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Subject[PATCH v2 0/2] riscv: Correct the initialized flow of FP and __fstate_clean()
Date
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

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