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* [PATCH v2 0/2] riscv: Correct the initialized flow of FP and __fstate_clean()
@ 2019-08-14  8:23 Vincent Chen
  2019-08-14  8:23 ` [PATCH v2 1/2] riscv: Correct the initialized flow of FP register Vincent Chen
  2019-08-14  8:23 ` [PATCH v2 2/2] riscv: Make __fstate_clean() work correctly Vincent Chen
  0 siblings, 2 replies; 11+ messages in thread
From: Vincent Chen @ 2019-08-14  8:23 UTC (permalink / raw)
  To: Paul Walmsley, Palmer Dabbelt; +Cc: Vincent Chen, linux-riscv, linux-kernel

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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^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, other threads:[~2019-09-11  7:31 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-14  8:23 [PATCH v2 0/2] riscv: Correct the initialized flow of FP and __fstate_clean() Vincent Chen
2019-08-14  8:23 ` [PATCH v2 1/2] riscv: Correct the initialized flow of FP register Vincent Chen
2019-08-14 20:24   ` Paul Walmsley
2019-08-14  8:23 ` [PATCH v2 2/2] riscv: Make __fstate_clean() work correctly Vincent Chen
2019-08-14 20:32   ` Paul Walmsley
2019-08-14 21:29     ` Palmer Dabbelt
2019-08-14 22:17       ` Andreas Schwab
2019-08-15  1:53         ` Palmer Dabbelt
2019-08-15  2:53         ` Vincent Chen
2019-09-11  7:22         ` Geert Uytterhoeven
2019-09-11  7:31           ` Andreas Schwab

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