linuxkpi: add kernel_fpu_begin/kernel_fpu_end

With newer AMD GPUs (>=Navi,Renoir) there is FPU context usage in the
amdgpu driver.
The `kernel_fpu_begin/end` implementations in drm did not even allow nested
begin-end blocks.

Submitted by: Greg V
Reviewed By: manu, hselasky
Differential Revision: https://reviews.freebsd.org/D28061

sys/compat/linuxkpi/common/include/asm/fpu/api.h

@@ -0,0 +1,68 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * 
+ * Copyright (c) 2020 Greg V <greg@unrelenting.technology>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef	_FPU_API_H_
+#define	_FPU_API_H_
+
+#if defined(__aarch64__) || defined(__amd64__) || defined(__i386__)
+
+#include <machine/fpu.h>
+
+extern struct fpu_kern_ctx *__lkpi_fpu_ctx;
+extern unsigned int __lkpi_fpu_ctx_level;
+
+static inline void
+kernel_fpu_begin()
+{
+	if (__lkpi_fpu_ctx_level++ == 0) {
+		fpu_kern_enter(curthread, __lkpi_fpu_ctx, FPU_KERN_NORMAL);
+	}
+}
+
+static inline void
+kernel_fpu_end()
+{
+	if (--__lkpi_fpu_ctx_level == 0) {
+		fpu_kern_leave(curthread, __lkpi_fpu_ctx);
+	}
+}
+
+#else
+
+static inline void
+kernel_fpu_begin()
+{
+}
+
+static inline void
+kernel_fpu_end()
+{
+}
+
+#endif
+
+#endif /* _FPU_API_H_ */

sys/compat/linuxkpi/common/src/linux_fpu.c

@@ -0,0 +1,50 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ * 
+ * Copyright (c) 2020 Greg V <greg@unrelenting.technology>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/proc.h>
+#include <sys/kernel.h>
+
+#include <machine/fpu.h>
+
+struct fpu_kern_ctx *__lkpi_fpu_ctx;
+unsigned int __lkpi_fpu_ctx_level = 0;
+
+static void
+linux_fpu_init(void *arg __unused)
+{
+	__lkpi_fpu_ctx = fpu_kern_alloc_ctx(0);
+}
+SYSINIT(linux_fpu, SI_SUB_EVENTHANDLER, SI_ORDER_SECOND, linux_fpu_init, NULL);
+
+static void
+linux_fpu_uninit(void *arg __unused)
+{
+	fpu_kern_free_ctx(__lkpi_fpu_ctx);
+}
+SYSUNINIT(linux_fpu, SI_SUB_EVENTHANDLER, SI_ORDER_SECOND, linux_fpu_uninit, NULL);

sys/conf/files.amd64

@@ -462,6 +462,9 @@ x86/xen/pv.c			optional	xenhvm
 x86/xen/pvcpu_enum.c		optional	xenhvm
 x86/xen/xen_pci_bus.c		optional	xenhvm
 
+compat/linuxkpi/common/src/linux_fpu.c		optional compat_linuxkpi \
+	compile-with "${LINUXKPI_C}"
+
 contrib/openzfs/module/zcommon/zfs_fletcher_avx512.c		optional zfs compile-with "${ZFS_C}"
 contrib/openzfs/module/zcommon/zfs_fletcher_intel.c		optional zfs compile-with "${ZFS_C}"
 contrib/openzfs/module/zcommon/zfs_fletcher_sse.c		optional zfs compile-with "${ZFS_C}"

sys/conf/files.arm64

@@ -494,3 +494,6 @@ tegra210_xusb.fw	optional	tegra210_xusb_fw		\
 	compile-with	"${NORMAL_FW}"					\
 	no-obj no-implicit-rule						\
 	clean		"tegra210_xusb.fw"
+
+compat/linuxkpi/common/src/linux_fpu.c		optional compat_linuxkpi \
+	compile-with "${LINUXKPI_C}"

sys/conf/files.i386

@@ -241,3 +241,6 @@ x86/x86/local_apic.c		optional apic
 x86/x86/mptable.c		optional apic
 x86/x86/mptable_pci.c		optional apic pci
 x86/x86/msi.c			optional apic pci
+
+compat/linuxkpi/common/src/linux_fpu.c		optional compat_linuxkpi \
+	compile-with "${LINUXKPI_C}"

sys/modules/linuxkpi/Makefile

@@ -26,7 +26,7 @@ SRCS=	linux_compat.c \
 
 .if ${MACHINE_CPUARCH} == "aarch64" || ${MACHINE_CPUARCH} == "amd64" || \
     ${MACHINE_CPUARCH} == "i386"
-SRCS+=	opt_acpi.h acpi_if.h linux_acpi.c
+SRCS+=	opt_acpi.h acpi_if.h linux_acpi.c linux_fpu.c
 .endif
 
 SRCS+=	${LINUXKPI_GENSRCS}