From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: Laszlo Ersek <lersek@redhat.com>,
qemu devel list <qemu-devel@nongnu.org>
Cc: Eduardo Habkost <ehabkost@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Igor Mammedov <imammedo@redhat.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [PATCH 3/4] hw/i386: add facility to expose CPU topology over fw-cfg
Date: Tue, 8 Oct 2019 15:29:06 +0200 [thread overview]
Message-ID: <6f3792fe-9cf6-725a-3fbc-475fda5c22e3@redhat.com> (raw)
In-Reply-To: <20191008105259.5378-4-lersek@redhat.com>
Hi Laszlo,
On 10/8/19 12:52 PM, Laszlo Ersek wrote:
> FW_CFG_MAX_CPUS exposes the (exclusive) maximum APIC ID to guest firmware,
> due to historical reasons. That value is not useful to edk2, however. For
> supporting VCPU hotplug, edk2 needs:
>
> - the boot CPU count (already exposed in FW_CFG_NB_CPUS),
>
> - and the maximum foreseen CPU count (tracked in
> "MachineState.smp.max_cpus", but not currently exposed).
>
> Add a new fw-cfg file to expose "max_cpus".
>
> While at it, expose the rest of the topology too (die / core / thread
> counts), because I expect that the VCPU hotplug feature for OVMF will
> ultimately need those too, and the data size is not large. This is
> slightly complicated by the fact that the die count is specific to
> PCMachineState, but fw_cfg_arch_create() intends to be PC-independent (see
> commit 149c50cabcc4).
The X86 topology is generic to the architecture (not machine specific)
so it is well placed in fw_cfg_arch_create().
>
> For now, the feature is temporarily disabled.
I see you enable it in the PC machine in the next patch.
Do you plan to remove the 'expose_topology' argument and expose the key
later, or is this comment simply related to this patch?
Ah, now I see you disable it previous to pc-4.2, OK.
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1515
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
> hw/i386/fw_cfg.h | 30 +++++++++++++++++++++++++++++-
> hw/i386/fw_cfg.c | 26 ++++++++++++++++++++++++--
> hw/i386/pc.c | 4 ++--
> 3 files changed, 55 insertions(+), 5 deletions(-)
>
> diff --git a/hw/i386/fw_cfg.h b/hw/i386/fw_cfg.h
> index e0856a376996..d742435b9793 100644
> --- a/hw/i386/fw_cfg.h
> +++ b/hw/i386/fw_cfg.h
> @@ -18,9 +18,37 @@
> #define FW_CFG_E820_TABLE (FW_CFG_ARCH_LOCAL + 3)
> #define FW_CFG_HPET (FW_CFG_ARCH_LOCAL + 4)
>
> +/**
> + * FWCfgX86Topology: expose the X86 CPU topology to guest firmware over fw-cfg.
> + *
> + * All fields have little-endian encoding.
> + *
> + * @dies: Number of dies per package (aka socket). Set it to 1 unless the
> + * concrete MachineState subclass defines it differently.
> + * @cores: Corresponds to @CpuTopology.@cores.
> + * @threads: Corresponds to @CpuTopology.@threads.
> + * @max_cpus: Corresponds to @CpuTopology.@max_cpus.
> + *
> + * Firmware can derive the package (aka socket) count with the following
> + * formula:
> + *
> + * DIV_ROUND_UP(@max_cpus, @dies * @cores * @threads)
> + *
> + * Firmware can derive APIC ID field widths and offsets per the standard
> + * calculations in "include/hw/i386/topology.h".
