Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down

From	Dave Young <dyoung@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down
Date	2017-04-07 09:50 +0200
Message-ID	<ttwOC-4ar-21@gated-at.bofh.it> (permalink)
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On 04/07/17 at 08:05am, David Howells wrote:
> Dave Young <dyoung@redhat.com> wrote:
> 
> > > > This option allows userspace to pass the RSDP address to the kernel, which
> > > > makes it possible for a user to circumvent any restrictions imposed on
> > > > loading modules.  Ignore the option when the kernel is locked down.
> > > 
> > > I'm not really sure here.
> > > 
> > > What exactly is the mechanism?
> > 
> > Actually this acpi_rsdp param is created for EFI kexec reboot in old
> > days when we had not supported persistent efi vm space across kexec
> > reboot. At that time kexec reboot runs as noefi mode, it can not find
> > the acpi root table thus kernel will hang early.
> > 
> > Now kexec can support EFI boot so this param is not necessary for most
> > user unless they still use efi=old_map.
> 
> Is this patch now unnecessary?

I think it is still necessary because the acpi_rsdp kernel param is still
a valid paramater and one can still pass a pointer to be recognized as acpi
root pointer.

Maybe "imposed on loading modules" is not clear which can be dropped.

Thanks
Dave

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[PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the kernel  has been locked down David Howells <dhowells@redhat.com> - 2017-04-05 22:20 +0200
  Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the kernel  has been locked down "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-06 21:50 +0200
    Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the  kernel has been locked down Dave Young <dyoung@redhat.com> - 2017-04-07 08:40 +0200
      Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down David Howells <dhowells@redhat.com> - 2017-04-07 09:10 +0200
        Re: [PATCH 17/24] acpi: Ignore acpi_rsdp kernel param when the  kernel has been locked down Dave Young <dyoung@redhat.com> - 2017-04-07 09:50 +0200

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