Re: [Qemu-devel] [PATCH 15/35] tcg-s390: Query instruction extensions that are installed.

[Aurelien Jarno]

On Fri, Jun 11, 2010 at 06:07:52AM -0700, Richard Henderson wrote:
> On 06/11/2010 01:06 AM, Aurelien Jarno wrote:
> > What's the difference between FACILITY_ZARCH and FACILITY_ZARCH_ACTIVE,
> > as both are actually flagged together. My guess is that
> > FACILITY_ZARCH_ACTIVE is needed in 64-bit mode, why FACILITY_ZARCH is
> > only needed for a possible future 32-bit mode. Is it correct?
> 
> Loosely,
> 
> ZARCH is set when the system is 64-bit capable, whether or not it is active.
> The OS would check this bit at startup if it wanted to change modes.  This
> bit isn't really interesting to us in userspace.
> 
> ZARCH_ACTIVE is set when the system is in 64-bit mode, i.e. you've booted
> with a 64-bit kernel.  Note that this says nothing about the address 
> decoding mode -- this bit can be set while the PSW is set for 31-bit
> address translation, e.g. running a 32-bit program on a 64-bit kernel.
> 

So in short we never use ZARCH in QEMU, so we probably don't want to
have this #define, nor add it at the same time as FACILITY_ZARCH_ACTIVE.


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
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