[patch] x86: fix ESP corruption CPU bug

[Stas Sergeev]

Hello.

Brian Gerst wrote:
>> Can you tell me how the invisible high-word (invisible in VM-86, and
>> in real mode) could possibly harm something running in VM-86 or
>> read-mode ???  I don't even think it's a BUG. If the transition
>> into and out of VM-86 doesn't handle the fact that the high-word
>> of the stack hasn't been used in VM-86, then that piece of code
>> is bad (the SP isn't even the same stack, BTW).
> Because even in 16-bit mode (real, vm86 or 16-bit protected) you can use 
> 32-bit instructions, with an operand and/or address size override 
> prefix.
And the real problem is when the pure
32bit code is starting to use the 16bit
stack for some strange reasons. Looks like
the common technique for the early dos4gw
-based apps...