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Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

From Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Newsgroups linux.kernel
Subject Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters
Date 2015-09-10 12:30 +0200
Message-ID <q77ha-74B-51@gated-at.bofh.it> (permalink)
References <q75S3-4Wf-9@gated-at.bofh.it> <q76O6-6hn-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Thu, 10 Sep 2015, Mark Rutland wrote:
> Hi,
> 
> I'm not necessarily opposed to the renaming, but I think that this is
> the least important thing to standardize for this to work.
> 
> On Thu, Sep 10, 2015 at 09:41:56AM +0100, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao@linaro.org>
> > 
> > These EFI stub parameters are used to internal communication between EFI
> > stub and Linux kernel and EFI stub creates these parameters. But for Xen
> > on ARM when booting with UEFI, Xen will create a minimal DT providing
> > these parameters for Dom0 and Dom0 is not only Linux kernel, but also
> > other OS (such as FreeBSD) which will be used in the future.
> 
> Currently the Linux EFI stub and kernel have a symbiotic relationship,
> because they're intimately coupled and we don't have kexec (yet) on EFI
> platforms to loosen that coupling.
> 
> If an agent other than the (kernel-specific) stub is going to provide
> this to the kernel, then we need more specified than just the property
> names.
> 
> That at least includes the following:
> 
> * The state of boot services (we currently have the EFI stub call
>   ExitBootServices(), and I believe this is crucial to the plan for
>   kexec).
> 
> * The state of the address map (we currently have the EFI stub call
>   SetVirtualAddressMap()).
> 
> * The virtual address range(s) that SetVirtualAddressMap() may map
>   elements to (this logic is currently in the EFI stub, and this matches
>   the expectations of the kernel that it is tied to).
> 
> > So here we plan to standardize the names by dropping the prefix
> > "linux," and make them common to other OS. Also this will not break
> > the compatibility since these parameters are used to internal
> > communication between EFI stub and kernel.
> 
> For the moment this is true, but will not be once we have kexec, so
> there's a dependency (or anti-dependency) there.
> 
> > Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> > ---
> > Look at [1] for the discussion about this in Xen ML. The purpose of this
> > patch is to standardize the names to make Linux ARM kernel work on Xen
> > with UEFI. Also it hopes other OS(e.g. FreeBSD), which will be used as
> > Dom0 on Xen, could support this mechanism as well.
> > 
> > [1]http://lists.xenproject.org/archives/html/xen-devel/2015-08/msg02250.html
> 
> Per this post, it looks like to pass a DTB to the kernel Xen already
> needs to know it's a Linux kernel...
> 
> I wasn't aware that there was a common standard for arm(64) kernels
> other than a PE/COFF EFI application.
> 
> Does Xen not talk to EFI itself and/or give the kernel a virtual EFI
> interface?

Xen talks to EFI itself but the interface provided to dom0 is somewhat
different: there are no BootServices (Xen calls ExitBootServices before
running the kernel), and the RuntimeServices go via hypercalls (see
drivers/xen/efi.c).
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Thread

[PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Shannon Zhao <zhaoshenglong@huawei.com> - 2015-09-10 11:00 +0200
  Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 12:00 +0200
    Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-10 12:30 +0200
      Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 13:30 +0200
        Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-10 13:50 +0200
          Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 14:20 +0200
            Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of  EFI stub parameters Ian Campbell <ian.campbell@citrix.com> - 2015-09-10 15:00 +0200
              Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names  of EFI stub parameters "Jan Beulich" <JBeulich@suse.com> - 2015-09-10 15:10 +0200
                Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of  EFI stub parameters Ian Campbell <ian.campbell@citrix.com> - 2015-09-10 15:40 +0200
            Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-10 16:00 +0200
              Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Leif Lindholm <leif.lindholm@linaro.org> - 2015-09-10 16:20 +0200
              Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 16:50 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-10 18:20 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 18:30 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Daniel Kiper <daniel.kiper@oracle.com> - 2015-09-11 14:50 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-11 15:20 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-11 15:40 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Daniel Kiper <daniel.kiper@oracle.com> - 2015-09-11 17:50 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Shannon Zhao <zhaoshenglong@huawei.com> - 2015-09-14 11:00 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-14 11:10 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Shannon Zhao <zhaoshenglong@huawei.com> - 2015-09-14 11:40 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-14 11:40 +0200
                Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names  of EFI stub parameters "Jan Beulich" <JBeulich@suse.com> - 2015-09-14 12:40 +0200
                Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of EFI  stub parameters Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2015-09-14 13:20 +0200
                Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names  of EFI stub parameters "Jan Beulich" <JBeulich@suse.com> - 2015-09-14 13:40 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-11 18:40 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-11 18:30 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Daniel Kiper <daniel.kiper@oracle.com> - 2015-09-12 13:50 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-14 11:30 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-14 11:50 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Daniel Kiper <daniel.kiper@oracle.com> - 2015-09-14 14:30 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Ian Campbell <ian.campbell@citrix.com> - 2015-09-11 13:10 +0200
          Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters "Jan Beulich" <JBeulich@suse.com> - 2015-09-10 15:00 +0200
            Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-10 17:00 +0200
              Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters "Jan Beulich" <JBeulich@suse.com> - 2015-09-10 17:10 +0200
                Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Mark Rutland <mark.rutland@arm.com> - 2015-09-11 18:40 +0200
  Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Andrew Turner <andrew@fubar.geek.nz> - 2015-09-10 13:50 +0200
    Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Julien Grall <julien.grall@citrix.com> - 2015-09-10 13:50 +0200
      Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub  parameters Roger Pau Monné <roger.pau@citrix.com> - 2015-09-10 14:10 +0200
        Re: [Xen-devel] [PATCH] efi/libstub/fdt: Standardize the names of  EFI stub parameters Julien Grall <julien.grall@citrix.com> - 2015-09-10 15:00 +0200
  Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Shannon Zhao <zhaoshenglong@huawei.com> - 2015-09-17 14:00 +0200

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