RE: [PATCH] x86/mce: Fix set_mce_nospec() to avoid #GP fault

[David Laight]

From: Linus Torvalds
> ...
> You could literally do something like
> 
>     /* Make it canonical in case we flipped the high bit */
>     addr = (long)(addr<<1)>>1;

Isn't it safer to use a mask and let the compiler decide if two
shifts are a good implementation?

	addr &= ~HIGH_MAGIC_BIT;

ISTR fixing a bug in gld where it had (foo << 16) >> 16 instead
of foo & 0xffff. Didn't work well on 64bit.

(I may need to recompile that old gcc/gld again.
Failed miserably last time I tried.)

	David

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