BACKPORT: ARM: 8991/1: use VFP assembler mnemonics if available

commit 2cbd1cc upstream. The integrated assembler of Clang 10 and earlier do not allow to access the VFP registers through the coprocessor load/store instructions: arch/arm/vfp/vfpmodule.c:342:2: error: invalid operand for instruction fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK)); ^ arch/arm/vfp/vfpinstr.h:79:6: note: expanded from macro 'fmxr' asm("mcr p10, 7, %0, " vfpreg(_vfp_) ", cr0, 0 @ fmxr " #_vfp_ ", %0" ^ <inline asm>:1:6: note: instantiated into assembly here mcr p10, 7, r0, cr8, cr0, 0 @ fmxr FPEXC, r0 ^ This has been addressed with Clang 11 [0]. However, to support earlier versions of Clang and for better readability use of VFP assembler mnemonics still is preferred. Ideally we would replace this code with the unified assembler language mnemonics vmrs/vmsr on call sites along with .fpu assembler directives. The GNU assembler supports the .fpu directive at least since 2.17 (when documentation has been added). Since Linux requires binutils 2.21 it is safe to use .fpu directive. However, binutils does not allow to use FPINST or FPINST2 as an argument to vmrs/vmsr instructions up to binutils 2.24 (see binutils commit 16d02dc907c5): arch/arm/vfp/vfphw.S: Assembler messages: arch/arm/vfp/vfphw.S:162: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST,r6' arch/arm/vfp/vfphw.S:165: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST2,r8' arch/arm/vfp/vfphw.S:235: Error: operand 1 must be a VFP extension System Register -- `vmrs r3,FPINST' arch/arm/vfp/vfphw.S:238: Error: operand 1 must be a VFP extension System Register -- `vmrs r12,FPINST2' Use as-instr in Kconfig to check if FPINST/FPINST2 can be used. If they can be used make use of .fpu directives and UAL VFP mnemonics for register access. This allows to build vfpmodule.c with Clang and its integrated assembler. [0] https://reviews.llvm.org/D59733 Link: ClangBuiltLinux/linux#905 Signed-off-by: Stefan Agner <[email protected]> Change-Id: Ibe43b4f40e924759f9a6bca4a7a7ae7cea473077 Signed-off-by: Russell King <[email protected]> [nd: Adjusted hunk from arch/arm/Kconfig due to missing commit 8a90a32 ("arm: Unplug KVM from the build system"). Replace __ACCESS_VFP with fmrx/fmxr for arch/arm/kvm/switch.c. CONFIG_KVM was removed in commit 541ad01 ("arm: Remove 32bit KVM host support") in v5.7.1. CONFIG_KVM is not enabled as part of allmodconfig or alldefconfig, but axm55xx_defconfig explicitly does enable it. Adjusted arch/arm/vfp/vfphw.S due to conflict with commit a47b395 ("ARM: 9030/1: entry: omit FP emulation for UND exceptions taken in kernel mode").] Bug: 141693040 Signed-off-by: Nick Desaulniers <[email protected]> (cherry picked from commit 5208d4f) Signed-off-by: TogoFire <[email protected]>
dev-sm8350 · May 19, 2024 · 5ccca9c · 5ccca9c
1 parent f0fd8f7
commit 5ccca9c
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Showing 12 changed files with 48 additions and 14 deletions.
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
@@ -2167,3 +2167,4 @@ source "arch/arm/crypto/Kconfig"
 endif
 
 source "arch/arm/kvm/Kconfig"
+source "arch/arm/Kconfig.assembler"
diff --git a/arch/arm/Kconfig.assembler b/arch/arm/Kconfig.assembler
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config AS_VFP_VMRS_FPINST
+	def_bool $(as-instr,.fpu vfpv2\nvmrs r0$(comma)FPINST)
+	help
+	  Supported by binutils >= 2.24 and LLVM integrated assembler.
diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
@@ -14,9 +14,6 @@
 
 #define __hyp_text __section(.hyp.text) notrace
 
-#define __ACCESS_VFP(CRn)			\
-	"mrc", "mcr", __stringify(p10, 7, %0, CRn, cr0, 0), u32
-
 #define write_special(v, r)					\
 	asm volatile("msr " __stringify(r) ", %0" : : "r" (v))
 #define read_special(r) ({					\
@@ -79,8 +76,6 @@
 #define CNTV_CTL	__ACCESS_CP15(c14, 0, c3, 1)
 #define CNTHCTL		__ACCESS_CP15(c14, 4, c1, 0)
 
-#define VFP_FPEXC	__ACCESS_VFP(FPEXC)
-
 /* AArch64 compatibility macros, only for the timer so far */
 #define read_sysreg_el0(r)		read_sysreg(r##_EL0)
 #define write_sysreg_el0(v, r)		write_sysreg(v, r##_EL0)

diff --git a/arch/arm/include/asm/vfp.h b/arch/arm/include/asm/vfp.h
@@ -9,13 +9,15 @@
 #ifndef __ASM_VFP_H
 #define __ASM_VFP_H
 
+#ifndef CONFIG_AS_VFP_VMRS_FPINST
 #define FPSID			cr0
 #define FPSCR			cr1
 #define MVFR1			cr6
 #define MVFR0			cr7
 #define FPEXC			cr8
 #define FPINST			cr9
 #define FPINST2			cr10
+#endif
 
