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

[Aurelien Jarno <aurelien@aurel32.net>]

On Sun, Jun 13, 2010 at 09:02:40AM -0700, Richard Henderson wrote:
> On 06/13/2010 03:49 AM, Aurelien Jarno wrote:
> >> Also, what era is that second machine without highgprs?  Is it running an
> >> old kernel, or a 32-bit kernel?
> > 
> > I have very few infos about it, it's an IBM System z10 machine running a
> > 64-bit 2.6.26 kernel.
> 
> Ah, I see it now: ea2a4d3a3a929ef494952bba57a0ef1a8a877881
> 
>     [S390] 64-bit register support for 31-bit processes
> 
> which adds a mechanism to pass the high parts of the gprs
> in the ucontext to the 31-bit signal handler, and adds a
> spot for them in the 31-bit core dump.
> 
> It doesn't change the actual saving of registers within
> the kernel.  Since we take asynchronous signals and return
> from them (as opposed to always longjmping out), we cannot
> use the full 64-bit register within a 31-bit process without
> having that bit set in HWCAP.
> 
> Something to remember if we ever implement TCG for 31-bit mode.
> At the moment we only allow KVM in 31-bit mode.
> 

Is KVM in 31-bit mode actually functional?

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net