From 96f95a17c1cfe65a002e525114d96616e91a8f2d Mon Sep 17 00:00:00 2001 From: Laura Abbott Date: Mon, 9 Jul 2018 13:09:56 -0700 Subject: Revert "arm64: Use aarch64elf and aarch64elfb emulation mode variants" This reverts commit 38fc4248677552ce35efc09902fdcb06b61d7ef9. Distributions such as Fedora and Debian do not package the ELF linker scripts with their toolchains, resulting in kernel build failures such as: | CHK include/generated/compile.h | LD [M] arch/arm64/crypto/sha512-ce.o | aarch64-linux-gnu-ld: cannot open linker script file ldscripts/aarch64elf.xr: No such file or directory | make[1]: *** [scripts/Makefile.build:530: arch/arm64/crypto/sha512-ce.o] Error 1 | make: *** [Makefile:1029: arch/arm64/crypto] Error 2 Revert back to the linux targets for now, adding a comment to the Makefile so we don't accidentally break this in the future. Cc: Paul Kocialkowski Cc: Fixes: 38fc42486775 ("arm64: Use aarch64elf and aarch64elfb emulation mode variants") Tested-by: Kevin Hilman Signed-off-by: Laura Abbott Signed-off-by: Will Deacon --- arch/arm64/Makefile | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 7976d2d242fa..e7101b19d590 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -60,13 +60,15 @@ ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__ AS += -EB -LDFLAGS += -EB -maarch64elfb +# We must use the linux target here, since distributions don't tend to package +# the ELF linker scripts with binutils, and this results in a build failure. +LDFLAGS += -EB -maarch64linuxb UTS_MACHINE := aarch64_be else KBUILD_CPPFLAGS += -mlittle-endian CHECKFLAGS += -D__AARCH64EL__ AS += -EL -LDFLAGS += -EL -maarch64elf +LDFLAGS += -EL -maarch64linux # See comment above UTS_MACHINE := aarch64 endif -- cgit From 2fd8eb4ad87104c54800ef3cea498c92eb15c78a Mon Sep 17 00:00:00 2001 From: Yandong Zhao Date: Wed, 11 Jul 2018 19:06:28 +0800 Subject: arm64: neon: Fix function may_use_simd() return error status It does not matter if the caller of may_use_simd() migrates to another cpu after the call, but it is still important that the kernel_neon_busy percpu instance that is read matches the cpu the task is running on at the time of the read. This means that raw_cpu_read() is not sufficient. kernel_neon_busy may appear true if the caller migrates during the execution of raw_cpu_read() and the next task to be scheduled in on the initial cpu calls kernel_neon_begin(). This patch replaces raw_cpu_read() with this_cpu_read() to protect against this race. Cc: Fixes: cb84d11e1625 ("arm64: neon: Remove support for nested or hardirq kernel-mode NEON") Acked-by: Ard Biesheuvel Reviewed-by: Dave Martin Reviewed-by: Mark Rutland Signed-off-by: Yandong Zhao Signed-off-by: Will Deacon --- arch/arm64/include/asm/simd.h | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) (limited to 'arch') diff --git a/arch/arm64/include/asm/simd.h b/arch/arm64/include/asm/simd.h index fa8b3fe932e6..6495cc51246f 100644 --- a/arch/arm64/include/asm/simd.h +++ b/arch/arm64/include/asm/simd.h @@ -29,20 +29,15 @@ DECLARE_PER_CPU(bool, kernel_neon_busy); static __must_check inline bool may_use_simd(void) { /* - * The raw_cpu_read() is racy if called with preemption enabled. - * This is not a bug: kernel_neon_busy is only set when - * preemption is disabled, so we cannot migrate to another CPU - * while it is set, nor can we migrate to a CPU where it is set. - * So, if we find it clear on some CPU then we're guaranteed to - * find it clear on any CPU we could migrate to. - * - * If we are in between kernel_neon_begin()...kernel_neon_end(), - * the flag will be set, but preemption is also disabled, so we - * can't migrate to another CPU and spuriously see it become - * false. + * kernel_neon_busy is only set while preemption is disabled, + * and is clear whenever preemption is enabled. Since + * this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy + * cannot change under our feet -- if it's set we cannot be + * migrated, and if it's clear we cannot be migrated to a CPU + * where it is set. */ return !in_irq() && !irqs_disabled() && !in_nmi() && - !raw_cpu_read(kernel_neon_busy); + !this_cpu_read(kernel_neon_busy); } #else /* ! CONFIG_KERNEL_MODE_NEON */ -- cgit