Re: [Qemu-devel] [PATCH 2/2] target-ppc: fix xscmpodp and xscmpudp decoding

[Richard W.M. Jones]

On Sun, Sep 13, 2015 at 11:03:45PM +0200, Aurelien Jarno wrote:
> The xscmpodp and xscmpudp instructions only have the AX, BX bits in
> there encoding, the lowest bit (usually TX) is marked as an invalid
> bit. We therefore can't decode them with GEN_XX2FORM, which decodes
> the two lowest bit.
> 
> Introduce a new form GEN_XX2FORM, which decodes AX and BX and mark
> the lowest bit as invalid.
> 
> Cc: Tom Musta <address@hidden>
> Cc: Alexander Graf <address@hidden>
> Cc: address@hidden
> Signed-off-by: Aurelien Jarno <address@hidden>
> ---
>  target-ppc/translate.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 84c5cea..c0eed13 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -10670,6 +10670,13 @@ GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 1, opc3, 0, 
> PPC_NONE, fl2), \
>  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 2, opc3, 0, PPC_NONE, fl2), \
>  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 3, opc3, 0, PPC_NONE, fl2)
>  
> +#undef GEN_XX2IFORM
> +#define GEN_XX2IFORM(name, opc2, opc3, fl2)                           \
> +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 0, opc3, 1, PPC_NONE, fl2), \
> +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 1, opc3, 1, PPC_NONE, fl2), \
> +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 2, opc3, 1, PPC_NONE, fl2), \
> +GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 3, opc3, 1, PPC_NONE, fl2)
> +
>  #undef GEN_XX3_RC_FORM
>  #define GEN_XX3_RC_FORM(name, opc2, opc3, fl2)                          \
>  GEN_HANDLER2_E(name, #name, 0x3C, opc2 | 0x00, opc3 | 0x00, 0, PPC_NONE, 
> fl2), \
> @@ -10731,8 +10738,8 @@ GEN_XX3FORM(xsnmaddadp, 0x04, 0x14, PPC2_VSX),
>  GEN_XX3FORM(xsnmaddmdp, 0x04, 0x15, PPC2_VSX),
>  GEN_XX3FORM(xsnmsubadp, 0x04, 0x16, PPC2_VSX),
>  GEN_XX3FORM(xsnmsubmdp, 0x04, 0x17, PPC2_VSX),
> -GEN_XX2FORM(xscmpodp,  0x0C, 0x05, PPC2_VSX),
> -GEN_XX2FORM(xscmpudp,  0x0C, 0x04, PPC2_VSX),
> +GEN_XX2IFORM(xscmpodp,  0x0C, 0x05, PPC2_VSX),
> +GEN_XX2IFORM(xscmpudp,  0x0C, 0x04, PPC2_VSX),
>  GEN_XX3FORM(xsmaxdp, 0x00, 0x14, PPC2_VSX),
>  GEN_XX3FORM(xsmindp, 0x00, 0x15, PPC2_VSX),
>  GEN_XX2FORM(xscvdpsp, 0x12, 0x10, PPC2_VSX),

This particular patch fixed a number of crashes I was experiencing in
libm in Fedora 22 (ppc64), which I traced to the xscmpudp instruction
causing SIGILL.

So:

  Tested-by: Richard W.M. Jones <address@hidden>

Cole: I think we should add this small patch series to Fedora, even
though it's not upstream yet, since it required for running F22/ppc64
guests reliably (on non-ppc hosts).

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/