> -----Original Message----- > From: 'Greg Kroah-Hartman' [mailto:gre...@linuxfoundation.org] > Sent: Friday, June 15, 2018 4:06 PM > To: Daniel Sangorrin <daniel.sangor...@toshiba.co.jp> > Cc: linux-kernel@vger.kernel.org; sta...@vger.kernel.org; 'Andy Lutomirski' > <l...@kernel.org>; 'Rik van Riel' <r...@redhat.com>; 'Borislav Petkov' > <b...@alien8.de>; 'Brian Gerst' <brge...@gmail.com>; 'Dave Hansen' > <dave.han...@linux.intel.com>; 'Denys Vlasenko' <dvlas...@redhat.com>; > 'Fenghua Yu' <fenghua...@intel.com>; 'H. Peter Anvin' <h...@zytor.com>; 'Josh > Poimboeuf' <jpoim...@redhat.com>; 'Linus Torvalds' > <torva...@linux-foundation.org>; 'Oleg Nesterov' <o...@redhat.com>; 'Peter > Zijlstra' <pet...@infradead.org>; 'Quentin Casasnovas' > <quentin.casasno...@oracle.com>; 'Thomas Gleixner' <t...@linutronix.de>; > pbonz...@redhat.com; 'Ingo Molnar' <mi...@kernel.org> > Subject: Re: [PATCH 4.4 10/24] x86/fpu: Hard-disable lazy FPU mode > > On Fri, Jun 15, 2018 at 02:23:08PM +0900, Daniel Sangorrin wrote: > > > -----Original Message----- > > > From: stable-ow...@vger.kernel.org [mailto:stable-ow...@vger.kernel.org] > On > > > Behalf Of 'Greg Kroah-Hartman' > > > Sent: Friday, June 15, 2018 1:56 PM > > > To: Daniel Sangorrin <daniel.sangor...@toshiba.co.jp> > > > Cc: linux-kernel@vger.kernel.org; sta...@vger.kernel.org; 'Andy > > > Lutomirski' > > > <l...@kernel.org>; 'Rik van Riel' <r...@redhat.com>; 'Borislav Petkov' > > > <b...@alien8.de>; 'Brian Gerst' <brge...@gmail.com>; 'Dave Hansen' > > > <dave.han...@linux.intel.com>; 'Denys Vlasenko' <dvlas...@redhat.com>; > > > 'Fenghua Yu' <fenghua...@intel.com>; 'H. Peter Anvin' <h...@zytor.com>; > 'Josh > > > Poimboeuf' <jpoim...@redhat.com>; 'Linus Torvalds' > > > <torva...@linux-foundation.org>; 'Oleg Nesterov' <o...@redhat.com>; 'Peter > > > Zijlstra' <pet...@infradead.org>; 'Quentin Casasnovas' > > > <quentin.casasno...@oracle.com>; 'Thomas Gleixner' <t...@linutronix.de>; > > > pbonz...@redhat.com; 'Ingo Molnar' <mi...@kernel.org> > > > Subject: Re: [PATCH 4.4 10/24] x86/fpu: Hard-disable lazy FPU mode > > > > > > On Fri, Jun 15, 2018 at 01:24:27PM +0900, Daniel Sangorrin wrote: > > > > Hi Greg, > > > > > > > > > /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 > > > > > */ > > > > > --- a/arch/x86/include/asm/fpu/internal.h > > > > > +++ b/arch/x86/include/asm/fpu/internal.h > > > > > @@ -58,7 +58,7 @@ extern u64 fpu__get_supported_xfeatures_ > > > > > */ > > > > > static __always_inline __pure bool use_eager_fpu(void) > > > > > { > > > > > - return static_cpu_has_safe(X86_FEATURE_EAGER_FPU); > > > > > + return true; > > > > > } > > > > > > > > Since this function returns always true then we can remove the code > depending on > > > lazy FPU mode. > > > > Actually this has already been done in "x86/fpu: Remove use_eager_fpu()" > > > > Ref: https://patchwork.kernel.org/patch/9365883/ > > > > > > > > > static void __init fpu__init_parse_early_param(void) > > > > > { > > > > > - if (cmdline_find_option_bool(boot_command_line, > "eagerfpu=off")) { > > > > > - eagerfpu = DISABLE; > > > > > - fpu__clear_eager_fpu_features(); > > > > > - } > > > > > > > > Since this patch removes the kernel boot parameter "eagerfpu", maybe we > should > > > remove it from the Documentation. > > > > This has also been done by commit "x86/fpu: Finish excising 'eagerfpu'" > > > > Ref: https://patchwork.kernel.org/patch/9380673/ > > > > > > > > I will try backporting those patches unless anyone has any objections. > > > > > > What are the git commit ids of those patches in Linus's tree? No need > > > to point to patchwork links, I don't use that tool. > > > > OK, I got it. > > > > "x86/fpu: Remove use_eager_fpu()": > c592b57347069abfc0dcad3b3a302cf882602597 > > "x86/fpu: Finish excising 'eagerfpu'": > e63650840e8b053aa09ad934877e87e9941ed135 > > Minor nit. For kernel commits, the "normal" way we reference them looks > like this: > c592b5734706 ("x86/fpu: Remove use_eager_fpu()") > e63650840e8b ("x86/fpu: Finish excising 'eagerfpu'") > > Which makes it much easier to read and understand. That's what we use > for the "Fixes:" tag in commits and in other places (text in commit > messages.) > > To automatically generate that format, you can just do: > git show -s --abbrev-commit --abbrev=12 --pretty=format:"%h > (\"%s\")%n" > > I recommend just setting up an alias for the above line, otherwise it's > a pain to have to remember how to do it all the time. Here's what I do: > $ alias gsr='git show -s --abbrev-commit --abbrev=12 --pretty=format:"%h > (\"%s\")%n"' > $ gsr c592b57347069abfc0dcad3b3a302cf882602597 > c592b5734706 ("x86/fpu: Remove use_eager_fpu()") >
Thanks a lot for the detailed explanation. > > Unfortunately, they don't apply cleanly to stable kernels. > > Should be very simple to backport if you want to. Also I need copies > for the 4.9.y tree as well if you do so. OK, I will do it after the OSS Japan next week if you don't mind. I also want to run some tests for the FPU and try different boot parameter combinations (e.g. no387, nofxsr etc) to check I didn't break anything. Thanks, Daniel > > thanks, > > greg k-h
