[5.10] [bugfix] : Resolve FPU state corruption between atomic and non-atomic contexts · Pull Request !6329 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=29391

This patch fixes a critical race condition introduced by commit
    ("anolis: arch/x86/lib: Enhanced Hygon processor's processing capabilities") 
where FPU state corruption occurs when:

1. A non-atomic NT copy operation (using kernel_fpu_begin_nonatomic) is
   in progress for large memory copies
2. An atomic context (e.g., network softirq handling IPsec crypto)
   enters and calls kernel_fpu_begin()
3. The FPU register state becomes corrupted because both contexts try to
   manage the same FPU registers without proper isolation

The corruption manifests as:
- Random data corruption in copied memory regions
- Crypto operation failures with invalid ciphertext
- Occasional kernel panics in fpstate management code

Root cause analysis revealed that the original implementation:
- Used a single in_kernel_fpu flag for atomic contexts
- Did not properly save/restore non-atomic FPU state during atomic preemption
- Allowed atomic contexts to overwrite non-atomic FPU registers

类型	指派人员	状态
审查	xunlei 半叶枫尘 Artie Ding 冯光辉 Guixin Liu kun-llfl Xuchun Shang Xiaochen Shen yehuaisheng hygon-anolis-reviewers	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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