Date: Sat, 30 Apr 2016 21:44:20 +0100
From: Matt Fleming <matt@codeblueprint.co.uk>
To: Shannon Zhao <shannon.zhao@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Jeremy Fitzhardinge <jeremy@goop.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
        Xen Devel <Xen-devel@lists.xensource.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>, linux-next@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: efi_enabled(EFI_PARAVIRT) use
Message-ID: <20160430204420.GM2839@codeblueprint.co.uk>
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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?