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x86: Remove CONFIG_X86_OOSTORE
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This was an optimization that made memcpy type benchmarks a little
faster on ancient (Circa 1998) IDT Winchip CPUs.  In real-life
workloads, it wasn't even noticable, and I doubt anyone is running
benchmarks on 16 year old silicon any more.

Given this code has likely seen very little use over the last decade,
let's just remove it.

Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Dave Jones authored and Linus Torvalds committed Mar 11, 2014
1 parent 8712a00 commit 09df7c4
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Showing 6 changed files with 5 additions and 290 deletions.
4 changes: 0 additions & 4 deletions arch/x86/Kconfig.cpu
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Original file line number Diff line number Diff line change
Expand Up @@ -341,10 +341,6 @@ config X86_USE_3DNOW
def_bool y
depends on (MCYRIXIII || MK7 || MGEODE_LX) && !UML

config X86_OOSTORE
def_bool y
depends on (MWINCHIP3D || MWINCHIPC6) && MTRR

#
# P6_NOPs are a relatively minor optimization that require a family >=
# 6 processor, except that it is broken on certain VIA chips.
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8 changes: 2 additions & 6 deletions arch/x86/include/asm/barrier.h
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Expand Up @@ -85,11 +85,7 @@
#else
# define smp_rmb() barrier()
#endif
#ifdef CONFIG_X86_OOSTORE
# define smp_wmb() wmb()
#else
# define smp_wmb() barrier()
#endif
#define smp_wmb() barrier()
#define smp_read_barrier_depends() read_barrier_depends()
#define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
#else /* !SMP */
Expand All @@ -100,7 +96,7 @@
#define set_mb(var, value) do { var = value; barrier(); } while (0)
#endif /* SMP */

#if defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE)
#if defined(CONFIG_X86_PPRO_FENCE)

/*
* For either of these options x86 doesn't have a strong TSO memory
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2 changes: 1 addition & 1 deletion arch/x86/include/asm/io.h
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Expand Up @@ -237,7 +237,7 @@ memcpy_toio(volatile void __iomem *dst, const void *src, size_t count)

static inline void flush_write_buffers(void)
{
#if defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE)
#if defined(CONFIG_X86_PPRO_FENCE)
asm volatile("lock; addl $0,0(%%esp)": : :"memory");
#endif
}
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5 changes: 2 additions & 3 deletions arch/x86/include/asm/spinlock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,10 +26,9 @@
# define LOCK_PTR_REG "D"
#endif

#if defined(CONFIG_X86_32) && \
(defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE))
#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE))
/*
* On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock
* On PPro SMP, we use a locked operation to unlock
* (PPro errata 66, 92)
*/
# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
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272 changes: 0 additions & 272 deletions arch/x86/kernel/cpu/centaur.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,236 +8,6 @@

#include "cpu.h"

#ifdef CONFIG_X86_OOSTORE

static u32 power2(u32 x)
{
u32 s = 1;

while (s <= x)
s <<= 1;

return s >>= 1;
}


/*
* Set up an actual MCR
*/
static void centaur_mcr_insert(int reg, u32 base, u32 size, int key)
{
u32 lo, hi;

hi = base & ~0xFFF;
lo = ~(size-1); /* Size is a power of 2 so this makes a mask */
lo &= ~0xFFF; /* Remove the ctrl value bits */
lo |= key; /* Attribute we wish to set */
wrmsr(reg+MSR_IDT_MCR0, lo, hi);
mtrr_centaur_report_mcr(reg, lo, hi); /* Tell the mtrr driver */
}

/*
* Figure what we can cover with MCR's
*
* Shortcut: We know you can't put 4Gig of RAM on a winchip
*/
static u32 ramtop(void)
{
u32 clip = 0xFFFFFFFFUL;
u32 top = 0;
int i;

for (i = 0; i < e820.nr_map; i++) {
unsigned long start, end;

if (e820.map[i].addr > 0xFFFFFFFFUL)
continue;
/*
* Don't MCR over reserved space. Ignore the ISA hole
* we frob around that catastrophe already
*/
if (e820.map[i].type == E820_RESERVED) {
if (e820.map[i].addr >= 0x100000UL &&
e820.map[i].addr < clip)
clip = e820.map[i].addr;
continue;
}
start = e820.map[i].addr;
end = e820.map[i].addr + e820.map[i].size;
if (start >= end)
continue;
if (end > top)
top = end;
}
/*
* Everything below 'top' should be RAM except for the ISA hole.
* Because of the limited MCR's we want to map NV/ACPI into our
* MCR range for gunk in RAM
*
* Clip might cause us to MCR insufficient RAM but that is an
* acceptable failure mode and should only bite obscure boxes with
* a VESA hole at 15Mb
*
* The second case Clip sometimes kicks in is when the EBDA is marked
* as reserved. Again we fail safe with reasonable results
*/
if (top > clip)
top = clip;

return top;
}

/*
* Compute a set of MCR's to give maximum coverage
*/
static int centaur_mcr_compute(int nr, int key)
{
u32 mem = ramtop();
u32 root = power2(mem);
u32 base = root;
u32 top = root;
u32 floor = 0;
int ct = 0;

while (ct < nr) {
u32 fspace = 0;
u32 high;
u32 low;

/*
* Find the largest block we will fill going upwards
*/
high = power2(mem-top);

/*
* Find the largest block we will fill going downwards
*/
low = base/2;

/*
* Don't fill below 1Mb going downwards as there
* is an ISA hole in the way.
*/
if (base <= 1024*1024)
low = 0;

/*
* See how much space we could cover by filling below
* the ISA hole
*/

if (floor == 0)
fspace = 512*1024;
else if (floor == 512*1024)
fspace = 128*1024;

