Re: Drop CSM support in OvmfPkg?

[Andrew Fish <afish@apple.com>]

> On Jan 22, 2019, at 7:43 PM, Ni, Ray <ray.ni@intel.com> wrote:
> 
>> -----Original Message-----
>> From: David Woodhouse <dwmw2@infradead.org <mailto:dwmw2@infradead.org>>
>> Sent: Wednesday, January 23, 2019 12:23 AM
>> To: Ni, Ray <ray.ni@intel.com <mailto:ray.ni@intel.com>>; Gerd Hoffmann <kraxel@redhat.com <mailto:kraxel@redhat.com>>;
>> Laszlo Ersek <lersek@redhat.com <mailto:lersek@redhat.com>>; Richardson, Brian
>> <brian.richardson@intel.com <mailto:brian.richardson@intel.com>>
>> Cc: Justen, Jordan L <jordan.l.justen@intel.com <mailto:jordan.l.justen@intel.com>>; edk2-devel@lists.01.org <mailto:edk2-devel@lists.01.org>;
>> Kevin O'Connor <kevin@koconnor.net <mailto:kevin@koconnor.net>>; Anthony Perard
>> <anthony.perard@citrix.com <mailto:anthony.perard@citrix.com>>
>> Subject: Re: Drop CSM support in OvmfPkg?
>> 
>> On Tue, 2019-01-22 at 16:13 +0000, Ni, Ray wrote:
>>> David,
>>> I'd like to re-start the discussion.
>>> Could you please kindly explain the background/reason of adding CSM
>>> support in OVMF?
>>> Maybe knowing the reason can help to make further decisions of
>>> whether to
>>> A. keep it outside OvmfPkg
>>> B. keep it inside OvmfPkg
>>> C. maybe have a chance to just remove the CSM support after
>>> revisiting
>> 
>> 
>> The idea was to make it simple to have a single firmware image for
>> virtual machines which would support both UEFI and Legacy boot for
>> guests simultaneously.
>> 
>> In libvirt there has been an alternative approach, where the BIOS image
>> is switched between OVMF and SeaBIOS according to the configuration of
>> the guest VM.
>> 
>> That's fine for libvirt, but in situations where VM hosting is provided
>> as a service, it becomes quite painful to manage the 'UEFI' vs.
>> 'Legacy' flags on guest images and then switch firmware images
>> accordingly. A one-size-fits-all BIOS using OVMF+CSM is very much
>> preferable.
> 
> David,
> Thanks for sharing. I now understand that you do have a need of
> CSM + UEFI OVMF image.
> A very straightforward idea is to move all COM components you needed
> into OvmfPkg. But Laszlo as the OvmfPkg owner may disagree with this.
> So maybe you could set up another (github) repo and clone all the CSM components
> there.
> EDKII build tool supports to build firmware from multiple repos.
> That's how we can have edk2-platforms and to-be-created edk2-app.
> In practical, you could create a new csm repo.
> Laszlo/Gerd who don't care about CSM can just build OVMF image from edk2 repo.
> You can build the OVMF image from edk2 and csm repo.
> 

Ray,

I kind or agree at this point CSM is really more interesting for virtual machines vs. real platforms. I guess the interesting question to ask is do we want to start making it more part of the virtual machines that happen to be checked into TianoCore, or should we keep it more generic? The thinking being the CSM is likely upstreamed in other more commercial VMs? Can we just add a readme to the current CSM package and explain it mostly exists to support VMs? 

Thanks,

Andrew Fish

> We can have a call if you are ok. I can explain how that can work in details.
> 
> Thanks,
> Ray 
> 
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