* [RFC] framework for fpu usage in kernel
@ 2001-02-11 19:03 Manfred Spraul
2001-02-11 20:26 ` Alan Cox
0 siblings, 1 reply; 4+ messages in thread
From: Manfred Spraul @ 2001-02-11 19:03 UTC (permalink / raw)
To: linux-kernel, Arjan van de Ven, Doug Ledford, Linus Torvalds
[-- Attachment #1: Type: text/plain, Size: 1728 bytes --]
Currently there are 2 fpu users in the kernel:
raid5 checksumming and 3dnow memcpy/memset.
raid5 checksumming is not problematic, but _mmx_memcpy() has unexpected
side effects if someone else is also using the fpu:
memcopy is a really generic function, and calling it saves the current
fpu state into thread.i387.f{,x}save. IMHO that's wrong, memcopy must
save into a local buffer like raid5 checksumming.
I've attached a proposal that supports arbitrary combinations of fpu
users in kernel space.
* kernel threads can use the fpu freely. Nothing new.
* 2 sets of functions for fpu usage in "normal" threads:
- kfpu_acquire(), kfpu_try_acquire() + release functions.
- kfpu_full_begin(), kfpu_mmx_begin(), kfpu_nosave_begin(),
kfpu_try_begin() + _end() functions.
The first set is only possible from normal process context. The caller
can sleep between _acquire() and _release().
The second set can be called from arbitrary context, but the caller must
not sleep between _begin() and _end().
The _try() functions check if the fpu is unused, and fail if the fpu is
currently in use. That way the memcpy()/memset() functions can avoid fpu
context saves/restores and it saves stack space.
Nesting is partially possible: _begin() within _acquire is possible,
_acquire() within _begin() will BUG.
[_acquire()/_release() have similar restrictions as down() and up(),
_begin()/_end() have similar restrictions as spinlocks]
The patch itself is alpha quality: only the sse functions are tested, it
boots when compiled for Pentium III, the raid5 checksum _benchmark_
still works and distributed.net still cracks rc5.
I haven't yet checked that the exception handlers are still called
properly.
What do you think?
--
Manfred
[-- Attachment #2: patch-kfpu --]
[-- Type: text/plain, Size: 20435 bytes --]
// $Header$
// Kernel Version:
// VERSION = 2
// PATCHLEVEL = 4
// SUBLEVEL = 1
// EXTRAVERSION =
diff -urN 2.4/include/asm-i386/i387.h build-2.4/include/asm-i386/i387.h
--- 2.4/include/asm-i386/i387.h Fri Feb 2 15:20:36 2001
+++ build-2.4/include/asm-i386/i387.h Sun Feb 11 19:40:45 2001
@@ -16,6 +16,7 @@
#include <asm/sigcontext.h>
#include <asm/user.h>
+#include <asm/kfpu.h>
extern void init_fpu(void);
/*
* FPU lazy state save handling...
@@ -23,9 +24,7 @@
extern void save_init_fpu( struct task_struct *tsk );
extern void restore_fpu( struct task_struct *tsk );
-extern void kernel_fpu_begin(void);
-#define kernel_fpu_end() stts()
-
+#include <asm/kfpu.h>
#define unlazy_fpu( tsk ) do { \
if ( tsk->flags & PF_USEDFPU ) \
@@ -36,7 +35,7 @@
if ( tsk->flags & PF_USEDFPU ) { \
asm volatile("fwait"); \
tsk->flags &= ~PF_USEDFPU; \
- stts(); \
+ kfpu_leave(); \
} \
} while (0)
diff -urN 2.4/include/asm-i386/kfpu.h build-2.4/include/asm-i386/kfpu.h
--- 2.4/include/asm-i386/kfpu.h Thu Jan 1 01:00:00 1970
+++ build-2.4/include/asm-i386/kfpu.h Sun Feb 11 19:59:51 2001
@@ -0,0 +1,83 @@
+#ifndef _ASM_KFPU_H
+#define _ASM_KFPU_H
+
+/*
+ * FPU support for kernel threads
+ *
+ * currently limited to MMX, SSE and SSE2.
