On Tue, Oct 08, 2013 at 04:25:31PM +0200, Alexander Graf wrote:
>
> On 08.10.2013, at 16:12, Cédric Le Goater <clg@xxxxxxxxxx> wrote:
>
> > MMIO emulation reads the last instruction executed by the guest
> > and then emulates. If the guest is running in Little Endian mode,
> > the instruction needs to be byte-swapped before being emulated.
> >
> > This patch stores the last instruction in the endian order of the
> > host, primarily doing a byte-swap if needed. The common code
> > which fetches 'last_inst' uses a helper routine kvmppc_need_byteswap().
> > and the exit paths for the Book3S PV and HR guests use their own
> > version in assembly.
> >
> > Finally, the meaning of the 'is_bigendian' argument of the
> > routines kvmppc_handle_load() of kvmppc_handle_store() is
> > slightly changed to represent an eventual reverse operation. This
> > is used in conjunction with kvmppc_is_bigendian() to determine if
> > the instruction being emulated should be byte-swapped.
> >
> > Signed-off-by: Cédric Le Goater <clg@xxxxxxxxxx>
> > ---
> >
> > Changes in v2:
> >
> > - replaced rldicl. by andi. to test the MSR_LE bit in the guest
> > exit paths. (Paul Mackerras)
> >
> > - moved the byte swapping logic to kvmppc_handle_load() and
> > kvmppc_handle_load() by changing the is_bigendian parameter
> > meaning. (Paul Mackerras)
> >
> > arch/powerpc/include/asm/kvm_book3s.h | 9 ++++++++-
> > arch/powerpc/include/asm/kvm_ppc.h | 10 +++++-----
> > arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 +++++++++++
> > arch/powerpc/kvm/book3s_segment.S | 10 ++++++++++
> > arch/powerpc/kvm/emulate.c | 1 -
> > arch/powerpc/kvm/powerpc.c | 16 ++++++++++++----
> > 6 files changed, 46 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
> > index 4ee6c66..f043e62 100644
> > --- a/arch/powerpc/include/asm/kvm_book3s.h
> > +++ b/arch/powerpc/include/asm/kvm_book3s.h
> > @@ -289,7 +289,14 @@ static inline int kvmppc_ld32(struct kvm_vcpu *vcpu, ulong *eaddr,
> > static inline int kvmppc_ld_inst(struct kvm_vcpu *vcpu, ulong *eaddr,
> > u32 *inst)
> > {
> > - return kvmppc_ld32(vcpu, eaddr, inst, false);
> > + int ret;
> > +
> > + ret = kvmppc_ld32(vcpu, eaddr, inst, false);
> > +
> > + if (kvmppc_need_byteswap(vcpu))
> > + *inst = swab32(*inst);
>
> This logic wants to live in kvmppc_ld32(), no? Every 32bit access is going to need a byteswap, regardless of whether it's an instruction or not.
True, until we get to POWER8 with its split little-endian support,
where instructions and data can have different endianness...
Paul.
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