 /* FPSID bits */
 #define FPSID_IMPLEMENTER_BIT	(24)

diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
@@ -8,14 +8,24 @@
 
 #include <asm/vfp.h>
 
-@ Macros to allow building with old toolkits (with no VFP support)
+#ifdef CONFIG_AS_VFP_VMRS_FPINST
+	.macro	VFPFMRX, rd, sysreg, cond
+	vmrs\cond	\rd, \sysreg
+	.endm
+
+	.macro	VFPFMXR, sysreg, rd, cond
+	vmsr\cond	\sysreg, \rd
+	.endm
+#else
+	@ Macros to allow building with old toolkits (with no VFP support)
 	.macro	VFPFMRX, rd, sysreg, cond
 	MRC\cond	p10, 7, \rd, \sysreg, cr0, 0	@ FMRX	\rd, \sysreg
 	.endm
 
 	.macro	VFPFMXR, sysreg, rd, cond
 	MCR\cond	p10, 7, \rd, \sysreg, cr0, 0	@ FMXR	\sysreg, \rd
 	.endm
+#endif
 
 	@ read all the working registers back into the VFP
 	.macro	VFPFLDMIA, base, tmp

diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
@@ -3,7 +3,7 @@
 # Makefile for Kernel-based Virtual Machine module
 #
 
-plus_virt := $(call as-instr,.arch_extension virt,+virt)
+plus_virt := $(call as-instr,".cpu cortex-a7\n\n.arch_extension virt",+virt)
 ifeq ($(plus_virt),+virt)
 	plus_virt_def := -DREQUIRES_VIRT=1
 endif

diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
@@ -8,6 +8,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
+#include "../../vfp/vfpinstr.h"
 
 __asm__(".arch_extension     virt");
 
@@ -26,10 +27,10 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu, u32 *fpexc_host)
 	 * trap to SVC.  Therefore, always make sure that for 32-bit guests,
 	 * we set FPEXC.EN to prevent traps to SVC, when setting the TCP bits.
 	 */
-	val = read_sysreg(VFP_FPEXC);
+	val = fmrx(FPEXC);
 	*fpexc_host = val;
 	if (!(val & FPEXC_EN)) {
-		write_sysreg(val | FPEXC_EN, VFP_FPEXC);
+		fmxr(FPEXC, val | FPEXC_EN);
 		isb();
 	}
 
@@ -196,7 +197,7 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 		__vfp_restore_state(&host_ctxt->vfp);
 	}
 
-	write_sysreg(fpexc, VFP_FPEXC);
+	fmxr(FPEXC, fpexc);
 
 	return exit_code;
 }

diff --git a/arch/arm/kvm/hyp/vfp.S b/arch/arm/kvm/hyp/vfp.S
@@ -8,6 +8,7 @@
 #include <asm/vfpmacros.h>
 
 	.text
+	.fpu vfpv2
 	.pushsection	.hyp.text, "ax"
 
 /* void __vfp_save_state(struct vfp_hard_struct *vfp); */

diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
@@ -35,6 +35,7 @@
  */
 
 	.text
+	.arch_extension virt
 	.pushsection    .hyp.idmap.text,"ax"
 	.align 5
 __kvm_hyp_init:

diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
@@ -7,6 +7,7 @@
 #include <linux/linkage.h>
 
 	.text
+	.arch_extension virt
 
 /********************************************************************
  *  Call function in Hyp mode

diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
@@ -78,6 +78,7 @@
 ENTRY(vfp_support_entry)
 	DBGSTR3	"instr %08x pc %08x state %p", r0, r2, r10
 
+	.fpu	vfpv2
 	VFPFMRX	r1, FPEXC		@ Is the VFP enabled?
 	DBGSTR1	"fpexc %08x", r1
 	tst	r1, #FPEXC_EN

diff --git a/arch/arm/vfp/vfpinstr.h b/arch/arm/vfp/vfpinstr.h
@@ -62,10 +62,23 @@
 #define FPSCR_C (1 << 29)
 #define FPSCR_V	(1 << 28)
 
-/*
- * Since we aren't building with -mfpu=vfp, we need to code
- * these instructions using their MRC/MCR equivalents.
- */
+#ifdef CONFIG_AS_VFP_VMRS_FPINST
+
+#define fmrx(_vfp_) ({			\
+	u32 __v;			\
+	asm(".fpu	vfpv2\n"	\
+	    "vmrs	%0, " #_vfp_	\
+	    : "=r" (__v) : : "cc");	\
+	__v;				\
+ })
+
+#define fmxr(_vfp_,_var_)		\
+	asm(".fpu	vfpv2\n"	\
+	    "vmsr	" #_vfp_ ", %0"	\
+	   : : "r" (_var_) : "cc")
+
+#else
+
 #define vfpreg(_vfp_) #_vfp_
 
 #define fmrx(_vfp_) ({			\
@@ -79,6 +92,8 @@
 	asm("mcr p10, 7, %0, " vfpreg(_vfp_) ", cr0, 0 @ fmxr	" #_vfp_ ", %0"	\
 	   : : "r" (_var_) : "cc")
 
+#endif
+
 u32 vfp_single_cpdo(u32 inst, u32 fpscr);
 u32 vfp_single_cprt(u32 inst, u32 fpscr, struct pt_regs *regs);