+ * x87 and fpu emulation are not supported.
+ */
+
+/**********************************/
+/*
+ * Enable full fpu access.
+ * Only for kernel threads.
+ */
+void kfpu_start(void);
+
+
+/**********************************/
+/*
+ * Get full fpu access.
+ *
+ * Only permitted from process context.
+ * Caller must check that the FPU is present before calling.
+ */
+struct kfpubuf_acquire {
+ unsigned long saved;
+ unsigned char buffer[512+16];
+} kfpubuf_acquire;
+
+void kfpu_acquire(struct kfpubuf_acquire *buf);
+void kfpu_release(struct kfpubuf_acquire *buf);
+
+/* returns 1 if it got fpu access, 0 otherwise */
+int kfpu_try_acquire(void);
+void kfpu_try_release(void);
+
+
+/**********************************/
+/*
+ * Get short term fpu access.
+ *
+ * The functions can be called from any context (process,
+ * softirq, interrupt)
+ * Caller must check that the FPU is present before calling.
+ * The caller must not sleep between _begin() and _end()
+ */
+struct kfpubuf_full {
+ unsigned char buffer[512];
+};
+
+struct kfpubuf_mmx {
+ unsigned char buffer[108];
+};
+
+void kfpu_full_begin(struct kfpubuf_full *buf);
+void kfpu_mmx_begin(struct kfpubuf_mmx *buf);
+/*
+ * ret val 0: caller doesn't need to save clobbered regs
+ * ret val !0: the caller must save & restore any clobbered
+ * fpu registers.
+ * This function DOES NOT reinitialize the fpu!
+ */
+int kfpu_nosave_begin(void);
+
+void kfpu_full_end(struct kfpubuf_full *buf);
+void kfpu_mmx_end(struct kfpubuf_mmx *buf);
+void kfpu_nosave_end(void);
+
+/* returns 1 if it got fpu access */
+int kfpu_try_begin(void);
+void kfpu_try_end(void);
+
+/**********************************/
+
+/* internal function, called by math_state_restore() */
+void kfpu_enter(void);
+/* internal function, called by save_init_fpu() */
+void kfpu_leave(void);
+/* internal function, called by cpu_init() */
+void kfpu_initialize(void);
+
+#endif
diff -urN 2.4/include/asm-i386/page.h build-2.4/include/asm-i386/page.h
--- 2.4/include/asm-i386/page.h Thu Jan 4 23:50:46 2001
+++ build-2.4/include/asm-i386/page.h Sun Feb 11 13:10:17 2001
@@ -11,7 +11,14 @@
#include <linux/config.h>
-#ifdef CONFIG_X86_USE_3DNOW
+#ifdef CONFIG_X86_USE_SSE
+
+#include <asm/sse.h>
+
+#define clear_page(page) sse_clear_page(page)
+#define copy_page(to,from) sse_copy_page(to,from)
+
+#elif defined(CONFIG_X86_USE_3DNOW)
#include <asm/mmx.h>
diff -urN 2.4/include/asm-i386/sse.h build-2.4/include/asm-i386/sse.h
--- 2.4/include/asm-i386/sse.h Thu Jan 1 01:00:00 1970
+++ build-2.4/include/asm-i386/sse.h Sun Feb 11 12:59:43 2001
@@ -0,0 +1,11 @@
+#ifndef _ASM_SSE_H
+#define _ASM_SSE_H
+
+/*
+ * SSE helper operations
+ */
+
+extern void sse_clear_page(void *page);
+extern void sse_copy_page(void *to, void *from);
+
+#endif
diff -urN 2.4/include/asm-i386/system.h build-2.4/include/asm-i386/system.h
--- 2.4/include/asm-i386/system.h Sun Feb 11 00:39:07 2001
+++ build-2.4/include/asm-i386/system.h Sun Feb 11 12:41:01 2001
@@ -100,7 +100,6 @@
/*
* Clear and set 'TS' bit respectively
*/
-#define clts() __asm__ __volatile__ ("clts")
#define read_cr0() ({ \
unsigned int __dummy; \
__asm__( \
@@ -110,7 +109,6 @@
})
#define write_cr0(x) \
__asm__("movl %0,%%cr0": :"r" (x));
-#define stts() write_cr0(8 | read_cr0())
#endif /* __KERNEL__ */
diff -urN 2.4/include/asm-i386/xor.h build-2.4/include/asm-i386/xor.h
--- 2.4/include/asm-i386/xor.h Mon Nov 13 04:39:51 2000
+++ build-2.4/include/asm-i386/xor.h Sun Feb 11 19:37:24 2001
@@ -18,18 +18,16 @@
* Copyright (C) 1998 Ingo Molnar.
