From: Greg Kurz <groug@kaod.org> To: "Philippe Mathieu-Daudé" <philmd@redhat.com> Cc: qemu-devel@nongnu.org, Peter Maydell <peter.maydell@linaro.org>, Eduardo Habkost <ehabkost@redhat.com>, kvm@vger.kernel.org, Juan Quintela <quintela@redhat.com>, qemu-ppc@nongnu.org, Marcelo Tosatti <mtosatti@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, qemu-arm@nongnu.org, Alistair Francis <alistair.francis@wdc.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, David Gibson <david@gibson.dropbear.id.au>, Richard Henderson <rth@twiddle.net>, Eric Blake <eblake@redhat.com> Subject: Re: [PATCH 04/15] hw/ppc/spapr_rtas: Restrict variables scope to single switch case Date: Fri, 10 Jan 2020 10:50:55 +0100 [thread overview] Message-ID: <20200110105055.3e72ddf4@bahia.lan> (raw) In-Reply-To: <9870f8ed-3fa0-1deb-860d-7481cb3db556@redhat.com> On Fri, 10 Jan 2020 10:34:07 +0100 Philippe Mathieu-Daudé <philmd@redhat.com> wrote: > On 1/9/20 6:43 PM, Greg Kurz wrote: > > On Thu, 9 Jan 2020 16:21:22 +0100 > > Philippe Mathieu-Daudé <philmd@redhat.com> wrote: > > > >> We only access these variables in RTAS_SYSPARM_SPLPAR_CHARACTERISTICS > >> case, restrict their scope to avoid unnecessary initialization. > >> > > > > I guess a decent compiler can be smart enough detect that the initialization > > isn't needed outside of the RTAS_SYSPARM_SPLPAR_CHARACTERISTICS branch... > > Anyway, reducing scope isn't bad. The only hitch I could see is that some > > people do prefer to have all variables declared upfront, but there's a nested > > param_val variable already so I guess it's okay. > > I don't want to outsmart compilers :) > > The MACHINE() macro is not a simple cast, it does object introspection > with OBJECT_CHECK(), thus is not free. Since Sure, I understand the motivation in avoiding an unneeded call to calling object_dynamic_cast_assert(). > object_dynamic_cast_assert() argument is not const, I'm not sure the > compiler can remove the call. > Not remove the call, but delay it to the branch that uses it, ie. parameter == RTAS_SYSPARM_SPLPAR_CHARACTERISTICS. > Richard, Eric, do you know? > > >> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> > >> --- > >> hw/ppc/spapr_rtas.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c > >> index 6f06e9d7fe..7237e5ebf2 100644 > >> --- a/hw/ppc/spapr_rtas.c > >> +++ b/hw/ppc/spapr_rtas.c > >> @@ -267,8 +267,6 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu, > >> uint32_t nret, target_ulong rets) > >> { > >> PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); > >> - MachineState *ms = MACHINE(spapr); > >> - unsigned int max_cpus = ms->smp.max_cpus; > >> target_ulong parameter = rtas_ld(args, 0); > >> target_ulong buffer = rtas_ld(args, 1); > >> target_ulong length = rtas_ld(args, 2); > >> @@ -276,6 +274,8 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu, > >> > >> switch (parameter) { > >> case RTAS_SYSPARM_SPLPAR_CHARACTERISTICS: { > >> + MachineState *ms = MACHINE(spapr); > >> + unsigned int max_cpus = ms->smp.max_cpus; > > > > The max_cpus variable used to be a global. Now that it got moved > > below ms->smp, I'm not sure it's worth keeping it IMHO. What about > > dropping it completely and do: > > > > char *param_val = g_strdup_printf("MaxEntCap=%d," > > "DesMem=%" PRIu64 "," > > "DesProcs=%d," > > "MaxPlatProcs=%d", > > ms->smp.max_cpus, > > current_machine->ram_size / MiB, > > ms->smp.cpus, > > ms->smp.max_cpus); > > OK, good idea. > > > And maybe insert an empty line between the declaration of param_val > > and the code for a better readability ? > > > >> char *param_val = g_strdup_printf("MaxEntCap=%d," > >> "DesMem=%" PRIu64 "," > >> "DesProcs=%d," > > >
