[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>
diff --git a/include/asm-i386/elf.h b/include/asm-i386/elf.h
index 369035d..8d33c9b 100644
--- a/include/asm-i386/elf.h
+++ b/include/asm-i386/elf.h
@@ -90,8 +90,8 @@
pr_reg[6] = regs->eax; \
pr_reg[7] = regs->xds; \
pr_reg[8] = regs->xes; \
- savesegment(fs,pr_reg[9]); \
- pr_reg[10] = regs->xgs; \
+ pr_reg[9] = regs->xfs; \
+ savesegment(gs,pr_reg[10]); \
pr_reg[11] = regs->orig_eax; \
pr_reg[12] = regs->eip; \
pr_reg[13] = regs->xcs; \
diff --git a/include/asm-i386/mmu_context.h b/include/asm-i386/mmu_context.h
index 68ff102..e6aa30f 100644
--- a/include/asm-i386/mmu_context.h
+++ b/include/asm-i386/mmu_context.h
@@ -63,7 +63,7 @@
}
#define deactivate_mm(tsk, mm) \
- asm("movl %0,%%fs": :"r" (0));
+ asm("movl %0,%%gs": :"r" (0));
#define activate_mm(prev, next) \
switch_mm((prev),(next),NULL)
diff --git a/include/asm-i386/pda.h b/include/asm-i386/pda.h
index 2ba2736..b12d59a 100644
--- a/include/asm-i386/pda.h
+++ b/include/asm-i386/pda.h
@@ -39,19 +39,19 @@
if (0) { T__ tmp__; tmp__ = (val); } \
switch (sizeof(_proxy_pda.field)) { \
case 1: \
- asm(op "b %1,%%gs:%c2" \
+ asm(op "b %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
break; \
case 2: \
- asm(op "w %1,%%gs:%c2" \
+ asm(op "w %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
break; \
case 4: \
- asm(op "l %1,%%gs:%c2" \
+ asm(op "l %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
@@ -65,19 +65,19 @@
typeof(_proxy_pda.field) ret__; \
switch (sizeof(_proxy_pda.field)) { \
case 1: \
- asm(op "b %%gs:%c1,%0" \
+ asm(op "b %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \
break; \
case 2: \
- asm(op "w %%gs:%c1,%0" \
+ asm(op "w %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \
break; \
case 4: \
- asm(op "l %%gs:%c1,%0" \
+ asm(op "l %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \
diff --git a/include/asm-i386/processor.h b/include/asm-i386/processor.h
index 359f10b..11bf899 100644
--- a/include/asm-i386/processor.h
+++ b/include/asm-i386/processor.h
@@ -424,7 +424,7 @@
.vm86_info = NULL, \
.sysenter_cs = __KERNEL_CS, \
.io_bitmap_ptr = NULL, \
- .gs = __KERNEL_PDA, \
+ .fs = __KERNEL_PDA, \
}
/*
@@ -442,8 +442,8 @@
}
#define start_thread(regs, new_eip, new_esp) do { \
- __asm__("movl %0,%%fs": :"r" (0)); \
- regs->xgs = 0; \
+ __asm__("movl %0,%%gs": :"r" (0)); \
+ regs->xfs = 0; \
set_fs(USER_DS); \
regs->xds = __USER_DS; \
regs->xes = __USER_DS; \
diff --git a/include/asm-i386/ptrace.h b/include/asm-i386/ptrace.h
index bdbc894..1646996 100644
--- a/include/asm-i386/ptrace.h
+++ b/include/asm-i386/ptrace.h
@@ -16,8 +16,8 @@
long eax;
int xds;
int xes;
- /* int xfs; */
- int xgs;
+ int xfs;
+ /* int xgs; */
long orig_eax;
long eip;
int xcs;