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Re: [Xen-devel] [PATCH] x86: wrap kexec feature with CONFIG_KEXEC



Andrew Cooper <andrew.cooper3@xxxxxxxxxx> writes:

On 01/09/15 11:54, Jan Beulich wrote:
On 01.09.15 at 12:44, <andrew.cooper3@xxxxxxxxxx> wrote:
On 01/09/15 11:36, Ian Campbell wrote:
In general (i.e. not 100% consistently, I think) we have tended to avoid making things user-facing compile time options. Many of the existing CONFIG_* and HAVE_* are really about things which are arch dependent, or require specific porting to each arch etc. I think the KEXEC flag is one of those. This keeps the test matrix more reasonable (unlike e.g. Linux's Kconfig) and also helps us by ensuring that users are mostly running one of a small number of possible configs. I slightly fear that after Kexec you are going to want to strip out more and more stuff...
I for one welcome a Kconfig style approach. We will never be in the same order of magnitude of options as Linux, and it will help to properly modularise the code.
Indeed the idea was brought up a few times already, and I would also welcome such a step (accepting the downside of the larger test matrix). Not the least considering the "no shadow mode" and "big memory" build options that got introduced not so long ago.

From a large attack surface point of view, support for 32bit ABI on 64bit Xen is a welcome candidate for more controlled environments. From a code volume point of view, having things like PV or support configurable would be interesting.

I am not interested in unnecessarily stripping out more and more code. However, I do want to reduce the number of features and backwards-compatibility code-paths that are compiled into my build. Areas like the 32-bit ABI on 64-bit Xen like Andrew mentioned or the legacy Xenlinux ABI are paths that I am interested in pruning. One area I have a preliminary patch for is selectively compiling individual scheduling algorithms in, giving me the option to compile out the experimental algorithms from my build.

Obviously, I can carry my own patchqueues for these types of changes, but
I would prefer to upstream them where possible.

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