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x86/fpu: Document the various fpregs state formats

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Document all the structures that make up 'struct fpu'.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-05-02 10:22:45 +02:00
parent aeb997b9f2
commit bdf80d1040
1 changed files with 33 additions and 2 deletions
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33
arch/x86/include/asm/fpu/types.h
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@ -4,6 +4,10 @@
#ifndef _ASM_X86_FPU_H
#define _ASM_X86_FPU_H
/*
* The legacy x87 FPU state format, as saved by FSAVE and
* restored by the FRSTOR instructions:
*/
struct fregs_state {
u32 cwd; /* FPU Control Word */
u32 swd; /* FPU Status Word */
@ -20,6 +24,12 @@ struct fregs_state {
u32 status;
};
/*
* The legacy fx SSE/MMX FPU state format, as saved by FXSAVE and
* restored by the FXRSTOR instructions. It's similar to the FSAVE
* format, but differs in some areas, plus has extensions at
* the end for the XMM registers.
*/
struct fxregs_state {
u16 cwd; /* Control Word */
u16 swd; /* Status Word */
@ -56,7 +66,8 @@ struct fxregs_state {
} __attribute__((aligned(16)));
/*
* Software based FPU emulation state:
* Software based FPU emulation state. This is arbitrary really,
* it matches the x87 format to make it easier to understand:
*/
struct swregs_state {
u32 cwd;
@ -140,6 +151,14 @@ struct xstate_header {
u64 reserved[6];
} __attribute__((packed));
/*
* This is our most modern FPU state format, as saved by the XSAVE
* and restored by the XRSTOR instructions.
*
* It consists of a legacy fxregs portion, an xstate header and
* subsequent fixed size areas as defined by the xstate header.
* Not all CPUs support all the extensions.
*/
struct xregs_state {
struct fxregs_state i387;
struct xstate_header header;
@ -150,6 +169,13 @@ struct xregs_state {
/* New processor state extensions will go here. */
} __attribute__ ((packed, aligned (64)));
/*
* This is a union of all the possible FPU state formats
* put together, so that we can pick the right one runtime.
*
* The size of the structure is determined by the largest
* member - which is the xsave area:
*/
union fpregs_state {
struct fregs_state fsave;
struct fxregs_state fxsave;
@ -157,6 +183,11 @@ union fpregs_state {
struct xregs_state xsave;
};
/*
* Highest level per task FPU state data structure that
* contains the FPU register state plus various FPU
* state fields:
*/
struct fpu {
/*
* @state: