Xen devel - Oct 2007 - Re: [PATCH, fixed] linux/x86: use sysenter/syscall for 32-bit apps on 64-bit Xen

>>However, in case (2) the i386 guest kernel unconditionally goes for
>>sysenter, and the hypervisor will accept this because CPUID has
advertised
>>SEP. *But* AMD CPUs do not support sysenter except in legacy mode! The
>>correct thing to do is to use syscall. The hypervisor 32-on-64 compat
code
>>would accept CALLBACKTYPE_syscall, but the Linux i386 code here
doesn''t
>>appear to make use of it. So I would imagine that the i386 kernel
running on
>>AMD hardware would cause all user processes to crash when they SYSENTER.
>
>I intentionally avoided adding syscall stuff to the 32-bit kernel, since
that isn''t
>there in the native kernel either (as it''s not really usable on
native). Therefore
>I''d suggest clearing SEP for pv32-on-64 guests in
emulate_forced_invalid_op()
... on AMD CPUs I meant to say.

Jan


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