Messages in this thread | | | Date | Wed, 6 Dec 2006 00:08:25 +0900 | From | "Magnus Damm" <> | Subject | Re: [PATCH 00/02] kexec: Move segment code to assembly files |
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On 12/5/06, Vivek Goyal <vgoyal@in.ibm.com> wrote: > On Tue, Dec 05, 2006 at 10:37:57PM +0900, Magnus Damm wrote: > > kexec: Move segment code to assembly files > > > > The following patches rearrange the lowlevel kexec code to perform idt, > > gdt and segment setup code in assembly on the code page instead of doing > > it in inline assembly in the C files. > > > > I don't think we should be doing this. I would rather prefer code to > keep in C for easier debugging, readability and maintenance.
I prefer to write code in C too, but I don't see how wrapping assembly instructions in inline C makes the code any easier compared to raw assembly. Either you understand the assembly or you don't.
> > Our dom0 Xen port of kexec and kdump executes the code page from the > > hypervisor when kexec:ing into a new kernel. Putting as much code as > > possible on the code page allows us to keep the amount of duplicated > > code low. > > > > Is Xen going upstream now? I heard now lhype+KVM seems to be the way. > Even if it is required, we should do it once Xen goes in.
I am not sure about status of the Xen merging effort. domU seemed to be the top priority last time I heard something, but this change only affects dom0 so it is probably even further away.
> You have already moved page table setup code to assembly and we should > be getting rid of that code too.
This was recommended to me by Eric if I'm not mistaken, but if we can move out parts of the assembly code to C then that would be great.
> I would rather live with duplicated code than moving more code in assembly > which can be written in C. Understanding and debugging assembly code > is such a big pain.
Again, I think that is true for C code - not for inline assembly in C files. But I guess you are talking about the already merged page table a patches. My first version implemented the code in C, have a look at the function create_mapping() which I think is very clear:
http://lists.osdl.org/pipermail/fastboot/2006-May/002838.html
The important question IMO is if this should be merged ahead of the rest of the Xen stuff, and maybe it shouldn't.
Thanks,
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