Re: [PATCH] target/ppc: Fix lxv/stxv MSR facility check

[Fabiano Rosas <farosas@suse.de>]

Nicholas Piggin <npiggin@gmail.com> writes:

> The move to decodetree flipped the inequality test for the VEC / VSX
> MSR facility check.
>
> This caused application crashes under Linux, where these facility
> unavailable interrupts are used for lazy-switching of VEC/VSX register
> sets. Getting the incorrect interrupt would result in wrong registers
> being loaded, potentially overwriting live values and/or exposing
> stale ones.
>
> Cc: qemu-stable@nongnu.org
> Reported-by: Joel Stanley <joel@jms.id.au>
> Fixes: 70426b5bb738 ("target/ppc: moved stxvx and lxvx from legacy to decodtree")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1769
> Tested-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  target/ppc/translate/vsx-impl.c.inc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/ppc/translate/vsx-impl.c.inc b/target/ppc/translate/vsx-impl.c.inc
> index 6db87ab336..0266f09119 100644
> --- a/target/ppc/translate/vsx-impl.c.inc
> +++ b/target/ppc/translate/vsx-impl.c.inc
> @@ -2268,7 +2268,7 @@ static bool do_lstxv(DisasContext *ctx, int ra, TCGv displ,
>  
>  static bool do_lstxv_D(DisasContext *ctx, arg_D *a, bool store, bool paired)
>  {
> -    if (paired || a->rt >= 32) {
> +    if (paired || a->rt < 32) {
>          REQUIRE_VSX(ctx);
>      } else {
>          REQUIRE_VECTOR(ctx);

What about the X-form down below?

static bool do_lstxv_X(DisasContext *ctx, arg_X *a, bool store, bool paired)
{
    if (paired || a->rt >= 32) {
        REQUIRE_VSX(ctx);
    } else {
        REQUIRE_VECTOR(ctx);
    }

    return do_lstxv(ctx, a->ra, cpu_gpr[a->rb], a->rt, store, paired);
}