From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 1/1] xen-hvm.c: Add support for Xen access
	to vmport
Date: Mon, 29 Sep 2014 14:21:35 +0200
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To: Alexander Graf <agraf@suse.de>, Don Slutz <dslutz@verizon.com>, qemu-devel@nongnu.org
Cc: xen-devel@lists.xensource.com, Marcel Apfelbaum <marcel.a@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Markus Armbruster <armbru@redhat.com>, Anthony Liguori <aliguori@amazon.com>, =?windows-1252?Q?Andreas_F=E4rber?= <afaerber@suse.de>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Il 29/09/2014 13:53, Alexander Graf ha scritto:
> 
>   cpu_handle_ioreq()
>   {
>     ...
> 
>     if (req->type == IOPORT_REGISTERS_SYNCHRONIZED) {
>         cpu->xen_vcpu_dirty = true;
>         synchronize_xen_to_env(xenptr, cpu);
>     }
> 
>     handle_ioreq();
> 
>     if (req->type == IOPORT_REGISTERS_SYNCHRONIZED) {
>         cpu->xen_vcpu_dirty = false;
>         synchronize_env_to_xen(xenptr, cpu);
>     }
> 
>     ...
>   }
> 
>   void xen_cpu_synchronize_state(CPUState *cpu)
>   {
>     assert(cpu->xen_vcpu_dirty);
>   }
> 
> Then no changes to the vmport code would be necessary and this problems
> where some code path wants to do direct access to registers
> automatically tells us that things are broken.

Yeah, that would be possible.  You do not even need synchronize_state,
it seems to me that it introduces more complication for little gain.

Paolo