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Date: Sat, 22 Dec 2018 01:37:58 +0800
From: Yu Zhang <yu.c.zhang@linux.intel.com>
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Subject: Re: [Qemu-devel] [PATCH v3 1/2] intel-iommu: differentiate host
 address width from IOVA address width.
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>, Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org, Peter Xu <peterx@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On Fri, Dec 21, 2018 at 12:04:49PM -0500, Michael S. Tsirkin wrote:
> On Sat, Dec 22, 2018 at 12:09:44AM +0800, Yu Zhang wrote:
> > Well, my understanding of the vt-d spec is that the address limitation in
> > DMAR are referring to the same concept of CPUID.MAXPHYSADDR. I do not think
> > there's any different in the native scenario. :)
> 
> I think native machines exist on which the two values are different.
> Is that true?

I think the answer is not. My understanding is that HAW(host address wdith) is
the maximum physical address width a CPU can detects(by cpuid.0x80000008).

I agree there are some addresses the CPU does not touch, but they are still in
the physical address space, and there's only one physical address space...

B.R.
Yu