*/
+#include <asm/kfpu.h>
+
#define FPU_SAVE \
do { \
- if (!(current->flags & PF_USEDFPU)) \
- __asm__ __volatile__ (" clts;\n"); \
- __asm__ __volatile__ ("fsave %0; fwait": "=m"(fpu_save[0])); \
+ kfpu_mmx_begin(&fpu_save); \
} while (0)
#define FPU_RESTORE \
do { \
- __asm__ __volatile__ ("frstor %0": : "m"(fpu_save[0])); \
- if (!(current->flags & PF_USEDFPU)) \
- stts(); \
+ kfpu_mmx_end(&fpu_save); \
} while (0)
#define LD(x,y) " movq 8*("#x")(%1), %%mm"#y" ;\n"
@@ -44,7 +42,7 @@
xor_pII_mmx_2(unsigned long bytes, unsigned long *p1, unsigned long *p2)
{
unsigned long lines = bytes >> 7;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -89,7 +87,7 @@
unsigned long *p3)
{
unsigned long lines = bytes >> 7;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -139,7 +137,7 @@
unsigned long *p3, unsigned long *p4)
{
unsigned long lines = bytes >> 7;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -194,7 +192,7 @@
unsigned long *p3, unsigned long *p4, unsigned long *p5)
{
unsigned long lines = bytes >> 7;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -261,7 +259,7 @@
xor_p5_mmx_2(unsigned long bytes, unsigned long *p1, unsigned long *p2)
{
unsigned long lines = bytes >> 6;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -310,7 +308,7 @@
unsigned long *p3)
{
unsigned long lines = bytes >> 6;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -368,7 +366,7 @@
unsigned long *p3, unsigned long *p4)
{
unsigned long lines = bytes >> 6;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -435,7 +433,7 @@
unsigned long *p3, unsigned long *p4, unsigned long *p5)
{
unsigned long lines = bytes >> 6;
- char fpu_save[108];
+ struct kfpubuf_mmx fpu_save;
FPU_SAVE;
@@ -531,28 +529,31 @@
*/
#define XMMS_SAVE \
- __asm__ __volatile__ ( \
- "movl %%cr0,%0 ;\n\t" \
- "clts ;\n\t" \
- "movups %%xmm0,(%1) ;\n\t" \
- "movups %%xmm1,0x10(%1) ;\n\t" \
- "movups %%xmm2,0x20(%1) ;\n\t" \
- "movups %%xmm3,0x30(%1) ;\n\t" \
- : "=r" (cr0) \
+ restore = kfpu_nosave_begin(); \
+ if (restore) \
+ __asm__ __volatile__ ( \
+ "movups %%xmm0,(%0) ;\n\t" \
+ "movups %%xmm1,0x10(%0) ;\n\t" \
+ "movups %%xmm2,0x20(%0) ;\n\t" \
+ "movups %%xmm3,0x30(%0) ;\n\t" \
+ : /* no output */ \
: "r" (xmm_save) \
: "memory")
#define XMMS_RESTORE \
- __asm__ __volatile__ ( \
- "sfence ;\n\t" \
- "movups (%1),%%xmm0 ;\n\t" \
