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Linux 5.16 compat: don't use XSTATE_XSAVE to save FPU state

Browse Source 
Linux 5.16 moved XSTATE_XSAVE and XSTATE_XRESTORE out of our reach,
so add our own XSAVE{,OPT,S} code and use it for Linux 5.16.

Please note that this differs from previous behavior in that it
won't handle exceptions created by XSAVE an XRSTOR. This is sensible
for three reasons.

 - Exceptions during XSAVE and XRSTOR can only occur if the feature
   is not supported or enabled or the memory operand isn't aligned
   on a 64 byte boundary. If this happens something else went
   terribly wrong, and it may be better to stop execution.

 - Previously we just printed a warning and didn't handle the fault,
   this is arguable for the above reason.

 - All other *SAVE instruction also don't handle exceptions, so this
   at least aligns behavior.

Finally add a test to catch such a regression in the future.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes #13042
Closes #13059
This commit is contained in:
Attila Fülöp 2022-02-09 21:50:10 +01:00 committed by Tony Hutter
parent bb271d67e8
commit 3b52ccd7d7
9 changed files with 300 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
config/kernel-fpu.m4
View File

@ -1,9 +1,12 @@
dnl #
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 # 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 # 5.0: 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.
@ -107,6 +110,36 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_FPU], [
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], [
@ -139,7 +172,13 @@ AC_DEFUN([ZFS_AC_KERNEL_FPU], [
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)
])
])
])
])

66
config/toolchain-simd.m4
View File

@ -24,6 +24,9 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_TOOLCHAIN_SIMD], [
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_AES
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_PCLMULQDQ
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_MOVBE
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVE
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVEOPT
ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVES
;;
esac
])
@ -422,3 +425,66 @@ AC_DEFUN([ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_MOVBE], [
AC_MSG_RESULT([no])
])
])
dnl #
dnl # ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVE
dnl #
AC_DEFUN([ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVE], [
AC_MSG_CHECKING([whether host toolchain supports XSAVE])
AC_LINK_IFELSE([AC_LANG_SOURCE([
[
void main()
{
char b[4096] __attribute__ ((aligned (64)));
__asm__ __volatile__("xsave %[b]\n" : : [b] "m" (*b) : "memory");
}
]])], [
AC_MSG_RESULT([yes])
AC_DEFINE([HAVE_XSAVE], 1, [Define if host toolchain supports XSAVE])
], [
AC_MSG_RESULT([no])
])
])
dnl #
dnl # ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVEOPT
dnl #
AC_DEFUN([ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVEOPT], [
AC_MSG_CHECKING([whether host toolchain supports XSAVEOPT])
AC_LINK_IFELSE([AC_LANG_SOURCE([
[
void main()
{
char b[4096] __attribute__ ((aligned (64)));
__asm__ __volatile__("xsaveopt %[b]\n" : : [b] "m" (*b) : "memory");
}
]])], [
AC_MSG_RESULT([yes])
AC_DEFINE([HAVE_XSAVEOPT], 1, [Define if host toolchain supports XSAVEOPT])
], [
AC_MSG_RESULT([no])
])
])
dnl #
dnl # ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVES
dnl #
AC_DEFUN([ZFS_AC_CONFIG_TOOLCHAIN_CAN_BUILD_XSAVES], [
AC_MSG_CHECKING([whether host toolchain supports XSAVES])
AC_LINK_IFELSE([AC_LANG_SOURCE([
[
void main()
{
char b[4096] __attribute__ ((aligned (64)));
__asm__ __volatile__("xsaves %[b]\n" : : [b] "m" (*b) : "memory");
}
]])], [
AC_MSG_RESULT([yes])
AC_DEFINE([HAVE_XSAVES], 1, [Define if host toolchain supports XSAVES])
], [
AC_MSG_RESULT([no])
])
])

1
configure.ac
View File

@ -383,6 +383,7 @@ AC_CONFIG_FILES([
tests/zfs-tests/tests/functional/rootpool/Makefile
tests/zfs-tests/tests/functional/rsend/Makefile
tests/zfs-tests/tests/functional/scrub_mirror/Makefile
tests/zfs-tests/tests/functional/simd/Makefile
tests/zfs-tests/tests/functional/slog/Makefile
tests/zfs-tests/tests/functional/snapshot/Makefile
tests/zfs-tests/tests/functional/snapused/Makefile

