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Date: Fri, 2 Mar 2018 11:50:09 +0000
From: Anthony PERARD <anthony.perard@citrix.com>
Message-ID: <20180302115009.GF1799@perard.uk.xensource.com>
References: <20171207101812.23602-1-haozhong.zhang@intel.com>
	<20171207101812.23602-4-haozhong.zhang@intel.com>
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Subject: Re: [Qemu-devel] [RFC QEMU PATCH v4 03/10] hostmem-xen: add a host
 memory backend for Xen
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To: qemu-devel@nongnu.org, xen-devel@lists.xenproject.org, Stefano Stabellini <sstabellini@kernel.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Dan Williams <dan.j.williams@intel.com>, Chao Peng <chao.p.peng@linux.intel.com>, Eduardo Habkost <ehabkost@redhat.com>, Igor Mammedov <imammedo@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>

On Wed, Feb 28, 2018 at 03:56:54PM +0800, Haozhong Zhang wrote:
> On 02/27/18 16:41 +0000, Anthony PERARD wrote:
> > On Thu, Dec 07, 2017 at 06:18:05PM +0800, Haozhong Zhang wrote:
> > > @@ -108,7 +109,10 @@ void pc_dimm_memory_plug(DeviceState *dev, MemoryHotplugState *hpms,
> > >      }
> > >  
> > >      memory_region_add_subregion(&hpms->mr, addr - hpms->base, mr);
> > > -    vmstate_register_ram(vmstate_mr, dev);
> > > +    /* memory-backend-xen is not backed by RAM. */
> > > +    if (!xen_enabled()) {
> > 
> > Is it possible to have the same condition as the one used in
> > host_memory_backend_memory_complete? i.e. base on whether the memory
> > region is mapped or not (backend->mr.ram_block).
> 
> Like "if (!xen_enabled() || backend->mr.ram_block))"? No, it will mute
> the abortion (vmstate_register_ram --> qemu_ram_set_idstr ) caused by
> the case that !backend->mr.ram_block in the non-xen environment.

In non-xen environment, vmstate_register_ram() will be called, because
!xen_enabled() is true, it would not matter if there is a ram_block or
not.

But if there is a memory-backend that can run in a xen environment that
have a ram_block, vmstate_register_ram would not be called in the
origial patch, but if we use (!xen_enabled() || vmstate_mr->ram_block)
as condition then vmstate_register_ram will be called.

Is this make sense?

> > > +        vmstate_register_ram(vmstate_mr, dev);
> > > +    }
> > >      numa_set_mem_node_id(addr, memory_region_size(mr), dimm->node);
> > >  
> > >  out:

-- 
Anthony PERARD