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Linux 4.14, 4.19, 5.0+ compat: SIMD save/restore

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Contrary to initial testing we cannot rely on these kernels to
invalidate the per-cpu FPU state and restore the FPU registers.
Nor can we guarantee that the kernel won't modify the FPU state
which we saved in the task struck.

Therefore, the kfpu_begin() and kfpu_end() functions have been
updated to save and restore the FPU state using our own dedicated
per-cpu FPU state variables.

This has the additional advantage of allowing us to use the FPU
again in user threads.  So we remove the code which was added to
use task queues to ensure some functions ran in kernel threads.

Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #9346
Closes #9403
This commit is contained in:
Brian Behlendorf
2019-10-24 10:17:33 -07:00
committed by GitHub
parent b834b58ae6
commit 10fa254539
19 changed files with 276 additions and 294 deletions
Download Patch File Download Diff File Expand all files Collapse all files
config/kernel-fpu.m4
+41 -39
View File
@@ -2,15 +2,9 @@ dnl #
dnl # Handle differences in kernel FPU code.
dnl #
dnl # Kernel
dnl # 5.2: The fpu->initialized flag was replaced by TIF_NEED_FPU_LOAD.
dnl # HAVE_KERNEL_TIF_NEED_FPU_LOAD
dnl #
dnl # 5.0: As an optimization SIMD operations performed by kernel
dnl # threads can skip saving and restoring their FPU context.
dnl # Wrappers have been introduced to determine the running
dnl # context and use either the SIMD or generic implementation.
dnl # 5.0: Wrappers have been introduced to save/restore the FPU state.
dnl # This change was made to the 4.19.38 and 4.14.120 LTS kernels.
dnl # HAVE_KERNEL_FPU_INITIALIZED
dnl # HAVE_KERNEL_FPU_INTERNAL
dnl #
dnl # 4.2: Use __kernel_fpu_{begin,end}()
dnl # HAVE_UNDERSCORE_KERNEL_FPU & KERNEL_EXPORTS_X86_FPU
@@ -38,6 +32,7 @@ AC_DEFUN([ZFS_AC_KERNEL_FPU_HEADER], [
AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
ZFS_LINUX_TEST_SRC([kernel_fpu], [
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#else
@@ -50,6 +45,7 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
], [], [$ZFS_META_LICENSE])
ZFS_LINUX_TEST_SRC([__kernel_fpu], [
#include <linux/types.h>
#ifdef HAVE_KERNEL_FPU_API_HEADER
#include <asm/fpu/api.h>
#else
@@ -61,22 +57,41 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
__kernel_fpu_end();
], [], [$ZFS_META_LICENSE])
ZFS_LINUX_TEST_SRC([fpu_initialized], [
#include <linux/module.h>
#include <linux/sched.h>
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;
if (fpu->initialized) { return (0); };
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([tif_need_fpu_load], [
#include <linux/module.h>
#include <asm/thread_info.h>
#if !defined(TIF_NEED_FPU_LOAD)
#error "TIF_NEED_FPU_LOAD undefined"
#endif
],[])
])
AC_DEFUN([ZFS_AC_KERNEL_FPU], [
@@ -104,25 +119,12 @@ AC_DEFUN([ZFS_AC_KERNEL_FPU], [
AC_DEFINE(KERNEL_EXPORTS_X86_FPU, 1,
[kernel exports FPU functions])
],[
dnl #
dnl # Linux 5.0 kernel
dnl #
ZFS_LINUX_TEST_RESULT([fpu_initialized], [
AC_MSG_RESULT(fpu.initialized)
AC_DEFINE(HAVE_KERNEL_FPU_INITIALIZED, 1,
[kernel fpu.initialized exists])
ZFS_LINUX_TEST_RESULT([fpu_internal], [
AC_MSG_RESULT(internal)
AC_DEFINE(HAVE_KERNEL_FPU_INTERNAL, 1,
[kernel fpu internal])
],[
dnl #
dnl # Linux 5.2 kernel
dnl #
ZFS_LINUX_TEST_RESULT([tif_need_fpu_load], [
AC_MSG_RESULT(TIF_NEED_FPU_LOAD)
AC_DEFINE(
HAVE_KERNEL_TIF_NEED_FPU_LOAD, 1,
[kernel TIF_NEED_FPU_LOAD exists])
],[
AC_MSG_RESULT(unavailable)
])
AC_MSG_RESULT(unavailable)
])
])
])