar 12 12:21:11 2026 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Apr 9 08:22:52 2026 +0200

    x86/hvm: Disable cross-vendor handling in #UD handler
    
    Remove cross-vendor support now that VMs can no longer have a different
    vendor than the host.
    
    No functional change intended.
    
    Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c     | 19 ++-----------------
 xen/arch/x86/hvm/svm/svm.c |  3 +--
 xen/arch/x86/hvm/vmx/vmx.c |  3 +--
 3 files changed, 4 insertions(+), 21 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 11e9b2bc88..4a81afce02 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3829,28 +3829,13 @@ int hvm_descriptor_access_intercept(uint64_t exit_info,
     return X86EMUL_OKAY;
 }
 
-static bool cf_check is_cross_vendor(
-    const struct x86_emulate_state *state, const struct x86_emulate_ctxt *ctxt)
-{
-    switch ( ctxt->opcode )
-    {
-    case X86EMUL_OPC(0x0f, 0x05): /* syscall */
-    case X86EMUL_OPC(0x0f, 0x34): /* sysenter */
-    case X86EMUL_OPC(0x0f, 0x35): /* sysexit */
-        return true;
-    }
-
-    return false;
-}
-
 void hvm_ud_intercept(struct cpu_user_regs *regs)
 {
     struct vcpu *cur = current;
-    bool should_emulate =
-        cur->domain->arch.cpuid->x86_vendor != boot_cpu_data.x86_vendor;
+    bool should_emulate = false;
     struct hvm_emulate_ctxt ctxt;
 
-    hvm_emulate_init_once(&ctxt, opt_hvm_fep ? NULL : is_cross_vendor, regs);
+    hvm_emulate_init_once(&ctxt, NULL, regs);
 
     if ( opt_hvm_fep )
     {
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 2546705d24..d4502d3c0f 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -543,8 +543,7 @@ static void cf_check svm_cpuid_policy_changed(struct vcpu 
*v)
     const struct cpu_policy *cp = v->domain->arch.cpu_policy;
     u32 bitmap = vmcb_get_exception_intercepts(vmcb);
 
-    if ( opt_hvm_fep ||
-         (v->domain->arch.cpuid->x86_vendor != boot_cpu_data.x86_vendor) )
+    if ( opt_hvm_fep )
         bitmap |= (1U << X86_EXC_UD);
     else
         bitmap &= ~(1U << X86_EXC_UD);
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 03daf2f52b..269ca56433 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -802,8 +802,7 @@ static void cf_check vmx_cpuid_policy_changed(struct vcpu 
*v)
     const struct cpu_policy *cp = v->domain->arch.cpu_policy;
     int rc = 0;
 
-    if ( opt_hvm_fep ||
-         (v->domain->arch.cpuid->x86_vendor != boot_cpu_data.x86_vendor) )
+    if ( opt_hvm_fep )
         v->arch.hvm.vmx.exception_bitmap |= (1U << X86_EXC_UD);
     else
         v->arch.hvm.vmx.exception_bitmap &= ~(1U << X86_EXC_UD);
--
generated by git-patchbot for /home/xen/git/xen.git#master