/* And forget ROM space */

/*
* Now install the largest coverage we get
*/
if (fspace > high && fspace > low) {
centaur_mcr_insert(ct, floor, fspace, key);
floor += fspace;
} else if (high > low) {
centaur_mcr_insert(ct, top, high, key);
top += high;
} else if (low > 0) {
base -= low;
centaur_mcr_insert(ct, base, low, key);
} else
break;
ct++;
}
/*
* We loaded ct values. We now need to set the mask. The caller
* must do this bit.
*/
return ct;
}

static void centaur_create_optimal_mcr(void)
{
int used;
int i;

/*
* Allocate up to 6 mcrs to mark as much of ram as possible
* as write combining and weak write ordered.
*
* To experiment with: Linux never uses stack operations for
* mmio spaces so we could globally enable stack operation wc
*
* Load the registers with type 31 - full write combining, all
* writes weakly ordered.
*/
used = centaur_mcr_compute(6, 31);

/*
* Wipe unused MCRs
*/
for (i = used; i < 8; i++)
wrmsr(MSR_IDT_MCR0+i, 0, 0);
}

static void winchip2_create_optimal_mcr(void)
{
u32 lo, hi;
int used;
int i;

/*
* Allocate up to 6 mcrs to mark as much of ram as possible
* as write combining, weak store ordered.
*
* Load the registers with type 25
* 8 - weak write ordering
* 16 - weak read ordering
* 1 - write combining
*/
used = centaur_mcr_compute(6, 25);

/*
* Mark the registers we are using.
*/
rdmsr(MSR_IDT_MCR_CTRL, lo, hi);
for (i = 0; i < used; i++)
lo |= 1<<(9+i);
wrmsr(MSR_IDT_MCR_CTRL, lo, hi);

/*
* Wipe unused MCRs
*/

for (i = used; i < 8; i++)
wrmsr(MSR_IDT_MCR0+i, 0, 0);
}

/*
* Handle the MCR key on the Winchip 2.
*/
static void winchip2_unprotect_mcr(void)
{
u32 lo, hi;
u32 key;

rdmsr(MSR_IDT_MCR_CTRL, lo, hi);
lo &= ~0x1C0; /* blank bits 8-6 */
key = (lo>>17) & 7;
lo |= key<<6; /* replace with unlock key */
wrmsr(MSR_IDT_MCR_CTRL, lo, hi);
}

static void winchip2_protect_mcr(void)
{
u32 lo, hi;

rdmsr(MSR_IDT_MCR_CTRL, lo, hi);
lo &= ~0x1C0; /* blank bits 8-6 */
wrmsr(MSR_IDT_MCR_CTRL, lo, hi);
}
#endif /* CONFIG_X86_OOSTORE */

#define ACE_PRESENT (1 << 6)
#define ACE_ENABLED (1 << 7)
#define ACE_FCR (1 << 28) /* MSR_VIA_FCR */
Expand Down Expand Up @@ -362,20 +132,6 @@ static void init_centaur(struct cpuinfo_x86 *c)
fcr_clr = DPDC;
printk(KERN_NOTICE "Disabling bugged TSC.\n");
clear_cpu_cap(c, X86_FEATURE_TSC);
#ifdef CONFIG_X86_OOSTORE
centaur_create_optimal_mcr();
/*
* Enable:
* write combining on non-stack, non-string
* write combining on string, all types
* weak write ordering
*
* The C6 original lacks weak read order
*
* Note 0x120 is write only on Winchip 1
*/
wrmsr(MSR_IDT_MCR_CTRL, 0x01F0001F, 0);
#endif
break;
case 8:
switch (c->x86_mask) {
Expand All @@ -392,40 +148,12 @@ static void init_centaur(struct cpuinfo_x86 *c)
fcr_set = ECX8|DSMC|DTLOCK|EMMX|EBRPRED|ERETSTK|
E2MMX|EAMD3D;
fcr_clr = DPDC;
#ifdef CONFIG_X86_OOSTORE
winchip2_unprotect_mcr();
winchip2_create_optimal_mcr();
rdmsr(MSR_IDT_MCR_CTRL, lo, hi);
/*
* Enable:
* write combining on non-stack, non-string
* write combining on string, all types
* weak write ordering
*/
lo |= 31;
wrmsr(MSR_IDT_MCR_CTRL, lo, hi);
winchip2_protect_mcr();
#endif
break;
case 9:
name = "3";
fcr_set = ECX8|DSMC|DTLOCK|EMMX|EBRPRED|ERETSTK|
E2MMX|EAMD3D;
fcr_clr = DPDC;
#ifdef CONFIG_X86_OOSTORE
winchip2_unprotect_mcr();
winchip2_create_optimal_mcr();
rdmsr(MSR_IDT_MCR_CTRL, lo, hi);
/*
* Enable:
* write combining on non-stack, non-string
* write combining on string, all types
* weak write ordering
*/
lo |= 31;
wrmsr(MSR_IDT_MCR_CTRL, lo, hi);
winchip2_protect_mcr();
#endif
break;
default:
name = "??";
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4 changes: 0 additions & 4 deletions arch/x86/um/asm/barrier.h
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Original file line number Diff line number Diff line change
Expand Up @@ -40,11 +40,7 @@
#define smp_rmb() barrier()
#endif /* CONFIG_X86_PPRO_FENCE */

#ifdef CONFIG_X86_OOSTORE
#define smp_wmb() wmb()
#else /* CONFIG_X86_OOSTORE */
#define smp_wmb() barrier()
#endif /* CONFIG_X86_OOSTORE */

#define smp_read_barrier_depends() read_barrier_depends()
#define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
Expand Down

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