From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41206) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eD8WK-0002AR-Uv for qemu-devel@nongnu.org; Fri, 10 Nov 2017 07:34:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eD8WG-0002MS-7q for qemu-devel@nongnu.org; Fri, 10 Nov 2017 07:34:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35652) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eD8WF-0002KD-V7 for qemu-devel@nongnu.org; Fri, 10 Nov 2017 07:34:48 -0500 References: <1508170976-96869-4-git-send-email-imammedo@redhat.com> <1508325132-70513-1-git-send-email-imammedo@redhat.com> <20171019063151.GA13245@umbus> <20171031150114.60e0958e@nial.brq.redhat.com> <20171106180216.GT3111@localhost.localdomain> <20171107160404.40e368da.cohuck@redhat.com> <20171109065803.GG7732@umbus.fritz.box> <20171109200235.GG3111@localhost.localdomain> <20171110111403.636682ea.cohuck@redhat.com> From: David Hildenbrand Message-ID: <7cda4233-2f8b-cfdc-3468-9416c9b5a855@redhat.com> Date: Fri, 10 Nov 2017 13:34:42 +0100 MIME-Version: 1.0 In-Reply-To: <20171110111403.636682ea.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC v2 3/6] possible_cpus: add CPUArchId::type field List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck , Eduardo Habkost Cc: David Gibson , Igor Mammedov , qemu-devel@nongnu.org, peter.maydell@linaro.org, pkrempa@redhat.com, pbonzini@redhat.com, drjones@redhat.com On 10.11.2017 11:14, Cornelia Huck wrote: > On Thu, 9 Nov 2017 18:02:35 -0200 > Eduardo Habkost wrote: > >> On Thu, Nov 09, 2017 at 05:58:03PM +1100, David Gibson wrote: >>> On Tue, Nov 07, 2017 at 04:04:04PM +0100, Cornelia Huck wrote: >>>> On Mon, 6 Nov 2017 16:02:16 -0200 >>>> Eduardo Habkost wrote: >>>> >>>>> On Tue, Oct 31, 2017 at 03:01:14PM +0100, Igor Mammedov wrote: >>>>>> On Thu, 19 Oct 2017 17:31:51 +1100 >>>>>> David Gibson wrote: >>>>>> >>>>>>> On Wed, Oct 18, 2017 at 01:12:12PM +0200, Igor Mammedov wrote: >>>>>>>> For enabling early cpu to numa node configuration at runtime >>>>>>>> qmp_query_hotpluggable_cpus() should provide a list of available >>>>>>>> cpu slots at early stage, before machine_init() is called and >>>>>>>> the 1st cpu is created, so that mgmt might be able to call it >>>>>>>> and use output to set numa mapping. >>>>>>>> Use MachineClass::possible_cpu_arch_ids() callback to set >>>>>>>> cpu type info, along with the rest of possible cpu properties, >>>>>>>> to let machine define which cpu type* will be used. >>>>>>>> >>>>>>>> * for SPAPR it will be a spapr core type and for ARM/s390x/x86 >>>>>>>> a respective descendant of CPUClass. >>>>>>>> >>>>>>>> Move parse_numa_opts() in vl.c after cpu_model is parsed into >>>>>>>> cpu_type so that possible_cpu_arch_ids() would know which >>>>>>>> cpu_type to use during layout initialization. >>>>>>>> >>>>>>>> Signed-off-by: Igor Mammedov >>>>>>> >>>>>>> Reviewed-by: David Gibson >>>>>>> >>>>>>>> --- >>>>>>>> v2: >>>>>>>> - fix NULL dereference caused by not initialized >>>>>>>> MachineState::cpu_type at the time parse_numa_opts() >>>>>>>> were called >>>>>>>> --- >>>>>>>> include/hw/boards.h | 2 ++ >>>>>>>> hw/arm/virt.c | 3 ++- >>>>>>>> hw/core/machine.c | 12 ++++++------ >>>>>>>> hw/i386/pc.c | 4 +++- >>>>>>>> hw/ppc/spapr.c | 13 ++++++++----- >>>>>>>> hw/s390x/s390-virtio-ccw.c | 1 + >>>>>>>> vl.c | 3 +-- >>>>>>>> 7 files changed, 23 insertions(+), 15 deletions(-) >>>>>>>> >>>>>>>> diff --git a/include/hw/boards.h b/include/hw/boards.h >>>>>>>> index 191a5b3..fa21758 100644 >>>>>>>> --- a/include/hw/boards.h >>>>>>>> +++ b/include/hw/boards.h >>>>>>>> @@ -80,6 +80,7 @@ void machine_set_cpu_numa_node(MachineState *machine, >>>>>>>> * CPUArchId: >>>>>>>> * @arch_id - architecture-dependent CPU ID of present or possible CPU >>>>>>> >>>>>>> I know this isn't really in scope for this patch, but is @arch_id here >>>>>>> supposed to have meaning defined by