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.
Alex
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