Subject: Re: efi_enabled(EFI_PARAVIRT) use
To: Matt Fleming <matt@codeblueprint.co.uk>
References: <20160429142020.4499e185@canb.auug.org.au>
 <20160429063936.GA28320@gmail.com>
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 <20160429143931.GG2839@codeblueprint.co.uk>
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 <5724BDD2.5020600@linaro.org> <20160430204420.GM2839@codeblueprint.co.uk>
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>
From: Shannon Zhao <shannon.zhao@linaro.org>
Message-ID: <572576E2.7060508@linaro.org>
Date: Sun, 1 May 2016 11:24:18 +0800
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On 2016年05月01日 04:44, Matt Fleming wrote:
>> 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()?
Because the UEFI params for Dom0 are located under /hypervisor/uefi node
instead of /chosen. So it needs to check whether it's a Dom0 then search
and parse different node with different params arrays.

> 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?
So it still needs add another check to firstly parse the fdt to see if
there is "xen,uefi-system-table" under /hypervisor/uefi node, right? I
think it's a bit redundant compared with xen_initial_domain().

Thanks,
-- 
Shannon