aboutsummaryrefslogtreecommitdiff
path: root/arch/i386/math-emu
diff options
context:
space:
mode:
authorJeremy Fitzhardinge <jeremy@goop.org>2007-02-13 13:26:20 +0100
committerAndi Kleen <andi@basil.nowhere.org>2007-02-13 13:26:20 +0100
commit464d1a78fbf8cf6c7fd970e7b3e2db50a320ce28 (patch)
tree536d8a92976e675b484b35dec88d40c97fab8ac8 /arch/i386/math-emu
parent54413927f022292aeccadd268fbf1c0b42129945 (diff)
[PATCH] i386: Convert i386 PDA code to use %fs
Convert the PDA code to use %fs rather than %gs as the segment for per-processor data. This is because some processors show a small but measurable performance gain for reloading a NULL segment selector (as %fs generally is in user-space) versus a non-NULL one (as %gs generally is). On modern processors the difference is very small, perhaps undetectable. Some old AMD "K6 3D+" processors are noticably slower when %fs is used rather than %gs; I have no idea why this might be, but I think they're sufficiently rare that it doesn't matter much. This patch also fixes the math emulator, which had not been adjusted to match the changed struct pt_regs. [frederik.deweerdt@gmail.com: fixit with gdb] [mingo@elte.hu: Fix KVM too] Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Ian Campbell <Ian.Campbell@XenSource.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Zachary Amsden <zach@vmware.com> Cc: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org>
Diffstat (limited to 'arch/i386/math-emu')
-rw-r--r--arch/i386/math-emu/get_address.c14
1 files changed, 5 insertions, 9 deletions
diff --git a/arch/i386/math-emu/get_address.c b/arch/i386/math-emu/get_address.c
index 9819b705efa..2e2c51a8bd3 100644
--- a/arch/i386/math-emu/get_address.c
+++ b/arch/i386/math-emu/get_address.c
@@ -56,15 +56,14 @@ static int reg_offset_vm86[] = {
#define VM86_REG_(x) (*(unsigned short *) \
(reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
-/* These are dummy, fs and gs are not saved on the stack. */
-#define ___FS ___ds
+/* This dummy, gs is not saved on the stack. */
#define ___GS ___ds
static int reg_offset_pm[] = {
offsetof(struct info,___cs),
offsetof(struct info,___ds),
offsetof(struct info,___es),
- offsetof(struct info,___FS),
+ offsetof(struct info,___fs),
offsetof(struct info,___GS),
offsetof(struct info,___ss),
offsetof(struct info,___ds)
@@ -169,13 +168,10 @@ static long pm_address(u_char FPU_modrm, u_char segment,
switch ( segment )
{
- /* fs and gs aren't used by the kernel, so they still have their
- user-space values. */
- case PREFIX_FS_-1:
- /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
- savesegment(fs, addr->selector);
- break;
+ /* gs isn't used by the kernel, so it still has its
+ user-space value. */
case PREFIX_GS_-1:
+ /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
savesegment(gs, addr->selector);
break;
default: