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[Xen-devel] Not call paging_update_cr3(v) when guest reads from CR3?

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Subject: [Xen-devel] Not call paging_update_cr3(v) when guest reads from CR3?
From: "Li, Xin B" <xin.b.li@xxxxxxxxx>
Date: Wed, 11 Apr 2007 23:57:41 +0800
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Thread-topic: Not call paging_update_cr3(v) when guest reads from CR3?
Hi Tim, 
I think it's not necessary to call paging_update_cr3(v) when guest reads
from CR3, am I right?

diff -r 38204c93428e xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c        Wed Apr 11 16:08:35 2007 +0100
+++ b/xen/arch/x86/hvm/vmx/vmx.c        Wed Apr 11 22:27:35 2007 +0800
@@ -2103,16 +2103,14 @@ static int mov_to_cr(int gp, int cr, str
          * We make a new one if the shadow does not exist.
-        if (value == v->arch.hvm_vmx.cpu_cr3) {
+        if ( value == v->arch.hvm_vmx.cpu_cr3 ) {
              * This is simple TLB flush, implying the guest has
              * removed some translation or changed page attributes.
-             * We simply invalidate the shadow.
             mfn = get_mfn_from_gpfn(value >> PAGE_SHIFT);
             if (mfn != pagetable_get_pfn(v->arch.guest_table))
                 goto bad_cr3;
-            paging_update_cr3(v);
         } else {
              * If different, make a shadow. Check if the PDBR is valid

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