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[31.46.246.60]) by smtp.gmail.com with ESMTPSA id v11-20020a05600c470b00b0041488978873sm8462862wmo.44.2024.03.26.12.12.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Mar 2024 12:12:33 -0700 (PDT) Sender: Ingo Molnar Date: Tue, 26 Mar 2024 20:12:31 +0100 From: Ingo Molnar To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Andrew Morton , Dave Hansen , Peter Zijlstra , Borislav Petkov , "H . Peter Anvin" , Linus Torvalds , Thomas Gleixner , Uros Bizjak Subject: Re: [PATCH 1/1] headers/deps: x86/fpu: Make task_struct::thread constant size Message-ID: References: <20240320131908.2708438-1-mingo@kernel.org> <20240320131908.2708438-2-mingo@kernel.org> <20240326174903.GA4539@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240326174903.GA4539@redhat.com> * Oleg Nesterov wrote: > On 03/20, Ingo Molnar wrote: > > > > --- a/arch/x86/kernel/fpu/init.c > > +++ b/arch/x86/kernel/fpu/init.c > > @@ -38,7 +38,7 @@ static void fpu__init_cpu_generic(void) > > /* Flush out any pending x87 state: */ > > #ifdef CONFIG_MATH_EMULATION > > if (!boot_cpu_has(X86_FEATURE_FPU)) > > - fpstate_init_soft(¤t->thread.fpu.fpstate->regs.soft); > > + fpstate_init_soft(current->thread.fpu->fpstate->regs.soft); > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > Typo? it should be > > ¤t->thread.fpu->fpstate->regs.soft Thx, fixed. > > > +static struct fpu x86_init_fpu __read_mostly; > > + > > static void __init fpu__init_system_early_generic(void) > > { > > + { > > + int this_cpu = smp_processor_id(); > > + > > + fpstate_reset(&x86_init_fpu); > > + current->thread.fpu = &x86_init_fpu; > > + per_cpu(fpu_fpregs_owner_ctx, this_cpu) = &x86_init_fpu; > > + x86_init_fpu.last_cpu = this_cpu; > > + } > > Can't x86_init_fpu be declared inside the block above? As a function-local static? I think globals are better defined in a visible fashion, not hidden among local variables where they are easy to overlook. But the extra block is unnecessary in any case. > > void __init fpu__init_system(void) > > { > > - fpstate_reset(¤t->thread.fpu); > > fpu__init_system_early_generic(); > > + fpstate_reset(current->thread.fpu); > > It seems that fpstate_reset(current->thread.fpu) is not needed after the > change in fpu__init_system_early_generic() above. Yeah. Something like the delta patch below? Thanks, Ingo =================> arch/x86/kernel/fpu/init.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index f9412d012191..de618ec509aa 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -38,7 +38,7 @@ static void fpu__init_cpu_generic(void) /* Flush out any pending x87 state: */ #ifdef CONFIG_MATH_EMULATION if (!boot_cpu_has(X86_FEATURE_FPU)) - fpstate_init_soft(current->thread.fpu->fpstate->regs.soft); + fpstate_init_soft(¤t->thread.fpu->fpstate->regs.soft); else #endif asm volatile ("fninit"); @@ -75,14 +75,12 @@ static struct fpu x86_init_fpu __read_mostly; static void __init fpu__init_system_early_generic(void) { - { - int this_cpu = smp_processor_id(); + int this_cpu = smp_processor_id(); - fpstate_reset(&x86_init_fpu); - current->thread.fpu = &x86_init_fpu; - per_cpu(fpu_fpregs_owner_ctx, this_cpu) = &x86_init_fpu; - x86_init_fpu.last_cpu = this_cpu; - } + fpstate_reset(&x86_init_fpu); + current->thread.fpu = &x86_init_fpu; + per_cpu(fpu_fpregs_owner_ctx, this_cpu) = &x86_init_fpu; + x86_init_fpu.last_cpu = this_cpu; if (!boot_cpu_has(X86_FEATURE_CPUID) && !test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) { @@ -222,7 +220,6 @@ static void __init fpu__init_system_xstate_size_legacy(void) void __init fpu__init_system(void) { fpu__init_system_early_generic(); - fpstate_reset(current->thread.fpu); /* * The FPU has to be operational for some of the