From: Greg Kurz <groug@kaod.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: "Cédric Le Goater" <clg@kaod.org>,
qemu-ppc@nongnu.org, qemu-devel@nongnu.org,
"David Gibson" <david@gibson.dropbear.id.au>
Subject: Re: [Qemu-devel] [PATCH v6 3/4] spapr: Implement H_CONFER
Date: Thu, 18 Jul 2019 12:47:45 +0200 [thread overview]
Message-ID: <20190718124745.2f810234@bahia.lab.toulouse-stg.fr.ibm.com> (raw)
In-Reply-To: <20190718034214.14948-4-npiggin@gmail.com>
On Thu, 18 Jul 2019 13:42:13 +1000
Nicholas Piggin <npiggin@gmail.com> wrote:
> This does not do directed yielding and is not quite as strict as PAPR
> specifies in terms of precise dispatch behaviour. This generally will
> mean suboptimal performance, rather than guest misbehaviour. Linux
> does not rely on exact dispatch behaviour.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
Reviewed-by: Greg Kurz <groug@kaod.org>
> Changes since v5:
> - Cleanups
>
> Changes since v4:
> - Style, added justification comments, spelling.
> - Fixed trying to dereference spapr_cpu for a -1 target.
>
> hw/ppc/spapr_hcall.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 67 insertions(+)
>
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 098b3dda22..7c659dc75c 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1069,6 +1069,72 @@ static target_ulong h_cede(PowerPCCPU *cpu, SpaprMachineState *spapr,
> return H_SUCCESS;
> }
>
> +static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr,
> + target_ulong opcode, target_ulong *args)
> +{
> + target_long target = args[0];
> + uint32_t dispatch = args[1];
> + CPUState *cs = CPU(cpu);
> + SpaprCpuState *spapr_cpu;
> +
> + /*
> + * -1 means confer to all other CPUs without dispatch counter check,
> + * otherwise it's a targeted confer.
> + */
> + if (target != -1) {
> + PowerPCCPU *target_cpu = spapr_find_cpu(target);
> + uint32_t target_dispatch;
> +
> + if (!target_cpu) {
> + return H_PARAMETER;
> + }
> +
> + spapr_cpu = spapr_cpu_state(target_cpu);
> +
> + /*
> + * target == self is a special case, we wait until prodded, without
> + * dispatch counter check.
> + */
> + if (cpu == target_cpu) {
> + if (spapr_cpu->prod) {
> + spapr_cpu->prod = false;
> +
> + return H_SUCCESS;
> + }
> +
> + cs->halted = 1;
> + cs->exception_index = EXCP_HALTED;
> + cs->exit_request = 1;
> +
> + return H_SUCCESS;
> + }
> +
> + if (!spapr_cpu->vpa_addr || ((dispatch & 1) == 0)) {
> + return H_SUCCESS;
> + }
> +
> + target_dispatch = ldl_be_phys(cs->as,
> + spapr_cpu->vpa_addr + VPA_DISPATCH_COUNTER);
> + if (target_dispatch != dispatch) {
> + return H_SUCCESS;
> + }
> +
> + /*
> + * The targeted confer does not do anything special beyond yielding
> + * the current vCPU, but even this should be better than nothing.
> + * At least for single-threaded tcg, it gives the target a chance to
> + * run before we run again. Multi-threaded tcg does not really do
> + * anything with EXCP_YIELD yet.
> + */
> + }
> +
> + cs->exception_index = EXCP_YIELD;
> + cs->exit_request = 1;
> + cpu_loop_exit(cs);
> +
> + return H_SUCCESS;
> +}
> +
> static target_ulong h_prod(PowerPCCPU *cpu, SpaprMachineState *spapr,
> target_ulong opcode, target_ulong *args)
> {
> @@ -1912,6 +1978,7 @@ static void hypercall_register_types(void)
> /* hcall-splpar */
> spapr_register_hypercall(H_REGISTER_VPA, h_register_vpa);
> spapr_register_hypercall(H_CEDE, h_cede);
> + spapr_register_hypercall(H_CONFER, h_confer);
> spapr_register_hypercall(H_PROD, h_prod);
>
> spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);
next prev parent reply other threads:[~2019-07-18 10:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 3:42 [Qemu-devel] [PATCH v6 0/4] spapr: implement dispatch and suspend calls Nicholas Piggin
2019-07-18 3:42 ` [Qemu-devel] [PATCH v6 1/4] spapr: Implement dispatch tracking for tcg Nicholas Piggin
2019-07-18 10:13 ` Greg Kurz
2019-07-18 23:12 ` Nicholas Piggin
2019-07-19 2:27 ` David Gibson
2019-07-18 3:42 ` [Qemu-devel] [PATCH v6 2/4] spapr: Implement H_PROD Nicholas Piggin
2019-07-18 10:47 ` Greg Kurz
2019-07-18 3:42 ` [Qemu-devel] [PATCH v6 3/4] spapr: Implement H_CONFER Nicholas Piggin
2019-07-18 10:47 ` Greg Kurz [this message]
2019-07-18 3:42 ` [Qemu-devel] [PATCH v6 4/4] spapr: Implement H_JOIN Nicholas Piggin
2019-07-18 10:48 ` Greg Kurz
2019-07-18 4:31 ` [Qemu-devel] [PATCH v6 0/4] spapr: implement dispatch and suspend calls David Gibson
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