The following two reasons cause FP registers are sometimes not initialized before starting the user program. 1. Currently, the FP context is initialized in flush_thread() function and we expect these initial values to be restored to FP register when doing FP context switch. However, the FP context switch only occurs in switch_to function. Hence, if this process does not be scheduled out and scheduled in before entering the user space, the FP registers have no chance to initialize. 2. In flush_thread(), the state of reg->sstatus.FS inherits from the parent. Hence, the state of reg->sstatus.FS may be dirty. If this process is scheduled out during flush_thread() and initializing the FP register, the fstate_save() in switch_to will corrupt the FP context which has been initialized until flush_thread(). In addition, the __fstate_clean() function cannot correctly set the state of sstatus.FS to SR_FS_CLEAN. These problems will be solved in this patch set.
Changes since v1: - Remove unneeded braces - Remove unneeded ifdef condition - Make the correction for __fstate_clean() be a RC fix Vincent Chen (2): riscv: Correct the initialized flow of FP register riscv: Make __fstate_clean() work correctly. arch/riscv/include/asm/switch_to.h | 8 +++++++- arch/riscv/kernel/process.c | 11 +++++++++-- 2 files changed, 16 insertions(+), 3 deletions(-) -- 2.7.4
