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Re: [Xen-devel] [PATCH v2 2/4] x86/pvh: Set 32b PVH guest mode in XEN_DOMCTL_set_address_size



On 07/07/2015 05:15 AM, Jan Beulich wrote:
On 29.06.15 at 22:21, <boris.ostrovsky@xxxxxxxxxx> wrote:
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -377,25 +377,25 @@ int switch_compat(struct domain *d)
      struct vcpu *v;
      int rc;
- if ( is_pvh_domain(d) )
-    {
-        printk(XENLOG_G_INFO
-               "Xen currently does not support 32bit PVH guests\n");
-        return -EINVAL;
-    }
-
      if ( !may_switch_mode(d) )
          return -EACCES;
      if ( has_32bit_shinfo(d) )
          return 0;
- d->arch.is_32bit_pv = d->arch.has_32bit_shinfo = 1;
+    d->arch.has_32bit_shinfo = 1;
+    if ( is_pv_domain(d) )
+        d->arch.is_32bit_pv = 1;
for_each_vcpu( d, v )
      {
          rc = setup_compat_arg_xlat(v);
          if ( !rc )
-            rc = setup_compat_l4(v);
+        {
+            if ( !is_pvh_domain(d) )
+                rc = setup_compat_l4(v);
+            else
+                rc = hvm_set_mode(v, 4);
+        }
          if ( rc )
              goto undo_and_fail;
      }
@@ -410,7 +410,7 @@ int switch_compat(struct domain *d)
      {
          free_compat_arg_xlat(v);
- if ( !pagetable_is_null(v->arch.guest_table) )
+        if ( !is_pvh_domain(d) && !pagetable_is_null(v->arch.guest_table) )
              release_compat_l4(v);
      }
And no respective change to switch_native()?




@@ -6491,6 +6490,20 @@ enum hvm_intblk nhvm_interrupt_blocked(struct vcpu *v)
      return hvm_funcs.nhvm_intr_blocked(v);
  }
+int hvm_set_mode(struct vcpu *v, int mode)
+{
+    if ( mode == 4 )
+    {
+        v->arch.hvm_vcpu.guest_efer &= ~(EFER_LMA | EFER_LME);
+        hvm_update_guest_efer(v);
+    }
+
+    if ( hvm_funcs.set_mode )
+        return hvm_funcs.set_mode(v, mode);
+
+    return 0;
+}
-EOPNOTSUPP?

Why do you think this should be an error? I probably will need to update this to handle mode==8 for calls from switch_native() as you pointed out above but in general it seems to me it should be OK if this procedure doesn't do anything. Below too.

-boris


--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1763,6 +1763,22 @@ static void vmx_enable_msr_exit_interception(struct 
domain *d)
                                           MSR_TYPE_W);
  }
+int vmx_set_mode(struct vcpu *v, int mode)
+{
+
+    if ( !is_pvh_vcpu(v) )
+        return 0;
+
+    if ( mode == 4 )
+    {
+        vmx_vmcs_enter(v);
+        __vmwrite(GUEST_CS_AR_BYTES, 0xc09b);
+        vmx_vmcs_exit(v);
+    }
+
+    return 0;
+}
Again -EOPNOTSUPP?

Jan



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