Linux x86 SIMD: factor out unneeded kernel dependencies

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 #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 <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Attila Fülöp <[email protected]>
Closes #13102 

1 files changed, 6 insertions, 99 deletions

diff --git a/config/kernel-fpu.m4 b/config/kernel-fpu.m4
index 7f8b028d0..eb9520c60 100644
--- a/config/kernel-fpu.m4
+++ b/config/kernel-fpu.m4
@@ -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 #
@@ -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)
 	])
 ])
 
@@ -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();
@@ -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], [
@@ -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])
 		])
 	])
 ])