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[PATCH v2 10/13] x86/nSVM: Don't clear TLB_CONTROL on #VMEXIT
- To: xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: chunjie.zhu@xxxxxxxxxx
- Date: Sat, 10 Oct 2026 18:13:23 +0800
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- Delivery-date: Sat, 10 Oct 2026 10:16:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
From: Lin Liu <lin.liu01@xxxxxxxxxx>
nsvm_vmcb_prepare4vmexit() zeroes TLB_CONTROL in the L1-provided VMCB.
That VMCB is mapped writable, so the store lands in L1's memory and L1
sees a field it wrote come back as 0.
APM vol 2 rev 3.45 15.16.1 (p.550): "The VMRUN instruction reads, but
does not change, the value of the TLB_CONTROL field."
Fixes: 9a779e4fc161 ("Implement SVM specific part for Nested Virtualization")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Lin Liu <lin.liu01@xxxxxxxxxx>
---
xen/arch/x86/hvm/svm/nestedsvm.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c b/xen/arch/x86/hvm/svm/nestedsvm.c
index e1cb10e1de11..3b0afb828c91 100644
--- a/xen/arch/x86/hvm/svm/nestedsvm.c
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c
@@ -992,9 +992,6 @@ nsvm_vmcb_prepare4vmexit(struct vcpu *v, struct
cpu_user_regs *regs)
/* ASID */
/* vmcb_set_asid(ns_vmcb, vmcb_get_asid(n2vmcb)); */
- /* TLB control */
- ns_vmcb->tlb_control = 0;
-
/* Virtual Interrupts */
ns_vmcb->_vintr = n2vmcb->_vintr;
if ( !svm->ns_hostflags.fields.vintrmask )
--
2.34.1
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