the target, or by the machine? >>>>>>> >>>>>>> If it's the machime, it could do with a rename - "arch" means target >>>>>>> to most people (thanks to Linux). >>>>>>> >>>>>>> If it's the target, it's kind of bogus, because it doesn't necessarily >>>>>>> have a clear meaning per target - get_arch_id in CPUClass has the same >>>>>>> problem, which is probably one reason it's basically only used by the >>>>>>> x86 code at present. >>>>>>> >>>>>>> e.g. for target/ppc, what do we use? There's the PIR, which is in the >>>>>>> CPU.. but only on some cpu models, not all. There will generally be >>>>>>> some kind of master PIC id, but there are different PIC models on >>>>>>> different boards. What goes in the devicetree? Well only some >>>>>>> machines use devicetree, and they might define the cpu reg >>>>>>> differently. >>>>>>> >>>>>>> Board designs will generally try to make some if not all of those >>>>>>> possible values equal for simplicity, but there's still no real way of >>>>>>> defining a sensible arch_id independent of machine / board. >>>>>> I'd say arch_id is machine specific so far, it was introduced when we >>>>>> didn't have CpuInstanceProperties and at that time we considered only >>>>>> vcpus (threads) and doesn't really apply to spapr cores. >>>>>> >>>>>> In general we could do away with arch_id and use CpuInstanceProperties >>>>>> instead, but arch_id also serves aux purpose, it allows machine to >>>>>> pre-calculate(cache) apic-id/mpidr values in one place and then they >>>>>> are/(could be) used by arch in-depended code to build acpi tables. >>>>>> So if we drop arch_id we would need to introduce a machine hook, >>>>>> which would translate CpuInstanceProperties into current arch_id. >>>>> >>>>> I think we need to do a better to job documenting where exactly >>>>> we expect arch_id to be used and how, so people know what it's >>>>> supposed to return. >>>>> >>>>> If the only place where it's useful now is ACPI code (is it?), >>>>> should we rename it to something like get_acpi_id()? >>>> >>>> It is also used in hw/s390x/sclp.c to fill out a control block, so acpi >>>> isn't the only user. >>> >>> Yeah.. this is kind of bogus. The s390 use is in machine specific >>> code, so it's basically just re-using the field for an unrelated usage >>> to the x86/arm one (ACPI). as index == arch_id on s390x, that code could easily be changed to something like: @@ -45,7 +45,7 @@ static void prepare_cpu_entries(SCLPDevice *sclp, CPUEntry *entry, int *count) if (!ms->possible_cpus->cpus[i].cpu) { continue; } - entry[*count].address = ms->possible_cpus->cpus[i].arch_id; + entry[*count].address = i; entry[*count].type = 0; memcpy(entry[*count].features, features, sizeof(features)); (*count)++; arch_id just looked like the right thing to use (documentation issue mentioned above) >>> >>> If we can't assign a universal meaning to the field (even if the >>> actual values are per-machine) - and I don't think we can - then I >>> really don't think it belongs in CPUState. A machine hook which >>> translates an ArchId to an acpi_id is the correct solution I believe. >>> Or even an ACPIMachine interface (to be implemented by machines which >>> do ACPI) which has a method to do this. >>> >>> Since both the assignment and use are in machine type specific code >>> for s390, it can have its own field in the s390 specific cpu subclass. s390x doesn't need arch_id at all. cs->cpu_index can be used. >>> >> >> I agree. This might require duplicating cpu_by_arch_id() and >> cpu_exists() into machine-specific code, but this doesn't sound >> too bad: there's only one user of cpu_by_arch_id() (that's >> x86-specific code living inside monitor.c), and one user of >> cpu_exists() (that's s390-specific code).>> >> (Maybe those users could be rewritten to use >> MachineState::possible_cpus, like pc_find_cpu_slot()). -- Thanks, David / dhildenb