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Linux x86 SIMD: factor out unneeded kernel dependencies
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Cleanup the kernel SIMD code by removing kernel dependencies.

 - Replace XSTATE_XSAVE with our own XSAVE implementation for all
   kernels not exporting kernel_fpu{begin,end}(), see openzfs#13059

 - Replace union fpregs_state by a uint8_t * buffer and get the size
   of the buffer from the hardware via the CPUID instruction

 - Replace kernels xgetbv() by our own implementation which was
   already there for userspace.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes openzfs#13102
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@AttilaFueloep @andrewc12
AttilaFueloep authored and andrewc12 committed Aug 30, 2022
1 parent aecf6e8 commit c7b51a9
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Showing 3 changed files with 117 additions and 239 deletions.
105 changes: 6 additions & 99 deletions config/kernel-fpu.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,6 @@ dnl #
dnl # Handle differences in kernel FPU code.
dnl #
dnl # Kernel
dnl # 5.16: XCR code put into asm/fpu/xcr.h
dnl # HAVE_KERNEL_FPU_XCR_HEADER
dnl #
dnl # XSTATE_XSAVE and XSTATE_XRESTORE aren't accessible any more
dnl # HAVE_KERNEL_FPU_XSAVE_INTERNAL
dnl #
dnl # 5.11: kernel_fpu_begin() is an inlined function now, so don't check
dnl # for it inside the kernel symbols.
dnl #
Expand All @@ -34,20 +28,8 @@ AC_DEFUN([ZFS_AC_KERNEL_FPU_HEADER], [
AC_DEFINE(HAVE_KERNEL_FPU_API_HEADER, 1,
[kernel has asm/fpu/api.h])
AC_MSG_RESULT(asm/fpu/api.h)
AC_MSG_CHECKING([whether fpu/xcr header is available])
ZFS_LINUX_TRY_COMPILE([
#include <linux/module.h>
#include <asm/fpu/xcr.h>
],[
],[
AC_DEFINE(HAVE_KERNEL_FPU_XCR_HEADER, 1,
[kernel has asm/fpu/xcr.h])
AC_MSG_RESULT(asm/fpu/xcr.h)
],[
AC_MSG_RESULT(no asm/fpu/xcr.h)
])
],[
AC_MSG_RESULT(i387.h & xcr.h)
AC_MSG_RESULT(i387.h)
])
])

Expand All @@ -56,9 +38,9 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#else
#include <asm/i387.h>
#include <asm/xcr.h>
#endif
], [
kernel_fpu_begin();
Expand All @@ -69,80 +51,15 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#else
#include <asm/i387.h>
#include <asm/xcr.h>
#endif
], [
__kernel_fpu_begin();
__kernel_fpu_end();
], [], [ZFS_META_LICENSE])
ZFS_LINUX_TEST_SRC([fpu_internal], [
#if defined(__x86_64) || defined(__x86_64__) || \
defined(__i386) || defined(__i386__)
#if !defined(__x86)
#define __x86
#endif
#endif
#if !defined(__x86)
#error Unsupported architecture
#endif
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#else
#include <asm/i387.h>
#include <asm/xcr.h>
#endif
#if !defined(XSTATE_XSAVE)
#error XSTATE_XSAVE not defined
#endif
#if !defined(XSTATE_XRESTORE)
#error XSTATE_XRESTORE not defined
#endif
],[
struct fpu *fpu = &current->thread.fpu;
union fpregs_state *st = &fpu->state;
struct fregs_state *fr __attribute__ ((unused)) = &st->fsave;
struct fxregs_state *fxr __attribute__ ((unused)) = &st->fxsave;
struct xregs_state *xr __attribute__ ((unused)) = &st->xsave;
])
ZFS_LINUX_TEST_SRC([fpu_xsave_internal], [
#include <linux/sched.h>
#if defined(__x86_64) || defined(__x86_64__) || \
defined(__i386) || defined(__i386__)
#if !defined(__x86)
#define __x86
#endif
#endif
#if !defined(__x86)
#error Unsupported architecture
#endif
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
#else
#include <asm/i387.h>
#include <asm/xcr.h>
#endif
],[
struct fpu *fpu = &current->thread.fpu;
union fpregs_state *st = &fpu->fpstate->regs;
struct fregs_state *fr __attribute__ ((unused)) = &st->fsave;
struct fxregs_state *fxr __attribute__ ((unused)) = &st->fxsave;
struct xregs_state *xr __attribute__ ((unused)) = &st->xsave;
])
])

AC_DEFUN([ZFS_AC_KERNEL_FPU], [
Expand All @@ -169,19 +86,9 @@ AC_DEFUN([ZFS_AC_KERNEL_FPU], [
AC_DEFINE(KERNEL_EXPORTS_X86_FPU, 1,
[kernel exports FPU functions])
],[
ZFS_LINUX_TEST_RESULT([fpu_internal], [
AC_MSG_RESULT(internal)
AC_DEFINE(HAVE_KERNEL_FPU_INTERNAL, 1,
[kernel fpu internal])
],[
ZFS_LINUX_TEST_RESULT([fpu_xsave_internal], [
AC_MSG_RESULT(internal with internal XSAVE)
AC_DEFINE(HAVE_KERNEL_FPU_XSAVE_INTERNAL, 1,
[kernel fpu and XSAVE internal])
],[
AC_MSG_RESULT(unavailable)
])
])
AC_MSG_RESULT(internal)
AC_DEFINE(HAVE_KERNEL_FPU_INTERNAL, 1,
[kernel fpu internal])
])
])
])
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