[patch 2/4] remove extra acpi_rsdp command line for efi

[Simon Horman]

On Tue, Oct 29, 2013 at 10:36:36AM +0800, Dave Young wrote:
> On 10/29/13 at 11:04am, Simon Horman wrote:
> > On Mon, Oct 28, 2013 at 12:10:40PM -0400, Vivek Goyal wrote:
> > > On Mon, Oct 28, 2013 at 10:51:19AM +0000, Matthew Garrett wrote:
> > > > On Mon, Oct 28, 2013 at 06:45:32PM +0800, Dave Young wrote:
> > > > > On 10/28/13 at 10:39am, Matthew Garrett wrote:
> > > > > > On Mon, Oct 28, 2013 at 06:34:12PM +0800, Dave Young wrote:
> > > > > > > On 10/28/13 at 10:12am, Matthew Garrett wrote:
> > > > > > > > Right, but previously acpi_rsdp was passed automatically and now it 
> > > > > > > > won't be?
> > > > > > > 
> > > > > > > Yes, it was. I'm removing them in kexec-tools patches for efi runtime support.
> > > > > > 
> > > > > > If I upgrade kexec-tools and try to launch an old kernel, I now need to 
> > > > > > add an extra parameter?
> > > > > 
> > > > > Yes, it should work by passing the acpi_rsdp= via --append
> > > > 
> > > > Yes, that's my point. You're breaking old configurations by requiring 
> > > > the user to pass an additional argument.
> > > 
> > > Yes this is a problem. Of course solution is easy by always passing
> > > acpi_rsdp on command line. But in long term this is a problem. In the
> > > sense, I am not sure how to cleanup the kexec-tools code as things improve.
> > > Now we will support the EFI properly and still pass acpi_rsdp always in
> > > an effort to matain backward compatibility.
> > > 
> > > For a very long time kexec-tools were not automatically appending
> > > acpi_rsdp and user were supposed to add it on command line. We were
> > > carrying this change in kdump scripts and pushed this change into
> > > kexec-tools. In hindsight, it looks like that hardcoding parameters
> > > in kexec-tools is a bad idea. It is hard to get rid of them in future.
> > 
> > I tend to agree.  However, if the parameters end up being hard coded
> > elsewhere, for example in widely used wrapper scripts, then I think that
> > the same problem still exists. Just outside of kexec-tools itself.
> 
> Kernel has a rule of not breaking userspace, does kexec-tools also have
> the policy? Maybe user or distribution carry that will be slight better
> so upstream kexec code will be cleaner..

I'm not sure that we have had to make a policy decision with regards
to this. At least not recently. But yes, I think it should be a goal
of kexec-tools not to break its users.