linux-kernel - Re: [PATCH v7 12/17] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56FE3E85.60403@huawei.com>
Date:	Fri, 1 Apr 2016 17:25:25 +0800
From:	Shannon Zhao <zhaoshenglong@...wei.com>
To:	Mark Rutland <mark.rutland@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huangpeng (Peter)" <peter.huangpeng@...wei.com>,
	<julien.grall@....com>,
	"Stefano Stabellini" <stefano.stabellini@...rix.com>,
	Shannon Zhao <shannon.zhao@...aro.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH v7 12/17] ARM64: ACPI: Check if it runs on Xen to enable
 or disable ACPI



On 2016/3/31 20:42, Mark Rutland wrote:
> On Thu, Mar 31, 2016 at 01:44:08PM +0200, Ard Biesheuvel wrote:
>> > The heuristic is there to decide whether some DTB image contains a
>> > complete description of the platform, or only some data handed over by
>> > the bootloader. Arguably, a DT containing both /chosen and /hypervisor
>> > but nothing else can still not describe an actual platform, and
>> > whether we execute under Xen or not is completely irrelevant.
> I disagree somewhat.
> 
> In general, a /hypervisor node may not be a Xen node, and could
> potentially imply some platform description. As /hypervisor is a generic
> name up for grabs by any hypervisor, we simply cannot make assumptions
> about it.
> 
> As /chosen is a special reserved path that implies a particular binding
> and has no compatible string, so checking its path alone is correct.
> 
> While we do check that the /hypervisor node is "xen,xen" compatible
> elsewhere, the canonical mechanism of checking for a Xen node (as
> opposed to any hypervisor's node) is to check the compatible string.
> 
> If we are going to handle nodes for other hypervisors while treating the
> DTB as empty, we need code and discussion regarding said hypervisor.
> 
> Hence, for checking for a Xen /hypervisor node, I would prefer we
> checked the compatible string rather than the path.
> 
> An is_xen_node() helper (which could also check that the path is
> "/hypervisor") would avoid having redundant, subtly distinct ways of
> checking, and would explicitly document precisely what we are checking
> for.

So if we use is_xen_node(), do we need to call xen_initial_domain()
again? I still think here is_xen_node() and xen_initial_domain() have
same meaning. Why do we need that?

If it really needs is_xen_node(), I will not factor
fdt_find_hyper_node() in patch 11 since it uses flat DT while here it's
going to use unflatten DT.

Thanks,
-- 
Shannon