- "movups 0x10(%1),%%xmm1 ;\n\t" \
- "movups 0x20(%1),%%xmm2 ;\n\t" \
- "movups 0x30(%1),%%xmm3 ;\n\t" \
- "movl %0,%%cr0 ;\n\t" \
- : \
- : "r" (cr0), "r" (xmm_save) \
- : "memory")
+ __asm__ __volatile__ ( \
+ "sfence\n\t" \
+ : : : "memory"); \
+ if (restore) \
+ __asm__ __volatile__ ( \
+ "movups (%0),%%xmm0 ;\n\t" \
+ "movups 0x10(%0),%%xmm1 ;\n\t" \
+ "movups 0x20(%0),%%xmm2 ;\n\t" \
+ "movups 0x30(%0),%%xmm3 ;\n\t" \
+ : /* no output */ \
+ : "r" (xmm_save) \
+ : "memory"); \
+ kfpu_nosave_end()
#define OFFS(x) "16*("#x")"
#define PF0(x) " prefetcht0 "OFFS(x)"(%1) ;\n"
@@ -575,7 +576,7 @@
{
unsigned long lines = bytes >> 8;
char xmm_save[16*4];
- int cr0;
+ int restore;
XMMS_SAVE;
@@ -629,7 +630,7 @@
{
unsigned long lines = bytes >> 8;
char xmm_save[16*4];
- int cr0;
+ int restore;
XMMS_SAVE;
@@ -690,7 +691,7 @@
{
unsigned long lines = bytes >> 8;
char xmm_save[16*4];
- int cr0;
+ int restore;
XMMS_SAVE;
@@ -758,7 +759,7 @@
{
unsigned long lines = bytes >> 8;
char xmm_save[16*4];
- int cr0;
+ int restore;
XMMS_SAVE;
diff -urN --exclude .depend 2.4/arch/i386/lib/Makefile build-2.4/arch/i386/lib/Makefile
--- 2.4/arch/i386/lib/Makefile Sun Feb 11 00:37:51 2001
+++ build-2.4/arch/i386/lib/Makefile Sun Feb 11 12:59:43 2001
@@ -12,6 +12,7 @@
memcpy.o
obj-$(CONFIG_X86_USE_3DNOW) += mmx.o
+obj-$(CONFIG_X86_USE_SSE) += sse.o
obj-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
include $(TOPDIR)/Rules.make
diff -urN --exclude .depend 2.4/arch/i386/lib/mmx.c build-2.4/arch/i386/lib/mmx.c
--- 2.4/arch/i386/lib/mmx.c Sat Feb 3 14:02:24 2001
+++ build-2.4/arch/i386/lib/mmx.c Sun Feb 11 19:28:12 2001
@@ -28,7 +28,11 @@
void *p=to;
int i= len >> 6; /* len/64 */
- kernel_fpu_begin();
+ if(!kfpu_try_begin() {
+ /* FIXME: this belongs into string.h */
+ __memcpy(to, from, len);
+ return;
+ }
__asm__ __volatile__ (
"1: prefetch (%0)\n" /* This set is 28 bytes */
@@ -84,7 +88,7 @@
* Now do the tail of the block
*/
__memcpy(to, from, len&63);
- kernel_fpu_end();
+ kfpu_try_end();
return p;
}
@@ -92,8 +96,6 @@
{
int i;
- kernel_fpu_begin();
-
__asm__ __volatile__ (
" pxor %%mm0, %%mm0\n" : :
);
@@ -118,18 +120,12 @@
__asm__ __volatile__ (
" sfence \n" : :
);
- kernel_fpu_end();
}
static void fast_copy_page(void *to, void *from)
{
int i;
- kernel_fpu_begin();
-
- /* maybe the prefetch stuff can go before the expensive fnsave...
