[PATCH] nestedsvm: fix VMEXIT emulation

[PATCH] nestedsvm: fix VMEXIT emulation

[Christoph Egger]

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Values in regs can be newer than those in the shadow
vmcb (e.g. due to an instruction emulation right before).
So use the values from regs.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>


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diff -r 6b73078a4403 xen/arch/x86/hvm/svm/nestedsvm.c
--- a/xen/arch/x86/hvm/svm/nestedsvm.c	Fri Oct 12 14:38:20 2012 +0200
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c	Wed Oct 17 09:19:05 2012 +0200
@@ -990,7 +999,7 @@ nsvm_vmcb_guest_intercepts_trap(struct v
 }
 
 static int
-nsvm_vmcb_prepare4vmexit(struct vcpu *v)
+nsvm_vmcb_prepare4vmexit(struct vcpu *v, struct cpu_user_regs *regs)
 {
     struct nestedvcpu *nv = &vcpu_nestedhvm(v);
     struct nestedsvm *svm = &vcpu_nestedsvm(v);
@@ -1114,17 +1123,22 @@ nsvm_vmcb_prepare4vmexit(struct vcpu *v)
     ns_vmcb->_dr7 = n2vmcb->_dr7;
     ns_vmcb->_dr6 = n2vmcb->_dr6;
 
+    /* Restore registers from regs as those values
+     * can be newer than in n2vmcb (e.g. due to an
+     * instruction emulation right before).
+     */
+
     /* RFLAGS */
-    ns_vmcb->rflags = n2vmcb->rflags;
+    ns_vmcb->rflags = n2vmcb->rflags = regs->rflags;
 
     /* RIP */
-    ns_vmcb->rip = n2vmcb->rip;
+    ns_vmcb->rip = n2vmcb->rip = regs->rip;
 
     /* RSP */
-    ns_vmcb->rsp = n2vmcb->rsp;
+    ns_vmcb->rsp = n2vmcb->rsp = regs->rsp;
 
     /* RAX */
-    ns_vmcb->rax = n2vmcb->rax;
+    ns_vmcb->rax = n2vmcb->rax = regs->rax;
 
     /* Keep the l2 guest values of the fs, gs, ldtr, tr, kerngsbase,
      * star, lstar, cstar, sfmask, sysenter_cs, sysenter_esp,
@@ -1358,7 +1372,7 @@ nestedsvm_vmexit_n2n1(struct vcpu *v, st
     ASSERT(vcpu_nestedhvm(v).nv_vmswitch_in_progress);
     ASSERT(nestedhvm_vcpu_in_guestmode(v));
 
-    rc = nsvm_vmcb_prepare4vmexit(v);
+    rc = nsvm_vmcb_prepare4vmexit(v, regs);
     if (rc)
         ret = NESTEDHVM_VMEXIT_ERROR;
 

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Re: [PATCH] nestedsvm: fix VMEXIT emulation

[Tim Deegan]

At 11:08 +0200 on 17 Oct (1350472115), Christoph Egger wrote:
> 
> Values in regs can be newer than those in the shadow
> vmcb (e.g. due to an instruction emulation right before).
> So use the values from regs.
> 
> Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>

Acked-by: Tim Deegan <tim@xen.org>


Content-Description: xen_nh_vmexit.diff
> diff -r 6b73078a4403 xen/arch/x86/hvm/svm/nestedsvm.c
> --- a/xen/arch/x86/hvm/svm/nestedsvm.c	Fri Oct 12 14:38:20 2012 +0200
> +++ b/xen/arch/x86/hvm/svm/nestedsvm.c	Wed Oct 17 09:19:05 2012 +0200
> @@ -990,7 +999,7 @@ nsvm_vmcb_guest_intercepts_trap(struct v
>  }
>  
>  static int
> -nsvm_vmcb_prepare4vmexit(struct vcpu *v)
> +nsvm_vmcb_prepare4vmexit(struct vcpu *v, struct cpu_user_regs *regs)
>  {
>      struct nestedvcpu *nv = &vcpu_nestedhvm(v);
>      struct nestedsvm *svm = &vcpu_nestedsvm(v);
> @@ -1114,17 +1123,22 @@ nsvm_vmcb_prepare4vmexit(struct vcpu *v)
>      ns_vmcb->_dr7 = n2vmcb->_dr7;
>      ns_vmcb->_dr6 = n2vmcb->_dr6;
>  
> +    /* Restore registers from regs as those values
> +     * can be newer than in n2vmcb (e.g. due to an
> +     * instruction emulation right before).
> +     */
> +
>      /* RFLAGS */
> -    ns_vmcb->rflags = n2vmcb->rflags;
> +    ns_vmcb->rflags = n2vmcb->rflags = regs->rflags;
>  
>      /* RIP */
> -    ns_vmcb->rip = n2vmcb->rip;
> +    ns_vmcb->rip = n2vmcb->rip = regs->rip;
>  
>      /* RSP */
> -    ns_vmcb->rsp = n2vmcb->rsp;
> +    ns_vmcb->rsp = n2vmcb->rsp = regs->rsp;
>  
>      /* RAX */
> -    ns_vmcb->rax = n2vmcb->rax;
> +    ns_vmcb->rax = n2vmcb->rax = regs->rax;
>  
>      /* Keep the l2 guest values of the fs, gs, ldtr, tr, kerngsbase,
>       * star, lstar, cstar, sfmask, sysenter_cs, sysenter_esp,
> @@ -1358,7 +1372,7 @@ nestedsvm_vmexit_n2n1(struct vcpu *v, st
>      ASSERT(vcpu_nestedhvm(v).nv_vmswitch_in_progress);
>      ASSERT(nestedhvm_vcpu_in_guestmode(v));
>  
> -    rc = nsvm_vmcb_prepare4vmexit(v);
> +    rc = nsvm_vmcb_prepare4vmexit(v, regs);
>      if (rc)
>          ret = NESTEDHVM_VMEXIT_ERROR;
>  

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