125
include/os/linux/kernel/linux/simd_x86.h
View File

@ -136,9 +136,27 @@
* When the kernel_fpu_* symbols are unavailable then provide our own
* versions which allow the FPU to be safely used.
*/
#if defined(HAVE_KERNEL_FPU_INTERNAL) || defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
#if defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
/*
* Some sanity checks.
* HAVE_KERNEL_FPU_INTERNAL and HAVE_KERNEL_FPU_XSAVE_INTERNAL are exclusive.
*/
#if defined(HAVE_KERNEL_FPU_INTERNAL)
#error "HAVE_KERNEL_FPU_INTERNAL and HAVE_KERNEL_FPU_XSAVE_INTERNAL defined"
#endif
/*
* For kernels >= 5.16 we have to use inline assembly with the XSAVE{,OPT,S}
* instructions, so we need the toolchain to support at least XSAVE.
*/
#if !defined(HAVE_XSAVE)
#error "Toolchain needs to support the XSAVE assembler instruction"
#endif
#endif
#include <linux/mm.h>
#include <linux/slab.h>
extern union fpregs_state **zfs_kfpu_fpregs;
@ -191,7 +209,9 @@ kfpu_init(void)
}
#define kfpu_allowed() 1
#if defined(HAVE_KERNEL_FPU_INTERNAL)
#define ex_handler_fprestore ex_handler_default
#endif
/*
* FPU save and restore instructions.
@ -206,6 +226,7 @@ kfpu_init(void)
#define kfpu_fxsr_clean(rval) __asm("fnclex; emms; fildl %P[addr]" \
: : [addr] "m" (rval));
#if defined(HAVE_KERNEL_FPU_INTERNAL)
static inline void
kfpu_save_xsave(struct xregs_state *addr, uint64_t mask)
{
@ -217,6 +238,21 @@ kfpu_save_xsave(struct xregs_state *addr, uint64_t mask)
XSTATE_XSAVE(addr, low, hi, err);
WARN_ON_ONCE(err);
}
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL) */
#if defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
#define kfpu_do_xsave(instruction, addr, mask) \
{ \
uint32_t low, hi; \
\
low = mask; \
hi = (uint64_t)(mask) >> 32; \
__asm(instruction " %[dst]\n\t" \
: \
: [dst] "m" (*(addr)), "a" (low), "d" (hi) \
: "memory"); \
}
#endif /* defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL) */
static inline void
kfpu_save_fxsr(struct fxregs_state *addr)
@ -233,6 +269,7 @@ kfpu_save_fsave(struct fregs_state *addr)
kfpu_fnsave(addr);
}
#if defined(HAVE_KERNEL_FPU_INTERNAL)
static inline void
kfpu_begin(void)
{
@ -250,7 +287,6 @@ kfpu_begin(void)
* FPU state to be correctly preserved and restored.
*/
union fpregs_state *state = zfs_kfpu_fpregs[smp_processor_id()];
if (static_cpu_has(X86_FEATURE_XSAVE)) {
kfpu_save_xsave(&state->xsave, ~0);
} else if (static_cpu_has(X86_FEATURE_FXSR)) {
@ -259,7 +295,50 @@ kfpu_begin(void)
kfpu_save_fsave(&state->fsave);
}
}
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL) */
#if defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
static inline void
kfpu_begin(void)
{
/*
* Preemption and interrupts must be disabled for the critical
* region where the FPU state is being modified.
*/
preempt_disable();
local_irq_disable();
/*
* The current FPU registers need to be preserved by kfpu_begin()
* and restored by kfpu_end(). They are stored in a dedicated
* per-cpu variable, not in the task struct, this allows any user
* FPU state to be correctly preserved and restored.
*/
union fpregs_state *state = zfs_kfpu_fpregs[smp_processor_id()];
#if defined(HAVE_XSAVES)
if (static_cpu_has(X86_FEATURE_XSAVES)) {
kfpu_do_xsave("xsaves", &state->xsave, ~0);
goto out;
}
#endif
#if defined(HAVE_XSAVEOPT)
if (static_cpu_has(X86_FEATURE_XSAVEOPT)) {
kfpu_do_xsave("xsaveopt", &state->xsave, ~0);
goto out;
}
#endif
if (static_cpu_has(X86_FEATURE_XSAVE)) {
kfpu_do_xsave("xsave", &state->xsave, ~0);
} else if (static_cpu_has(X86_FEATURE_FXSR)) {
kfpu_save_fxsr(&state->fxsave);
} else {
kfpu_save_fsave(&state->fsave);
}
out:
}
#endif /* defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL) */
#if defined(HAVE_KERNEL_FPU_INTERNAL)
static inline void
kfpu_restore_xsave(struct xregs_state *addr, uint64_t mask)
{
@ -269,6 +348,21 @@ kfpu_restore_xsave(struct xregs_state *addr, uint64_t mask)
hi = mask >> 32;
XSTATE_XRESTORE(addr, low, hi);
}
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL) */
#if defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
#define kfpu_do_xrstor(instruction, addr, mask) \
{ \
uint32_t low, hi; \
\
low = mask; \
hi = (uint64_t)(mask) >> 32; \
__asm(instruction " %[src]" \
: \
: [src] "m" (*(addr)), "a" (low), "d" (hi) \
: "memory"); \
}
#endif /* defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL) */
static inline void
kfpu_restore_fxsr(struct fxregs_state *addr)
@ -294,6 +388,7 @@ kfpu_restore_fsave(struct fregs_state *addr)
kfpu_frstor(addr);
}
#if defined(HAVE_KERNEL_FPU_INTERNAL)
static inline void
kfpu_end(void)
{
@ -310,6 +405,32 @@ kfpu_end(void)
local_irq_enable();
preempt_enable();
}
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL) */
#if defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
static inline void
kfpu_end(void)
{
union fpregs_state *state = zfs_kfpu_fpregs[smp_processor_id()];
#if defined(HAVE_XSAVES)
if (static_cpu_has(X86_FEATURE_XSAVES)) {
kfpu_do_xrstor("xrstors", &state->xsave, ~0);
goto out;
}
#endif
if (static_cpu_has(X86_FEATURE_XSAVE)) {
kfpu_do_xrstor("xrstor", &state->xsave, ~0);
} else if (static_cpu_has(X86_FEATURE_FXSR)) {
kfpu_save_fxsr(&state->fxsave);
} else {
kfpu_save_fsave(&state->fsave);
}
out:
local_irq_enable();
preempt_enable();
}
#endif /* defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL) */
#else
@ -322,7 +443,7 @@ kfpu_end(void)
#define kfpu_init() 0
#define kfpu_fini() ((void) 0)
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL) */
#endif /* defined(HAVE_KERNEL_FPU_INTERNAL || HAVE_KERNEL_FPU_XSAVE_INTERNAL) */
#endif /* defined(KERNEL_EXPORTS_X86_FPU) */
/*

