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Re: [Xen-devel] [v5][PATCH 0/5] xen: add Intel IGD passthrough support
- To: "Chen, Tiejun" <tiejun.chen@xxxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>
- From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
- Date: Wed, 25 Jun 2014 11:54:22 +0200
- Cc: peter.maydell@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, stefano.stabellini@xxxxxxxxxxxxx, allen.m.kay@xxxxxxxxx, qemu-devel@xxxxxxxxxx, Kelly.Zytaruk@xxxxxxx, anthony.perard@xxxxxxxxxx, anthony@xxxxxxxxxxxxx, yang.z.zhang@xxxxxxxxx
- Delivery-date: Wed, 25 Jun 2014 09:54:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
Il 25/06/2014 11:50, Chen, Tiejun ha scritto:
For past devices, we know which BARs they use. For future devices, it
would be nice if the PCH/MCH backdoor was specified so that we know they
will leave a free BAR for virtualization.
Now I'm a bit confused about BAR here.
You're saying we will reserve a free BAR to address those information to
expose to guest, but which device does this free BAR belong to? The
video device? Or PCH/MCH?
The video device. If the host device does not have the BAR (which will
be the common case), QEMU can emulate it like this:
- offsets 0x0000..0x0fff map to configuration space of the host MCH
- offsets 0x1000..0x1fff map to configuration space of the host PCH
Of course this is only limited to offsets that are needed by the driver.
Paolo
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