On Mon, Mar 15, 2021 at 03:58:07PM -0700, Nick Desaulniers wrote:
On Mon, Mar 15, 2021 at 10:53 AM Ard Biesheuvel ardb@kernel.org wrote:
You haven't explained why all this effort is justified to begin with.
Who cares about being able to build 4.19 or 5.4 mainline with Clang 12 and IAS?
Ah, sorry, ChromeOS and Android very much do so. (Google's production kernels as well, though I don't think they have any 32b ARM machines). Android is already building 4.19+ with LLVM_IAS=1 for ARCH=arm64,x86_64,i686. ChromeOS is doing so for 5.4+ for ARCH=arm64,x86_64 as well. I'm not sure precisely what's going on in prodkernel land, but I know they have LLVM_IAS=1 enabled for x86_64. So when Greg says this is "for no real users" I disagree. Maybe no one is using LLVM_IAS=1 for ARCH=arm at this moment, but that was the point of the backports, to enable more distros to do so.
You can't both stay on a "stable" kernel because it's "stable", but then expect a flow of new features. The users which you've mentioned should be migrating to newer kernels instead of attempting to backport features they care about to stable kernels.