4
module/zcommon/zfs_prop.c
View File

@ -996,10 +996,10 @@ zfs_prop_align_right(zfs_prop_t prop)
#include <sys/simd.h>
#if defined(HAVE_KERNEL_FPU_INTERNAL)
#if defined(HAVE_KERNEL_FPU_INTERNAL) || defined(HAVE_KERNEL_FPU_XSAVE_INTERNAL)
union fpregs_state **zfs_kfpu_fpregs;
EXPORT_SYMBOL(zfs_kfpu_fpregs);
#endif /* HAVE_KERNEL_FPU_INTERNAL */
#endif /* HAVE_KERNEL_FPU_INTERNAL || HAVE_KERNEL_FPU_XSAVE_INTERNAL */
static int __init
zcommon_init(void)

6
tests/runfiles/linux.run
View File

@ -151,6 +151,12 @@ tags = ['functional', 'projectquota']
tests = ['send_realloc_dnode_size', 'send_encrypted_files']
tags = ['functional', 'rsend']
[tests/functional/simd:Linux]
pre =
post =
tests = ['simd_supported']
tags = ['functional', 'simd']
[tests/functional/snapshot:Linux]
tests = ['snapshot_015_pos', 'snapshot_016_pos']
tags = ['functional', 'snapshot']

1
tests/zfs-tests/tests/functional/Makefile.am
View File

@ -88,5 +88,6 @@ SUBDIRS = \
if BUILD_LINUX
SUBDIRS += \
simd \
tmpfile
endif

2
tests/zfs-tests/tests/functional/simd/Makefile.am Normal file
View File

@ -0,0 +1,2 @@
pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/simd
dist_pkgdata_SCRIPTS = simd_supported.ksh

58
tests/zfs-tests/tests/functional/simd/simd_supported.ksh Executable file
View File

@ -0,0 +1,58 @@
#!/bin/ksh -p
#
# CDDL HEADER START
#
# The contents of this file are subject to the terms of the
# Common Development and Distribution License (the "License").
# You may not use this file except in compliance with the License.
#
# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
# or http://www.opensolaris.org/os/licensing.
# See the License for the specific language governing permissions
# and limitations under the License.
#
# When distributing Covered Code, include this CDDL HEADER in each
# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
# If applicable, add the following below this CDDL HEADER, with the
# fields enclosed by brackets "[]" replaced with your own identifying
# information: Portions Copyright [yyyy] [name of copyright owner]
#
# CDDL HEADER END
#
#
# Copyright (c) 2022 by Attila Fülöp <attila@fueloep.org>
#
. $STF_SUITE/include/libtest.shlib
#
# DESCRIPTION:
# Make sure we have SIMD support, so it will not go away without notice
#
# STRATEGY:
# 1. Test if we are running on a Linux x86 system with SSE support
# 2. If so, check if the zfs_fletcher_4_impl module parameter contains
# a sse implementation
# 3. If not fail the test, otherwise pass it
log_note "Testing if we support SIMD instructions (Linux x86 only)"
if !is_linux; then
log_unsupported "Not a Linux System"
fi
case "$(uname -m)" in
i386|i686|x86_64)
typeset -R modparam="/sys/module/zcommon/parameters/zfs_fletcher_4_impl"
if cat /proc/cpuinfo | awk '/^flags/ {print; exit;}' | grep -q sse; then
log_must grep -q sse "$modparam"
log_pass "SIMD instructions supported"
else
log_unsupported "No FPU present"
fi
;;
*)
log_unsupported "Not a x86 CPU"
;;
esac