Re: [Xen-devel] PXE boot with e1000 using OVMF

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Sep 20, 2018 at 12:33:42PM +0100, Anthony PERARD wrote:
> On Wed, Sep 19, 2018 at 11:04:22AM -0600, Tamas K Lengyel wrote:
> > On Wed, Sep 19, 2018 at 10:36 AM Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > >
> > > On Wed, Sep 12, 2018 at 11:54:02AM -0600, Tamas K Lengyel wrote:
> > > > HI all,
> > > > I'm experimenting with OVMF and I checked to see if OVMF can do PXE
> > > > boot out-of-the box with a e1000 emulated network interface and was
> > > > surprised to find that it does not. After reading some of the prior
> > > > discussions on the topic (https://lists.gt.net/xen/devel/382432 and
> > > > https://lists.xenproject.org/archives/html/xen-users/2015-09/msg00059.html)
> > > > I was able to get the menu options to show up by copying efi-e1000.rom
> > > > that gets installed by Xen's QEMU build into the disk of the VM and
> > > > then loading with loadpcirom manually in the EFI shell. From the prior
> > > > discussions it sounds to me like this option rom should have been
> > > > automatically served by QEMU to OVMF when the VM started as an
> > > > OptionROM. So is this a bug or what's missing?
> > >
> > > Doesn't QEMU load the option ROM automatically when you specify e1000?
> > >
> > > I _think_ it loads option ROM automatically because I have seen complain
> > > that if you configure too many emulated NICs the guest runs out of
> > > memory.
> > 
> > I compiled QEMU with DEBUG_PCI enabled in hw/pci/pci.c and then the
> > log shows efi-e1000.rom being loaded. However, AFAICT since PCI
> > enumeration is disabled in OVMF when running under Xen (I'm not
> > exactly sure why) the option rom never gets executed as it only gets
> 
> It's because hvmloader (which is runned before OVMF start) takes care of
> enumerating the PCI bus. OVMF only has to read the information:
> via OvmfPkg/Library/PciHostBridgeLib/XenSupport.c

Indeed.

> 
> I can try to find out what's needed in order to load an option rom, or
> ask on edk2-devel.

Thank you!

Wei.

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