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[PATCH v1 24/28] x86/hvm: avic: ensure SVM AVIC is disabled with nested guest
- To: xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: dmukhin@xxxxxxxx
- Date: Wed, 4 Nov 2026 17:33:41 -0800
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- Cc: andrew.cooper3@xxxxxxxxxx, jason.andryuk@xxxxxxx, jbeulich@xxxxxxxx, roger@xxxxxxxxxxxxxx, teddy.astie@xxxxxxxxxx, dmukhin@xxxxxxx, Denis Mukhin <dmukhin@xxxxxxxx>
- Delivery-date: Thu, 05 Nov 2026 01:35:18 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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From: Denis Mukhin <dmukhin@xxxxxxxx>
AVIC in nested virtualization environment is not supported as of yet.
Ensure there will be no problems in any production environments if AVIC
got enabled in nested guest by short-circuiting logic in
svm_avic_create_vmcb().
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
xen/arch/x86/hvm/svm/avic.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/xen/arch/x86/hvm/svm/avic.c b/xen/arch/x86/hvm/svm/avic.c
index 37a857f28d14..e19489bd485c 100644
--- a/xen/arch/x86/hvm/svm/avic.c
+++ b/xen/arch/x86/hvm/svm/avic.c
@@ -4,6 +4,7 @@
*/
#include <asm/hvm/emulate.h>
+#include <asm/hvm/nestedhvm.h>
#include <asm/msr.h>
#include <asm/p2m.h>
#include <xen/param.h>
@@ -170,6 +171,14 @@ static bool avic_vcpu_supported(struct vcpu *v)
return false;
}
+ if ( nestedhvm_enabled(d) && nestedhvm_vcpu_in_guestmode(v) )
+ {
+ gprintk(XENLOG_WARNING,
+ "%pv: AVIC: nested guest is not supported\n",
+ v);
+ return false;
+ }
+
id = GET_xAPIC_ID(vlapic_reg_read(v, APIC_ID));
if ( id > AVIC_MAX_PHYSICAL_ID )
{
--
2.55.0
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