x86 svm: Disable intercepting CR3 writes when nested paging is enabled

This patch disables intercepting CR3 writes when nested paging is
enabled. For applications which cause excessive CR3 accesses, the
patch can increase their performance.

Signed-off-by: Wei Huang <wei.huang2@amd.com>

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 1cef8be5cb4266e00f8c0fd203a04e7bfdc249f0..767803a7daf04a106bee0681380cf4c174077147 100644 (file)
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1299,6 +1299,9 @@ asmlinkage void svm_vmexit_handler(struct cpu_user_regs *regs)
     eventinj_t eventinj;
     int inst_len, rc;
 
+    if ( paging_mode_hap(v->domain) )
+        v->arch.hvm_vcpu.guest_cr[3] = v->arch.hvm_vcpu.hw_cr[3] = vmcb->cr3;
+
     /*
      * Before doing anything else, we need to sync up the VLAPIC's TPR with
      * SVM's vTPR. It's OK if the guest doesn't touch CR8 (e.g. 32-bit Windows)

diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
index d83fdc185aa60d3f09443c18a705258e23e2e16d..0a56132dd0256906542da9156b83b8c130ec7381 100644 (file)
--- a/xen/arch/x86/hvm/svm/vmcb.c
+++ b/xen/arch/x86/hvm/svm/vmcb.c
@@ -235,11 +235,8 @@ static int construct_vmcb(struct vcpu *v)
         vmcb->g_pat = 0x0007040600070406ULL; /* guest PAT */
         vmcb->h_cr3 = pagetable_get_paddr(v->domain->arch.phys_table);
 
-        /*
-         * No point in intercepting CR3 reads, because the hardware will return
-         * the guest version anyway.
-         */
-        vmcb->cr_intercepts &= ~CR_INTERCEPT_CR3_READ;
+        /* No point in intercepting CR3 reads/writes. */
+        vmcb->cr_intercepts &= ~(CR_INTERCEPT_CR3_READ|CR_INTERCEPT_CR3_WRITE);
 
         /*
          * No point in intercepting INVLPG if we don't have shadow pagetables