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Re: [Xen-devel] [PATCH Remus v1 5/8] tools/libxc: defer the setting of HVM_PARAM_IDENT_PT

Hi Andrew,

On 05/07/2015 11:24 PM, Andrew Cooper wrote:
On 07/05/15 14:59, Hongyang Yang wrote:

On 05/07/2015 06:35 PM, Andrew Cooper wrote:
On 07/05/15 07:37, Yang Hongyang wrote:
Set the hvm param HVM_PARAM_IDENT_PT second time will fail.
So defer the setting of HVM_PARAM_IDENT_PT.

Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>

I would argue that this is a Xen bug, not a migration bug.  There is
nothing conceptually wrong with setting this param multiple times.

I noticed that in legacy migration, this was set multiple times, so
this patch is only a workaround that will avoid the fail in my test.
will try your hypervisor patch tomorrow.

Try this version, which has been rebased over Pauls' cleanup in this
area which has just been committed to staging.

A quick test show that this patch fix the problem, will you send this
patch separately or I put this patch into my series?


diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 371fd33..941e9ea 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5710,12 +5710,13 @@ static int hvmop_set_param(
              rc = -EINVAL;
      case HVM_PARAM_IDENT_PT:
-        rc = -EINVAL;
-        if ( d->arch.hvm_domain.params[a.index] != 0 )
-            break;
          rc = 0;
-        if ( !paging_mode_hap(d) )
+        d->arch.hvm_domain.params[a.index] = a.value;
+        /*
+         * Only actually required for VT-x lacking unrestricted_guest
+         * capabilities.  Short circuit the pause if possible.
+         */
+        if ( !paging_mode_hap(d) || !cpu_has_vmx )

@@ -5729,7 +5730,6 @@ static int hvmop_set_param(

          rc = 0;
-        d->arch.hvm_domain.params[a.index] = a.value;
          for_each_vcpu ( d, v )



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