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Peter Anvin" , Jiri Olsa , Ard Biesheuvel , ACPI Devel Maling List , the arch/x86 maintainers , Pierre-Louis Bossart , Alexander Shishkin , Ingo Molnar , Darren Hart , Len Brown , Arnd Bergmann , linux-pm , Arnaldo Carvalho de Melo , Hans de Goede , Mark Brown , Borislav Petkov , Steven Rostedt , Namhyung Kim , Thomas Gleixner , platform-driver-x86@vger.kernel.org, "VMware, Inc." , Tony Luck , Greg Kroah-Hartman , "Rafael J. Wysocki" , Takashi Iwai , Sean Christopherson , Linux Kernel Mailing List , Andy Shevchenko Subject: Re: [alsa-devel] [PATCH 00/12] treewide: break dependencies on x86's RM header X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Tue, 19 Nov 2019 at 12:10, Ingo Molnar wrote: > > > * Sean Christopherson wrote: > > > x86's asm/realmode.h, which defines low level structures, variables and > > helpers used to bring up APs during SMP boot, ends up getting included in > > practically every nook and cranny of the kernel because the address used > > by ACPI for resuming from S3 also happens to be stored in the real mode > > header, and ACPI bleeds the dependency into its widely included headers. > > > > As a result, modifying realmode.h for even the most trivial change to the > > boot code triggers a full kernel rebuild, which is frustrating to say the > > least as it some of the most difficult code to get exactly right *and* is > > also some of the most functionally isolated code in the kernel. > > > > To break the kernel's widespread dependency on realmode.h, add a wrapper > > in the aforementioned ACPI S3 code to access the real mode header instead > > of derefencing the header directly in asm/acpi.h and thereby exposing it > > to the world via linux/acpi.h. > > > > Build tested on x86 with allyesconfig and allmodconfig, so hopefully there > > aren't more build issues lurking, but at this point it wouldn't surprise > > me in the least if this somehow manages to break the build. > > > > Based on tip/master, commit ceceaf1f12ba ("Merge branch 'WIP.x86/cleanups'"). > > > > Patch Synopsis: > > - Patches 01-09 fix a variety of build errors that arise when patch 12 > > drops realmode.h from asm/acpi.h. Most of the errors are quite absurb > > as they have no relation whatsoever to x86's RM boot code, but occur > > because realmode.h happens to include asm/io.h. > > Yeah, these kind of parasitic header dependencies are the main driving > force behind kernel header spaghetti hell: it's super easy to add a new > header, but very hard to remove them... > > Hence they practically only accumulate. > > As a result header removal patches get priority, from me at least. :-) > > > - Patch 10 removes a spurious include of realmode.h from an ACPI header. > > > > - Patches 11 and 12 implement the wrapper and move it out of acpi.h. > > So if the ACPI maintainers are fine with -tip carrying patches #11 and #12 > then I'd be glad to route these patches upstream. > > I've applied them to tip:WIP.core/headers as a work-in-progress tree, and > I'm testing them on randconfigs to make sure there's no broken > dependencies. I'll wait for the ACPI acks. > > I edited the title of patch 12 slightly, to: > > c8bceb321209: x86/ACPI/sleep: Move acpi_wakeup_address() definition into sleep.c, remove from > > to make sure the big header dependency change is obvious at first sight. > I'm fine with the patches but can we drop the fixes headers please? This doesn't actually fix anything, and touching early boot stuff for no good reason should be avoided imo. _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org https://mailman.alsa-project.org/mailman/listinfo/alsa-devel