aae538cd03
It is not sufficient to check if a toolchain supports a particular
extension without checking if the linker supports that extension
too. For example, Clang 15 supports Zihintpause but GNU bintutils
2.35.2 does not, leading build errors like so:
riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zihintpause'
Add a TOOLCHAIN_HAS_ZIHINTPAUSE which checks if each of the compiler,
assembler and linker support the extension. Replace the ifdef in the
vdso with one depending on this new symbol.
Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20221006173520.1785507-3-conor@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
37 lines
843 B
C
37 lines
843 B
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __ASM_VDSO_PROCESSOR_H
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#define __ASM_VDSO_PROCESSOR_H
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#ifndef __ASSEMBLY__
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#include <linux/jump_label.h>
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#include <asm/barrier.h>
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#include <asm/hwcap.h>
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static inline void cpu_relax(void)
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{
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if (!static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_ZIHINTPAUSE])) {
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#ifdef __riscv_muldiv
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int dummy;
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/* In lieu of a halt instruction, induce a long-latency stall. */
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__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
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#endif
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} else {
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/*
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* Reduce instruction retirement.
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* This assumes the PC changes.
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*/
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#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
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__asm__ __volatile__ ("pause");
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#else
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/* Encoding of the pause instruction */
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__asm__ __volatile__ (".4byte 0x100000F");
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#endif
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}
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barrier();
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}
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_VDSO_PROCESSOR_H */
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