Subject: Re: efi_enabled(EFI_PARAVIRT) use

From: Matt Fleming <[email-masked]>
Date: Sat, 30 Apr 2016 21:44:20 +0100

On Sat, 30 Apr, at 10:14:42PM, Shannon Zhao wrote:
> Sure. How should I add this change? Rework this patch or add new one on
> top of it?
 
Rework this patch, please.

> Yes, in this patch we could set EFI_RUNTIME_SERVICES flag in
> fdt_find_hyper_node instead of setting EFI_PARAVIRT flag, and then bail
> out early in arm_enable_runtime_services() as you said. Then call
> xen_efi_runtime_setup() in xen_guest_init().
 
Sounds good.

> While I still have a question, in this patch we use
> efi_enabled(EFI_PARAVIRT) as a condition to make fdt_find_uefi_params()
> and efi_get_fdt_params() execute different ways. So it needs to find a
> new condition for that if we need to get rid of EFI_PARAVIRT. One I
> think is that xen_initial_domain() check. Is that fine?

Hmm... why do you actually need to check whether you're running on a
PV machine in fdt_find_uefi_params()? Can't you infer that from the DT
params you discover?

I could understand maybe only accepting the "xen,uefi-system-table"
property if IS_ENABLED(CONFIG_XEN) but surely you don't also need to
filter based on whether you're booting a PV kernel?

Let me put it this way: when would you see "xen,uefi-system-table" and
*not* be booting a PV kernel?