On Wed Mar 20, 2024 at 11:50 AM AEST, Benjamin Gray wrote:
> The GDB server protocol assigns an arbitrary numbering of the SPRs.
> We track this correspondence on each SPR with gdb_id, using it to
> resolve any SPR requests GDB makes.
>
> Early on we generate an XML representation of the SPRs to give GDB,
> including this numbering. However the XML is cached globally, and we
> skip setting the SPR gdb_id values on subsequent threads if we detect
> it is cached. This causes QEMU to fail to resolve SPR requests against
> secondary CPUs because it cannot find the matching gdb_id value on that
> thread's SPRs.
>
> This is a minimal fix to first assign the gdb_id values, then return
> early if the XML is cached. Otherwise we generate the XML using the
> now already initialised gdb_id values.
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
>
> Fixes: 1b53948ff8f7 ("target/ppc: Use GDBFeature for dynamic XML")
> Signed-off-by: Benjamin Gray <bg...@linux.ibm.com>
> ---
> target/ppc/gdbstub.c | 31 ++++++++++++++++++++-----------
> 1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/target/ppc/gdbstub.c b/target/ppc/gdbstub.c
> index 3f1e61bdb7..3b28d4e21c 100644
> --- a/target/ppc/gdbstub.c
> +++ b/target/ppc/gdbstub.c
> @@ -305,14 +305,6 @@ static void gdb_gen_spr_feature(CPUState *cs)
> unsigned int num_regs = 0;
> int i;
>
> - if (pcc->gdb_spr.xml) {
> - return;
> - }
> -
> - gdb_feature_builder_init(&builder, &pcc->gdb_spr,
> - "org.qemu.power.spr", "power-spr.xml",
> - cs->gdb_num_regs);
> -
> for (i = 0; i < ARRAY_SIZE(env->spr_cb); i++) {
> ppc_spr_t *spr = &env->spr_cb[i];
>
> @@ -320,9 +312,6 @@ static void gdb_gen_spr_feature(CPUState *cs)
> continue;
> }
>
> - gdb_feature_builder_append_reg(&builder, g_ascii_strdown(spr->name,
> -1),
> - TARGET_LONG_BITS, num_regs,
> - "int", "spr");
> /*
> * GDB identifies registers based on the order they are
> * presented in the XML. These ids will not match QEMU's
> @@ -335,6 +324,26 @@ static void gdb_gen_spr_feature(CPUState *cs)
> num_regs++;
> }
>
> + if (pcc->gdb_spr.xml) {
> + return;
> + }
> +
> + gdb_feature_builder_init(&builder, &pcc->gdb_spr,
> + "org.qemu.power.spr", "power-spr.xml",
> + cs->gdb_num_regs);
> +
> + for (i = 0; i < ARRAY_SIZE(env->spr_cb); i++) {
> + ppc_spr_t *spr = &env->spr_cb[i];
> +
> + if (!spr->name) {
> + continue;
> + }
> +
> + gdb_feature_builder_append_reg(&builder, g_ascii_strdown(spr->name,
> -1),
> + TARGET_LONG_BITS, spr->gdb_id,
> + "int", "spr");
> + }
> +
> gdb_feature_builder_end(&builder);
> }
> #endif