> + */
> +typedef struct FWCfgX86Topology {
> + uint32_t dies;
> + uint32_t cores;
> + uint32_t threads;
> + uint32_t max_cpus;
> +} QEMU_PACKED FWCfgX86Topology;
> +
> FWCfgState *fw_cfg_arch_create(MachineState *ms,
> uint16_t boot_cpus,
> - uint16_t apic_id_limit);
> + uint16_t apic_id_limit,
> + unsigned smp_dies,
> + bool expose_topology);
> void fw_cfg_build_smbios(MachineState *ms, FWCfgState *fw_cfg);
> void fw_cfg_build_feature_control(MachineState *ms, FWCfgState *fw_cfg);
>
> diff --git a/hw/i386/fw_cfg.c b/hw/i386/fw_cfg.c
> index 39b6bc60520c..33d09875014f 100644
> --- a/hw/i386/fw_cfg.c
> +++ b/hw/i386/fw_cfg.c
> @@ -85,9 +85,26 @@ void fw_cfg_build_smbios(MachineState *ms, FWCfgState *fw_cfg)
> }
> }
>
> +static void fw_cfg_expose_topology(FWCfgState *fw_cfg,
> + unsigned dies,
> + unsigned cores,
> + unsigned threads,
> + unsigned max_cpus)
> +{
> + FWCfgX86Topology *topo = g_new(FWCfgX86Topology, 1);
> +
> + topo->dies = cpu_to_le32(dies);
> + topo->cores = cpu_to_le32(cores);
> + topo->threads = cpu_to_le32(threads);
> + topo->max_cpus = cpu_to_le32(max_cpus);
> + fw_cfg_add_file(fw_cfg, "etc/x86-smp-topology", topo, sizeof *topo);
> +}
> +
> FWCfgState *fw_cfg_arch_create(MachineState *ms,
> - uint16_t boot_cpus,
> - uint16_t apic_id_limit)
> + uint16_t boot_cpus,
> + uint16_t apic_id_limit,
> + unsigned smp_dies,
> + bool expose_topology)
> {
> FWCfgState *fw_cfg;
> uint64_t *numa_fw_cfg;
> @@ -143,6 +160,11 @@ FWCfgState *fw_cfg_arch_create(MachineState *ms,
> (1 + apic_id_limit + nb_numa_nodes) *
> sizeof(*numa_fw_cfg));
>
> + if (expose_topology) {
> + fw_cfg_expose_topology(fw_cfg, smp_dies, ms->smp.cores,
> + ms->smp.threads, ms->smp.max_cpus);
> + }
> +
> return fw_cfg;
> }
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index bcda50efcc23..bb72b12edad2 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1738,8 +1738,8 @@ void pc_memory_init(PCMachineState *pcms,
> option_rom_mr,
> 1);
>
> - fw_cfg = fw_cfg_arch_create(machine,
> - pcms->boot_cpus, pcms->apic_id_limit);
> + fw_cfg = fw_cfg_arch_create(machine, pcms->boot_cpus, pcms->apic_id_limit,
> + pcms->smp_dies, false);
>
> rom_set_fw(fw_cfg);
>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
next prev parent reply other threads:[~2019-10-08 13:30 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 10:52 [PATCH 0/4] hw/i386: pass "MachineState.smp.max_cpus" to OVMF Laszlo Ersek
2019-10-08 10:52 ` [PATCH 1/4] fw_cfg: bump file slots to 40 Laszlo Ersek
2019-10-08 10:52 ` [PATCH 2/4] target/i386: remove useless enable_compat_apic_id_mode() prototype Laszlo Ersek
2019-10-08 13:35 ` Philippe Mathieu-Daudé
2019-10-08 18:22 ` Laszlo Ersek
2019-10-08 10:52 ` [PATCH 3/4] hw/i386: add facility to expose CPU topology over fw-cfg Laszlo Ersek
2019-10-08 13:29 ` Philippe Mathieu-Daudé [this message]
2019-10-08 18:31 ` Laszlo Ersek
2019-10-08 15:59 ` Igor Mammedov
2019-10-09 21:01 ` Laszlo Ersek
2019-10-10 9:45 ` Igor Mammedov
2019-10-10 10:01 ` Michael S. Tsirkin
2019-10-10 12:48 ` Igor Mammedov
2019-10-10 16:23 ` Laszlo Ersek
2019-10-10 18:08 ` Michael S. Tsirkin
2019-10-11 6:50 ` Laszlo Ersek
2019-10-11 7:46 ` Laszlo Ersek
2019-10-10 16:15 ` Laszlo Ersek
2019-10-08 18:58 ` Laszlo Ersek
2019-10-09 11:13 ` Igor Mammedov
2019-10-09 21:03 ` Laszlo Ersek
2019-10-09 21:09 ` Eduardo Habkost
2019-10-08 10:52 ` [PATCH 4/4] hw/i386/pc: " Laszlo Ersek
2019-10-08 14:23 ` [PATCH 0/4] hw/i386: pass "MachineState.smp.max_cpus" to OVMF no-reply
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