On Fri, Mar 18, 2016 at 09:28:33AM +0100, Thomas Huth wrote:
> On 16.03.2016 16:13, Laurent Vivier wrote:
> > Check in MSR if the SF bit is set (64bit mode is enabled)
> >
> > Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
> > ---
> > powerpc/emulator.c | 14 ++++++++++++++f958ee745f70
> > 1 file changed, 14 insertions(+)
> >
> > diff --git a/powerpc/emulator.c b/powerpc/emulator.c
> > index 1215c4f..b66c1d7 100644
> > --- a/powerpc/emulator.c
> > +++ b/powerpc/emulator.c
> > @@ -32,12 +32,26 @@ static void test_illegal(void)
> > report_prefix_pop();
> > }
> >
> > +static void test_64bit(void)
> > +{
> > + uint64_t msr;
> > +
> > + report_prefix_push("64bit");
> > +
> > + asm("mfmsr %[msr]": [msr] "=r" (msr));
> > +
> > + report("detected", msr & 0x8000000000000000UL);
> > +
> > + report_prefix_pop();
> > +}
> > +
> > int main(void)
> > {
> > handle_exception(0x700, program_check_handler, (void *)&is_invalid);
> >
> > report_prefix_push("emulator");
> >
> > + test_64bit();
> > test_illegal();
> >
> > report_prefix_pop();
>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
>
> But I still wonder how kvm-unit-tests worked at all before the 64-bit
> mode has been fixed in QEMU ... I mean kvm-unit-tests is compiled with
> 64-bit code, but it's still working when run in 32-bit? Something really
> strange was going on here...
On Power processors, there's not as much difference between 32-bit and
64-bit mode as you might expect. In 32-bit mode on a 64-bit
processor, you can use all 64 bits of the registers and execute 64-bit
instructions. The only things that change in 32-bit mode are that (a)
effective addresses are truncated to 32 bits and (b) dot-form
instructions (e.g. "add.") set CR0 based on the 32-bit result rather
than the 64-bit result.
Paul.
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