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xen-devel
Re: [Xen-devel] [PATCH 2 of 3] Enable UEFI BIOS(OVMF) support in Xen-uns
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To: |
Andrei Warkentin <andreiw@xxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [PATCH 2 of 3] Enable UEFI BIOS(OVMF) support in Xen-unstable HVM |
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From: |
Jordan Justen <jljusten@xxxxxxxxx> |
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Date: |
Tue, 9 Aug 2011 16:01:52 -0700 |
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Cc: |
Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, "edk2-devel@xxxxxxxxxxxxxxxxxxxxx" <edk2-devel@xxxxxxxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, Keir Fraser <keir.xen@xxxxxxxxx>, Bei Guan <gbtju85@xxxxxxxxx> |
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Tue, 09 Aug 2011 16:06:50 -0700 |
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<CAEQjb-SRJ7243mf0cEHZPUpt_hfXcBdZgs1AGL_Ep144HpRkrg@xxxxxxxxxxxxxx> <CA4F6783.1E6DB%keir.xen@xxxxxxxxx> <20026.48387.889557.9445@xxxxxxxxxxxxxxxxxxxxxxxx> <CAEQjb-TLJTct7NOcJgg0iam5-9XqMc8DHsihXKx8CbKHU5QaxQ@xxxxxxxxxxxxxx> <1312885472.26263.82.camel@xxxxxxxxxxxxxxxxxxxxxx> <CAEQjb-Tk+R3nZ54H_kz2Jb+2sc79L07bZ4gNALAiEDtiW8t8Og@xxxxxxxxxxxxxx> <1312900756.26263.144.camel@xxxxxxxxxxxxxxxxxxxxxx> <CALfQTu5HHJqztgMQHsuh3QtJbDGQz+N7-3SbPmhnK+hEcrT7FA@xxxxxxxxxxxxxx> |
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On Tue, Aug 9, 2011 at 15:35, Andrei Warkentin <andreiw@xxxxxxxxxxxx> wrote:
> On Tue, Aug 9, 2011 at 9:39 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
> wrote:
>> No. Hardware devices have a special BAR which can be used to map their
>> option ROM. BIOSes (i.e. real ones on physical machines) use this in
>> order to map the option ROMs and copy or run them etc. SeaBIOS also
>> supports this and qemu supports emulating these BARs for the given
>> devices by providing the contents of a specific file on the host file
>> system and so we don't load any VGA BIOS in hvmloader in that case and
>> just let seabios and qemu take care of it via this mechanism.
>>
>> So what I'm suggesting is that OVMF should (and possibly already does)
>> support this operation and should load the VGA rom itself from the VGA
>> devices ROM BAR. If the VGABIOS for OVMF needs to be different to what
>> would be normally need with a legacy BIOS then we can enhance QEMU to
>> provide the option to request alternative ROM images be used.
>>
>> This model makes sense since a device's option-ROM is tied more to the
>> specific device than it is to the BIOS etc.
>
> I think long-term this is doable and a good idea. Obviously EFI does
> support loading drivers from PCI ROM, yet right now OVMF just builds
> in the relevant video drivers into the firmware.
> Because drivers bind only to specific hardware, it is safe to contain
> all possible video drivers. I think for now we can just claim no "vga
> rom" as far hvmloader is concerned.
Actually, we don't include the video drivers in the main firmware
image. For qemu, vgabios.bin is loaded into RAM at 0xc0000, and we
find it there.
I think qemu may be moving towards loading vgabios.bin into the PCI
ROM-BAR, or maybe they already do.
Anyway, it would be best to load the video rom from the PCI device if
Xen supports it already.
-Jordan
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