Re: [PATCH 5.4 55/86] x86/mmx: Use KFPU_387 for MMX string operations

2021-01-26 Thread Krzysztof Olędzki
On 2021-01-25 at 10:39, Greg Kroah-Hartman wrote: From: Andy Lutomirski commit 67de8dca50c027ca0fa3b62a488ee5035036a0da upstream. The default kernel_fpu_begin() doesn't work on systems that support XMM but haven't yet enabled CR4.OSFXSR. This causes crashes when _mmx_memcpy() is called too

[PATCH 5.4 55/86] x86/mmx: Use KFPU_387 for MMX string operations

2021-01-25 Thread Greg Kroah-Hartman
From: Andy Lutomirski commit 67de8dca50c027ca0fa3b62a488ee5035036a0da upstream. The default kernel_fpu_begin() doesn't work on systems that support XMM but haven't yet enabled CR4.OSFXSR. This causes crashes when _mmx_memcpy() is called too early because LDMXCSR generates #UD when the