Hosts the 0x221E linux distro kernel. https://universe.0xinfinity.dev/distro/kernel/atom?h=linux-5.1.y 2018-07-11T16:02:02Z 2018-07-11T16:02:02Z Yandong Zhao yandong77520@gmail.com 2018-07-11T11:06:28Z urn:sha1:2fd8eb4ad87104c54800ef3cea498c92eb15c78a 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: <stable@vger.kernel.org> Fixes: cb84d11e1625 ("arm64: neon: Remove support for nested or hardirq kernel-mode NEON") Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Yandong Zhao <yandong77520@gmail.com> Signed-off-by: Will Deacon <will.deacon@arm.com> 2017-08-09T14:05:59Z Dave Martin Dave.Martin@arm.com 2017-08-09T10:43:28Z urn:sha1:66c3ec5a712005625437474cf5a04148d7890350 Currently, may_use_simd() can return true if IRQs are disabled. If the caller goes ahead and calls kernel_neon_begin(), this can result in use of local_bh_enable() in an unsafe context. In particular, __efi_fpsimd_begin() may do this when calling EFI as part of system shutdown. This patch ensures that callers don't think they can use kernel_neon_begin() in such a context. Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 2017-08-04T14:00:57Z Dave Martin Dave.Martin@arm.com 2017-08-03T16:23:23Z urn:sha1:cb84d11e1625aa3a081d898ca2640bf3a9ca0e96 Support for kernel-mode NEON to be nested and/or used in hardirq context adds significant complexity, and the benefits may be marginal. In practice, kernel-mode NEON is not used in hardirq context, and is rarely used in softirq context (by certain mac80211 drivers). This patch implements an arm64 may_use_simd() function to allow clients to check whether kernel-mode NEON is usable in the current context, and simplifies kernel_neon_{begin,end}() to handle only saving of the task FPSIMD state (if any). Without nesting, there is no other state to save. The partial fpsimd save/restore functions become redundant as a result of these changes, so they are removed too. The save/restore model is changed to operate directly on task_struct without additional percpu storage. This simplifies the code and saves a bit of memory, but means that softirqs must now be disabled when manipulating the task fpsimd state from task context: correspondingly, preempt_{en,dis}sable() calls are upgraded to local_bh_{en,dis}able() as appropriate. fpsimd_thread_switch() already runs with hardirqs disabled and so is already protected from softirqs. These changes should make it easier to support kernel-mode NEON in the presence of the Scalable Vector extension in the future. Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 2017-08-04T14:00:47Z Ard Biesheuvel ard.biesheuvel@linaro.org 2017-08-03T16:23:19Z urn:sha1:f960181d5d88ab6c84be8fb5e7f75080c78dfdd1 In preparation of modifying the logic that decides whether kernel mode NEON is allowable, which is required for SVE support, introduce an implementation of may_use_simd() that reflects the current reality, i.e., that SIMD is allowed in any context. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>