- * but that is for later. -AV
- */
__asm__ __volatile__ (
"1: prefetch (%0)\n"
" prefetch 64(%0)\n"
@@ -185,7 +181,6 @@
__asm__ __volatile__ (
" sfence \n" : :
);
- kernel_fpu_end();
}
/*
@@ -205,10 +200,12 @@
void mmx_clear_page(void * page)
{
- if(in_interrupt())
- slow_zero_page(page);
- else
+ if (kfpu_try_begin()) {
fast_clear_page(page);
+ kfpu_try_end();
+ } else {
+ slow_zero_page(page);
+ }
}
static void slow_copy_page(void *to, void *from)
@@ -225,8 +222,10 @@
void mmx_copy_page(void *to, void *from)
{
- if(in_interrupt())
- slow_copy_page(to, from);
- else
+ if (kfpu_try_begin()) {
fast_copy_page(to, from);
+ kfpu_try_end();
+ } else {
+ slow_copy_page(to, from);
+ }
}
diff -urN --exclude .depend 2.4/arch/i386/lib/sse.c build-2.4/arch/i386/lib/sse.c
--- 2.4/arch/i386/lib/sse.c Thu Jan 1 01:00:00 1970
+++ build-2.4/arch/i386/lib/sse.c Sun Feb 11 18:02:30 2001
@@ -0,0 +1,107 @@
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/sched.h>
+
+#include <asm/i387.h>
+
+/*
+ * SSE library helper functions
+ *
+ * Copyright (C) 2001 Manfred Spraul
+ *
+ * Based on Intel sample code from
+ * Block Copy Using Pentium(R) III Streaming SIMD Extensions
+ * Revision 1.9
+ * January 12, 1999
+ *
+ */
+
+
+void sse_clear_page(void * page)
+{
+ int storage[4];
+ int restore;
+ int d0;
+ restore = kfpu_nosave_begin();
+ if (restore) {
+ __asm__ __volatile__(
+ "movups %%xmm0, (%0)\n\t"
+ : /* no output */
+ : "r" (&storage[0])
+ : "memory" );
+ }
+ __asm__ __volatile__(
+ "xorps %%xmm0, %%xmm0\n\t"
+ "xor %0, %0\n\t"
+ "1: movntps %%xmm0, (%1)\n\t"
+ "movntps %%xmm0, 16(%1)\n\t"
+ "add $32, %1\n\t"
+ "inc %0\n\t"
+ "cmp $128, %0\n\t"
+ "jne 1b\n\t"
+ "sfence\n\t"
+ : "=&r" (d0), "=&r" (page)
+ : "1" (page)
+ : "cc", "memory");
+ if (restore) {
+ __asm__ __volatile__(
+ "movups (%0), %%xmm0\n\t"
+ : /* no output */
+ : "r" (&storage[0])
+ : "memory" );
+ }
+ kfpu_nosave_end();
+}
+
+void sse_copy_page(void *to, void *from)
+{
+ int storage[16];
+ int restore;
+ int d0;
+ restore = kfpu_nosave_begin();
+ if (restore) {
+ __asm__ __volatile__(
+ "movups %%xmm0, (%0)\n\t"
+ "movups %%xmm1, 16(%0)\n\t"
+ "movups %%xmm2, 32(%0)\n\t"
+ "movups %%xmm3, 48(%0)\n\t"
+ : /* no output */
+ : "r" (&storage[0])
+ : "memory" );
+ }
+ __asm__ __volatile__(
+ "mov (%2), %0\n\t" /* step 1: load the TLB */
+ "xor %0, %0\n\t" /* step 2: prefetch the page */
+ "1:prefetchnta (%2, %0)\n\t"
+ "prefetchnta 32(%2, %0)\n\t"
+ "add $64,%0\n\t"
+ "cmp $4096, %0\n\t"
+ "jne 1b\n\t"
+ "2: movaps (%2), %%xmm0\n\t" /* step 3: copy the page */
+ "movaps 16(%2), %%xmm1\n\t"
+ "movaps 32(%2), %%xmm2\n\t"
+ "movaps 48(%2), %%xmm3\n\t"
+ "add $64, %2\n\t"
+ "movntps %%xmm0, (%1)\n\t"
+ "movntps %%xmm1, 16(%1)\n\t"
+ "movntps %%xmm2, 32(%1)\n\t"
+ "movntps %%xmm3, 48(%1)\n\t"
+ "add $64, %1\n\t"
+ "sub $64, %0\n\t"
+ "jnz 2b\n\t"
+ "sfence\n\t"
+ : "=&r" (d0), "=&r" (to), "=&r" (from)
+ : "1" (to), "2" (from)
+ : "cc", "memory");
+ if (restore) {
+ __asm__ __volatile__(
+ "movups (%0), %%xmm0\n\t"
+ "movups 16(%0), %%xmm1\n\t"
+ "movups 32(%0), %%xmm2\n\t"
+ "movups 48(%0), %%xmm3\n\t"
+ : /* no output */
+ : "r" (&storage[0])
+ : "memory" );
+ }
+ kfpu_nosave_end();
+}
--- 2.4/arch/i386/kernel/i387.c Sun Feb 11 00:37:51 2001
+++ build-2.4/arch/i386/kernel/i387.c Sun Feb 11 19:35:49 2001
@@ -24,6 +24,8 @@
#define HAVE_HWFP 1
#endif
+static volatile int cpu_fpuactive[NR_CPUS];
+
/*
* The _current_ task is using the FPU for the first time
* so initialize it and set the mxcsr to its default
@@ -39,10 +41,19 @@
current->used_math = 1;
}
+void inline stts(void)
+{
+ write_cr0(8 | read_cr0())
+}
+
+char *sse_aligned(char *buffer)
+{
+ return (char*)((((unsigned long)buffer)+15)&(~15));
+}
+
/*
* FPU lazy state save handling.
