linux_dsm_epyc7002/arch/x86/kernel/head32.c
Andy Lutomirski 1e02ce4ccc x86: Store a per-cpu shadow copy of CR4
Context switches and TLB flushes can change individual bits of CR4.
CR4 reads take several cycles, so store a shadow copy of CR4 in a
per-cpu variable.

To avoid wasting a cache line, I added the CR4 shadow to
cpu_tlbstate, which is already touched in switch_mm.  The heaviest
users of the cr4 shadow will be switch_mm and __switch_to_xtra, and
__switch_to_xtra is called shortly after switch_mm during context
switch, so the cacheline is likely to be hot.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Vince Weaver <vince@deater.net>
Cc: "hillf.zj" <hillf.zj@alibaba-inc.com>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/3a54dd3353fffbf84804398e00dfdc5b7c1afd7d.1414190806.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-04 12:10:42 +01:00

52 lines
1.2 KiB
C

/*
* linux/arch/i386/kernel/head32.c -- prepare to run common code
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/init.h>
#include <linux/start_kernel.h>
#include <linux/mm.h>
#include <linux/memblock.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/e820.h>
#include <asm/page.h>
#include <asm/apic.h>
#include <asm/io_apic.h>
#include <asm/bios_ebda.h>
#include <asm/tlbflush.h>
#include <asm/bootparam_utils.h>
static void __init i386_default_early_setup(void)
{
/* Initialize 32bit specific setup functions */
x86_init.resources.reserve_resources = i386_reserve_resources;
x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
reserve_ebda_region();
}
asmlinkage __visible void __init i386_start_kernel(void)
{
cr4_init_shadow();
sanitize_boot_params(&boot_params);
/* Call the subarch specific early setup function */
switch (boot_params.hdr.hardware_subarch) {
case X86_SUBARCH_INTEL_MID:
x86_intel_mid_early_setup();
break;
case X86_SUBARCH_CE4100:
x86_ce4100_early_setup();
break;
default:
i386_default_early_setup();
break;
}
start_kernel();
}