Commit 7c4cb60e authored by Zachary Amsden's avatar Zachary Amsden Committed by Linus Torvalds
Browse files

[PATCH] x86: GDT alignment fix 



Make GDT page aligned and page padded to support running inside of a
hypervisor.  This prevents false sharing of the GDT page with other hot
data, which is not allowed in Xen, and causes performance problems in
VMware.

Rather than go back to the old method of statically allocating the GDT
(which wastes unneded space for non-present CPUs), the GDT for APs is
allocated dynamically.

Signed-off-by: default avatarZachary Amsden <zach@vmware.com>
Cc: "Seth, Rohit" <rohit.seth@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 599a6e8c

arch/i386/kernel/apm.c

+2 −0
Original line number Diff line number Diff line
@@ -2317,6 +2317,8 @@ static int __init apm_init(void) 


	for (i = 0; i < NR_CPUS; i++) {

		struct desc_struct *gdt = get_cpu_gdt_table(i);

  		if (!gdt)

  			continue;

		set_base(gdt[APM_CS >> 3],

			 __va((unsigned long)apm_info.bios.cseg << 4));

		set_base(gdt[APM_CS_16 >> 3],

arch/i386/kernel/cpu/common.c

+0 −3
Original line number Diff line number Diff line
@@ -18,9 +18,6 @@ 


#include "cpu.h"



DEFINE_PER_CPU(struct desc_struct, cpu_gdt_table[GDT_ENTRIES]);

EXPORT_PER_CPU_SYMBOL(cpu_gdt_table);



DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);

EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);

arch/i386/kernel/head.S

+2 −0
Original line number Diff line number Diff line
@@ -525,3 +525,5 @@ ENTRY(cpu_gdt_table) 
	.quad 0x0000000000000000	/* 0xf0 - unused */

	.quad 0x0000000000000000	/* 0xf8 - GDT entry 31: double-fault TSS */



	/* Be sure this is zeroed to avoid false validations in Xen */

	.fill PAGE_SIZE_asm / 8 - GDT_ENTRIES,8,0

arch/i386/kernel/i386_ksyms.c

+1 −2
Original line number Diff line number Diff line
@@ -3,8 +3,7 @@ 
#include <asm/checksum.h>

#include <asm/desc.h>



/* This is definitely a GPL-only symbol */

EXPORT_SYMBOL_GPL(cpu_gdt_table);

EXPORT_SYMBOL_GPL(cpu_gdt_descr);



EXPORT_SYMBOL(__down_failed);

EXPORT_SYMBOL(__down_failed_interruptible);

arch/i386/kernel/smpboot.c

+6 −0
Original line number Diff line number Diff line
@@ -903,6 +903,12 @@ static int __devinit do_boot_cpu(int apicid, int cpu) 
	unsigned long start_eip;

	unsigned short nmi_high = 0, nmi_low = 0;



	if (!cpu_gdt_descr[cpu].address &&

	    !(cpu_gdt_descr[cpu].address = get_zeroed_page(GFP_KERNEL))) {

		printk("Failed to allocate GDT for CPU %d\n", cpu);

		return 1;

	}



	++cpucount;



	/*

CRA Git | Maintained and supported by SUSTech CRA and CCSE