*/
-
static inline void __save_init_fpu( struct task_struct *tsk )
{
if ( cpu_has_fxsr ) {
@@ -58,18 +69,191 @@
void save_init_fpu( struct task_struct *tsk )
{
__save_init_fpu(tsk);
- stts();
+ kfpu_leave();
+}
+
+void kfpu_start(void)
+{
+ if ( cpu_has_fpu ) {
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts"); /* Allow maths ops (or we recurse) */
+ init_fpu();
+ current->flags |= PF_USEDFPU; /* So we fnsave on switch_to() */
+ current->used_math = 1;
+ }
}
-void kernel_fpu_begin(void)
+void kfpu_acquire(struct kfpubuf_acquire *buf)
{
- struct task_struct *tsk = current;
+ if (!current->used_math) {
+ buf->saved = 0;
+ kfpu_try_acquire();
+ return;
+ }
+ buf->saved = 1;
+ unlazy_fpu(current);
+ if ( cpu_has_fxsr ) {
+ memcpy(buf->buffer, ¤t->thread.i387.fxsave,
+ sizeof(current->thread.i387.fxsave));
+ } else {
+ memcpy(buf->buffer, ¤t->thread.i387.fsave,
+ sizeof(current->thread.i387.fsave));
+ }
+
+ if (cpu_fpuactive[smp_processor_id()])
+ BUG();
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ init_fpu();
+ current->flags |= PF_USEDFPU;
+}
- if (tsk->flags & PF_USEDFPU) {
- __save_init_fpu(tsk);
+void kfpu_release(struct kfpubuf_acquire *buf)
+{
+ if (!buf->saved) {
+ kfpu_try_release();
return;
}
- clts();
+ clear_fpu(current);
+ if ( cpu_has_fxsr ) {
+ memcpy(¤t->thread.i387.fxsave, buf->buffer,
+ sizeof(current->thread.i387.fxsave));
+ } else {
+ memcpy(¤t->thread.i387.fsave, buf->buffer,
+ sizeof(current->thread.i387.fsave));
+ }
+ if (cpu_fpuactive[smp_processor_id()])
+ BUG();
+ if (current->flags & PF_USEDFPU)
+ BUG();
+}
+
+/* returns 1 if it got fpu access, 0 otherwise */
+int kfpu_try_acquire(void)
+{
+ if (current->used_math)
+ return 0;
+ current->used_math = 1;
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ init_fpu();
+ current->flags |= PF_USEDFPU;
+ return 1;
+}
+
+void kfpu_try_release(void)
+{
+ clear_fpu(current);
+ current->used_math = 0;
+ if (cpu_fpuactive[smp_processor_id()])
+ BUG();
+ if (current->flags & PF_USEDFPU)
+ BUG();
+}
+
+void kfpu_full_begin(struct kfpubuf_full *buf)
+{
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ if(cpu_fpuactive[smp_processor_id()] > 1) {
+ char *buffer = sse_aligned(buffer);
+ asm volatile( "fxsave %0 ; fnclex"
+ : "=m" (buffer) );
+ }
+ __asm__("fninit");
+ load_mxcsr(0x1f80);
+}
+
+void kfpu_mmx_begin(struct kfpubuf_mmx *buf)
+{
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ if(cpu_fpuactive[smp_processor_id()] > 1) {
+ asm volatile( "fnsave %0 ; fwait"
+ : "=m" (buf->buffer) );
+ }
+ __asm__("fninit");
+}
+
+/* ret val 0: caller doesn't need to save clobbered regs */
+int kfpu_nosave_begin(void)
+{
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ return cpu_fpuactive[smp_processor_id()]-1;
+}
+
+void kfpu_full_end(struct kfpubuf_full *buf)
+{
