[PATCH] x86/nSVM: Don't clear TLB_CONTROL on #VMEXIT

[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 a8b15d6eae..1ac2e57b3b 100644
--- a/xen/arch/x86/hvm/svm/nestedsvm.c
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c
@@ -991,9 +991,6 @@ 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 )
-- 
2.52.0