Thanks for such an interesting question. I checked with an engineer who programs our Intel iSCSI Remote Boot option to find out if this was possible. The short answer is no.
Intel iSCSI Remote Boot only works under legacy BIOS with native PCI device support. The guest OS will perform an emulation of this part of the boot process where no native PCI device options will be loaded into memory. Therefore, the Intel iSCSI Remote Boot option is not available to the virtual machine.
I have heard that there might be remote boot for some guest operating systems through a PXE emulation, but that would be through software meant to work with the virtualization software rather than through the option ROM on the network adapter. I do not know if that is something you could do with Xen or not.
Thanks for the info.
I have a query on VF's config space of Intel gigabit ET dual port server adapter.
As we know, iscsi remote works with firmware present in option ROM pointed by Expansion ROM BAR in PF's config space. When i check VF's config space, there is no such Expansion ROM BAR. Is there any way for VMM to emulate this Expansion ROM BAR in VF's config space.
According to one of our virtualization experts, "The VF (Virtual Function) essentially provides direct hardware access for transmit and receive, it does not expose any pre-boot capabilities such as PXE or iSCSI Boot. This type of functionality would have to be provided by the hypervisor itself."
The Xen* community might be a place where you could pursue support for this type of function in the hypervisor.