+ if(cpu_fpuactive[smp_processor_id()] > 1) {
+ char *buffer = sse_aligned(buffer);
+ asm volatile( "fxrstor %0"
+ : "=m" (buffer) );
+ cpu_fpuactive[smp_processor_id()]--;
+ } else {
+ cpu_fpuactive[smp_processor_id()]--;
+ stts();
+ }
+}
+
+void kfpu_mmx_end(struct kfpubuf_mmx *buf)
+{
+ if(cpu_fpuactive[smp_processor_id()] > 1) {
+ asm volatile( "frstor %0"
+ : "=m" (buf->buffer) );
+ cpu_fpuactive[smp_processor_id()]--;
+ } else {
+ cpu_fpuactive[smp_processor_id()]--;
+ stts();
+ }
+}
+
+void kfpu_nosave_end(void)
+{
+ cpu_fpuactive[smp_processor_id()]--;
+ if(cpu_fpuactive[smp_processor_id()] == 0)
+ stts();
+}
+
+/* returns 1 if it got fpu access */
+int kfpu_try_begin(void)
+{
+ if (cpu_fpuactive[smp_processor_id()] > 0)
+ return 0;
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+ __asm__("fninit");
+ if ( cpu_has_xmm )
+ load_mxcsr(0x1f80);
+ return 1;
+}
+
+void kfpu_try_end(void)
+{
+ cpu_fpuactive[smp_processor_id()]--;
+ stts();
+}
+
+void kfpu_initialize(void)
+{
+ cpu_fpuactive[smp_processor_id()] = 0;
+ stts();
+}
+
+void kfpu_enter(void)
+{
+ if(cpu_fpuactive[smp_processor_id()] != 0)
+ BUG();
+ cpu_fpuactive[smp_processor_id()]++;
+ __asm__ __volatile__("clts");
+}
+
+void kfpu_leave(void)
+{
+ cpu_fpuactive[smp_processor_id()]--;
+ stts();
+ if(cpu_fpuactive[smp_processor_id()] != 0)
+ BUG();
}
void restore_fpu( struct task_struct *tsk )
--- 2.4/arch/i386/kernel/traps.c Sun Feb 11 00:37:51 2001
+++ build-2.4/arch/i386/kernel/traps.c Sun Feb 11 19:18:59 2001
@@ -731,7 +731,7 @@
*/
asmlinkage void math_state_restore(struct pt_regs regs)
{
- __asm__ __volatile__("clts"); /* Allow maths ops (or we recurse) */
+ kfpu_enter(); /* Allow maths ops (or we recurse) */
if (current->used_math) {
restore_fpu(current);
--- 2.4/arch/i386/kernel/setup.c Sun Feb 11 00:37:51 2001
+++ build-2.4/arch/i386/kernel/setup.c Sun Feb 11 14:33:58 2001
@@ -2274,7 +2274,8 @@
*/
current->flags &= ~PF_USEDFPU;
current->used_math = 0;
- stts();
+ kfpu_initialize();
+
}
/*
--- 2.4/arch/i386/kernel/i386_ksyms.c Sun Feb 11 00:37:51 2001
+++ build-2.4/arch/i386/kernel/i386_ksyms.c Sun Feb 11 19:25:05 2001
@@ -117,6 +117,25 @@
EXPORT_SYMBOL(mmx_copy_page);
#endif
+#ifdef CONFIG_X86_USE_SSE
+EXPORT_SYMBOL(sse_clear_page);
+EXPORT_SYMBOL(sse_copy_page);
+#endif
+
+EXPORT_SYMBOL(kfpu_start);
+EXPORT_SYMBOL(kfpu_acquire);
+EXPORT_SYMBOL(kfpu_release);
+EXPORT_SYMBOL(kfpu_try_acquire);
+EXPORT_SYMBOL(kfpu_try_release);
+EXPORT_SYMBOL(kfpu_full_begin);
+EXPORT_SYMBOL(kfpu_mmx_begin);
+EXPORT_SYMBOL(kfpu_nosave_begin);
+EXPORT_SYMBOL(kfpu_full_end);
+EXPORT_SYMBOL(kfpu_mmx_end);
+EXPORT_SYMBOL(kfpu_nosave_end);
+EXPORT_SYMBOL(kfpu_try_begin);
+EXPORT_SYMBOL(kfpu_try_end);
+
#ifdef CONFIG_SMP
EXPORT_SYMBOL(cpu_data);
EXPORT_SYMBOL(kernel_flag);
--- 2.4/arch/i386/config.in Sun Feb 11 00:37:50 2001