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kurz <groug@kaod.org> To: "Philippe Mathieu-Daudé" <philmd@redhat.com> Cc: Peter Maydell <peter.maydell@linaro.org>, Eduardo Habkost <ehabkost@redhat.com>, kvm@vger.kernel.org, Juan Quintela <quintela@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, qemu-arm@nongnu.org, qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Alistair Francis <alistair.francis@wdc.com>, Richard Henderson <rth@twiddle.net>, David Gibson <david@gibson.dropbear.id.au> Subject: Re: [PATCH 04/15] hw/ppc/spapr_rtas: Restrict variables scope to single switch case Date: Fri, 10 Jan 2020 10:50:55 +0100 [thread overview] Message-ID: <20200110105055.3e72ddf4@bahia.lan> (raw) In-Reply-To: <9870f8ed-3fa0-1deb-860d-7481cb3db556@redhat.com> On Fri, 10 Jan 2020 10:34:07 +0100 Philippe Mathieu-Daudé <philmd@redhat.com> wrote: > On 1/9/20 6:43 PM, Greg Kurz wrote: > > On Thu, 9 Jan 2020 16:21:22 +0100 > > Philippe Mathieu-Daudé <philmd@redhat.com> wrote: > > > >> We only access these variables in RTAS_SYSPARM_SPLPAR_CHARACTERISTICS > >> case, restrict their scope to avoid unnecessary initialization. > >> > > > > I guess a decent compiler can be smart enough detect that the initialization > > isn't needed outside of the RTAS_SYSPARM_SPLPAR_CHARACTERISTICS branch... > > Anyway, reducing scope isn't bad. The only hitch I could see is that some > > people do prefer to have all variables declared upfront, but there's a nested > > param_val variable already so I guess it's okay. > > I don't want to outsmart compilers :) > > The MACHINE() macro is not a simple cast, it does object introspection > with OBJECT_CHECK(), thus is not free. Since Sure, I understand the motivation in avoiding an unneeded call to calling object_dynamic_cast_assert(). > object_dynamic_cast_assert() argument is not const, I'm not sure the > compiler can remove the call. > Not remove the call, but delay it to the branch that uses it, ie. parameter == RTAS_SYSPARM_SPLPAR_CHARACTERISTICS. > Richard, Eric, do you know? > > >> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> > >> --- > >> hw/ppc/spapr_rtas.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c > >> index 6f06e9d7fe..7237e5ebf2 100644 > >> --- a/hw/ppc/spapr_rtas.c > >> +++ b/hw/ppc/spapr_rtas.c > >> @@ -267,8 +267,6 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu, > >> uint32_t nret, target_ulong rets) > >> { > >> PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); > >> - MachineState *ms = MACHINE(spapr); > >> - unsigned int max_cpus = ms->smp.max_cpus; > >> target_ulong parameter = rtas_ld(args, 0); > >> target_ulong buffer = rtas_ld(args, 1); > >> target_ulong length = rtas_ld(args, 2); > >> @@ -276,6 +274,8 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu, > >> > >> switch (parameter) { > >> case RTAS_SYSPARM_SPLPAR_CHARACTERISTICS: { > >> + MachineState *ms = MACHINE(spapr); > >> + unsigned int max_cpus = ms->smp.max_cpus; > > > > The max_cpus variable used to be a global. Now that it got moved > > below ms->smp, I'm not sure it's worth keeping it IMHO. What about > > dropping it completely and do: > > > > char *param_val = g_strdup_printf("MaxEntCap=%d," > > "DesMem=%" PRIu64 "," > > "DesProcs=%d," > > "MaxPlatProcs=%d", > > ms->smp.max_cpus, > > current_machine->ram_size / MiB, > > ms->smp.cpus, > > ms->smp.max_cpus); > > OK, good idea. > > > And maybe insert an empty line between the declaration of param_val > > and the code for a better readability ? > > > >> char *param_val = g_strdup_printf("MaxEntCap=%d," > >> "DesMem=%" PRIu64 "," > >> "DesProcs=%d," > > >
