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Message-ID: <20240612184148.GB23973@redhat.com>
Date: Wed, 12 Jun 2024 20:41:48 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave@...1.net>, Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
"H . Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Uros Bizjak <ubizjak@...il.com>
Subject: Re: [PATCH 3/9] x86/fpu: Make task_struct::thread constant size
The patch below seems to fix the problem.
Again, the changes in fpu__init_system_early_generic() are not
strictly needed to fix it, but I believe make sense anyway.
Oleg.
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 4e8d37b5a90b..848ea79886ba 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -71,16 +71,14 @@ static bool __init fpu__probe_without_cpuid(void)
return fsw == 0 && (fcw & 0x103f) == 0x003f;
}
-static struct fpu x86_init_fpu __read_mostly;
+static struct fpu x86_init_fpu __attribute__ ((aligned (64))) __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;
+ set_thread_flag(TIF_NEED_FPU_LOAD);
+ x86_init_fpu.last_cpu = -1;
if (!boot_cpu_has(X86_FEATURE_CPUID) &&
!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 215a7380e41c..ec22b9bf27f5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1562,7 +1562,7 @@ struct task_struct {
* they are included in the randomized portion of task_struct.
*/
randomized_struct_fields_end
-};
+} __attribute__ ((aligned (64)));
#define TASK_REPORT_IDLE (TASK_REPORT + 1)
#define TASK_REPORT_MAX (TASK_REPORT_IDLE << 1)
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