+++ build-2.4/arch/i386/config.in Sun Feb 11 19:18:59 2001
@@ -91,6 +91,7 @@
define_bool CONFIG_X86_GOOD_APIC y
define_bool CONFIG_X86_PGE y
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
+ define_bool CONFIG_X86_USE_SSE y
fi
if [ "$CONFIG_MPENTIUM4" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 7
@@ -98,6 +99,7 @@
define_bool CONFIG_X86_GOOD_APIC y
define_bool CONFIG_X86_PGE y
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
+ define_bool CONFIG_X86_USE_SSE y
fi
if [ "$CONFIG_MK6" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 5
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC] framework for fpu usage in kernel
2001-02-11 19:03 [RFC] framework for fpu usage in kernel Manfred Spraul
@ 2001-02-11 20:26 ` Alan Cox
2001-02-11 20:30 ` Manfred Spraul
0 siblings, 1 reply; 4+ messages in thread
From: Alan Cox @ 2001-02-11 20:26 UTC (permalink / raw)
To: Manfred Spraul
Cc: linux-kernel, Arjan van de Ven, Doug Ledford, Linus Torvalds
> memcopy is a really generic function, and calling it saves the current
> fpu state into thread.i387.f{,x}save. IMHO that's wrong, memcopy must
> save into a local buffer like raid5 checksumming.
The mmx copy is only done in task context. There are a whole variety
of _horrible_ problems doing it in interrupt space so based on the
considerable number of problems with prior attempts to get it right on
IRQ and copyuser cases I didnt bother
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC] framework for fpu usage in kernel
2001-02-11 20:26 ` Alan Cox
@ 2001-02-11 20:30 ` Manfred Spraul
2001-02-11 20:37 ` Alan Cox
0 siblings, 1 reply; 4+ messages in thread
From: Manfred Spraul @ 2001-02-11 20:30 UTC (permalink / raw)
To: Alan Cox; +Cc: linux-kernel, Arjan van de Ven, Doug Ledford, Linus Torvalds
Alan Cox wrote:
>
> > memcopy is a really generic function, and calling it saves the current
> > fpu state into thread.i387.f{,x}save. IMHO that's wrong, memcopy must
> > save into a local buffer like raid5 checksumming.
>
> The mmx copy is only done in task context. There are a whole variety
> of _horrible_ problems doing it in interrupt space so based on the
> considerable number of problems with prior attempts to get it right on
> IRQ and copyuser cases I didnt bother
>
Even task context is dangerous:
What if a drm module wants to use the fpu and then uses memcpy() after
modifying the ftp registers?
--
Manfred
-
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the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2001-02-11 20:38 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2001-02-11 19:03 [RFC] framework for fpu usage in kernel Manfred Spraul
2001-02-11 20:26 ` Alan Cox
2001-02-11 20:30 ` Manfred Spraul
2001-02-11 20:37 ` Alan Cox
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