next prev parent reply other threads:[~2020-01-10 10:09 UTC|newest] Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-09 15:21 [PATCH 00/15] Replace current_machine by qdev_get_machine() Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-09 15:21 ` [PATCH 01/15] target/arm/kvm: Use CPUState::kvm_state in kvm_arm_pmu_supported() Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-10 9:59 ` Alistair Francis 2020-01-10 9:59 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 02/15] hw/ppc/spapr_rtas: Use local MachineState variable Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-09 17:13 ` Greg Kurz 2020-01-09 17:13 ` Greg Kurz 2020-01-13 1:11 ` David Gibson 2020-01-13 1:11 ` David Gibson 2020-01-09 15:21 ` [PATCH 03/15] hw/ppc/spapr_rtas: Access MachineState via SpaprMachineState argument Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-09 17:13 ` Greg Kurz 2020-01-09 17:13 ` Greg Kurz 2020-01-13 1:11 ` David Gibson 2020-01-13 1:11 ` David Gibson 2020-01-09 15:21 ` [PATCH 04/15] hw/ppc/spapr_rtas: Restrict variables scope to single switch case Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-09 17:43 ` Greg Kurz 2020-01-09 17:43 ` Greg Kurz 2020-01-10 9:34 ` Philippe Mathieu-Daudé 2020-01-10 9:34 ` Philippe Mathieu-Daudé 2020-01-10 9:50 ` Greg Kurz [this message] 2020-01-10 9:50 ` Greg Kurz 2020-01-10 19:18 ` Eric Blake 2020-01-10 19:18 ` Eric Blake 2020-01-13 7:16 ` David Gibson 2020-01-13 7:16 ` David Gibson 2020-01-09 15:21 ` [PATCH 05/15] device-hotplug: Replace current_machine by qdev_get_machine() Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-12 9:42 ` Alistair Francis 2020-01-12 9:42 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 06/15] migration/savevm: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-09 15:52 ` Dr. David Alan Gilbert 2020-01-09 15:52 ` Dr. David Alan Gilbert 2020-01-12 9:43 ` Alistair Francis 2020-01-12 9:43 ` Alistair Francis 2020-01-14 13:27 ` Juan Quintela 2020-01-14 13:27 ` Juan Quintela 2020-01-09 15:21 ` [PATCH 07/15] hw/core/machine-qmp-cmds: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-12 9:44 ` Alistair Francis 2020-01-12 9:44 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 08/15] target/arm/monitor: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-12 9:47 ` Alistair Francis 2020-01-12 9:47 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 09/15] device_tree: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-12 9:47 ` Alistair Francis 2020-01-12 9:47 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 10/15] memory: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-12 9:48 ` Alistair Francis 2020-01-12 9:48 ` Alistair Francis 2020-01-12 13:45 ` Philippe Mathieu-Daudé 2020-01-12 13:45 ` Philippe Mathieu-Daudé 2020-01-14 2:02 ` Alistair Francis 2020-01-14 2:02 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 11/15] exec: " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-14 1:57 ` Alistair Francis 2020-01-14 1:57 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 12/15] accel: Introduce the current_accel() method Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-14 1:59 ` Alistair Francis 2020-01-14 1:59 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 13/15] accel: Replace current_machine->accelerator by " Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-14 1:58 ` Alistair Francis 2020-01-14 1:58 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 14/15] accel/accel: Replace current_machine by qdev_get_machine() Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-14 1:59 ` Alistair Francis 2020-01-14 1:59 ` Alistair Francis 2020-01-09 15:21 ` [PATCH 15/15] vl: Make current_machine a local variable Philippe Mathieu-Daudé 2020-01-09 15:21 ` Philippe Mathieu-Daudé 2020-01-14 2:00 ` Alistair Francis 2020-01-14 2:00 ` Alistair Francis 2020-01-21 8:59 ` [PATCH 00/15] Replace current_machine by qdev_get_machine() Markus Armbruster 2020-01-21 8:59 ` Markus Armbruster
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