linux-kernel - Re: [PATCH] Xen: EFI: Parse DT parameters for Xen specific UEFI

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Message-ID: <5733E8CF.3070004@huawei.com>
Date:	Thu, 12 May 2016 10:22:07 +0800
From:	Shannon Zhao <zhaoshenglong@...wei.com>
To:	Matt Fleming <matt@...eblueprint.co.uk>,
	Shannon Zhao <shannon.zhao@...aro.org>
CC:	<linux-arm-kernel@...ts.infradead.org>, <catalin.marinas@....com>,
	<will.deacon@....com>, <sstabellini@...nel.org>,
	<stefano@...reto.com>, <julien.grall@....com>,
	<ard.biesheuvel@...aro.org>, <xen-devel@...ts.xen.org>,
	<devicetree@...r.kernel.org>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <peter.huangpeng@...wei.com>
Subject: Re: [PATCH] Xen: EFI: Parse DT parameters for Xen specific UEFI



On 2016/5/12 7:24, Matt Fleming wrote:
> On Wed, 11 May, at 09:35:47PM, Shannon Zhao wrote:
>>> > > 
>>> > > Also, why do you need to setup efi.runtime_version here? Isn't that
>>> > > done inside uefi_init()?
>>> > > 
>> > I don't see any codes which setup efi.runtime_version in uefi_init().
>  
> Look in the EFI tree,
> 
>   https://git.kernel.org/cgit/linux/kernel/git/mfleming/efi.git/tree/drivers/firmware/efi/arm-init.c?h=next#n120
> 
Ah, there are some patches in EFI tree introducing this change, but they
are not in kernel matser but I didn't notice this, sorry.

>>> > > Here is how I would have expected this patch to look:
>>> > > 
>>> > >   - Add FDT code to find hypervisor EFI params
>>> > > 
>>> > >   - Force enable EFI_RUNTIME_SERVICES for Xen and call
>>> > >     xen_efi_runtime_setup() inside xen_guest_init()
>>> > > 
>>> > >   - Change arm_enable_runtime_services() to handle the case where
>>> > >     EFI_RUNTIME_SERVICES is already set
>>> > > 
>>> > > Am I misunderstanding some ordering issues?
>> > 
>> > Since xen_guest_init() and arm_enable_runtime_services() are both
>> > early_initcall and the calling order is random I think.
> Urgh, right, I missed that.
> 
>> > And when we call xen_efi_runtime_setup() and setup
>> > efi.runtime_version in xen_guest_init(), the efi.systab might be
>> > NULL. So it needs to map the systanle explicitly before we use
>> > efi.systab.
> Could you explain why you need to copy efi.runtime_version instead of
> letting the existing code in uefi_init() set it up?
> 
> Also, efi.systab isn't used by xen_efi_runtime_setup() as far I can
> see, not sure why you need that either?
As said above, I will rebase this patch on top of the EFI next branch.

Thanks,
-- 
Shannon