On Thu, 26 Nov 2020 19:35:30 -0800 Ankur Arora <ankur.a.ar...@oracle.com> wrote:
> On 2020-11-26 4:46 a.m., Laszlo Ersek wrote: > > On 11/26/20 11:24, Ankur Arora wrote: > >> On 2020-11-24 4:25 a.m., Igor Mammedov wrote: > >>> If firmware negotiates ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT feature, > >>> OSPM on CPU eject will set bit #4 in CPU hotplug block for to be > >>> ejected CPU to mark it for removal by firmware and trigger SMI > >>> upcall to let firmware do actual eject. > >>> > >>> Signed-off-by: Igor Mammedov <imamm...@redhat.com> > >>> --- > >>> PS: > >>> - abuse 5.1 machine type for now to turn off unplug feature > >>> (it will be moved to 5.2 machine type once new merge window is open) > >>> --- > >>> include/hw/acpi/cpu.h | 2 ++ > >>> docs/specs/acpi_cpu_hotplug.txt | 11 +++++++++-- > >>> hw/acpi/cpu.c | 18 ++++++++++++++++-- > >>> hw/i386/acpi-build.c | 5 +++++ > >>> hw/i386/pc.c | 1 + > >>> hw/isa/lpc_ich9.c | 2 +- > >>> 6 files changed, 34 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h > >>> index 0eeedaa491..999caaf510 100644 > >>> --- a/include/hw/acpi/cpu.h > >>> +++ b/include/hw/acpi/cpu.h > >>> @@ -22,6 +22,7 @@ typedef struct AcpiCpuStatus { > >>> uint64_t arch_id; > >>> bool is_inserting; > >>> bool is_removing; > >>> + bool fw_remove; > >>> uint32_t ost_event; > >>> uint32_t ost_status; > >>> } AcpiCpuStatus; > >>> @@ -50,6 +51,7 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object > >>> *owner, > >>> typedef struct CPUHotplugFeatures { > >>> bool acpi_1_compatible; > >>> bool has_legacy_cphp; > >>> + bool fw_unplugs_cpu; > >>> const char *smi_path; > >>> } CPUHotplugFeatures; > >>> diff --git a/docs/specs/acpi_cpu_hotplug.txt > >>> b/docs/specs/acpi_cpu_hotplug.txt > >>> index 9bb22d1270..f68ef6e06c 100644 > >>> --- a/docs/specs/acpi_cpu_hotplug.txt > >>> +++ b/docs/specs/acpi_cpu_hotplug.txt > >>> @@ -57,7 +57,11 @@ read access: > >>> It's valid only when bit 0 is set. > >>> 2: Device remove event, used to distinguish device for which > >>> no device eject request to OSPM was issued. > >>> - 3-7: reserved and should be ignored by OSPM > >>> + 3: reserved and should be ignored by OSPM > >>> + 4: if set to 1, OSPM requests firmware to perform device > >>> eject, > >>> + firmware shall clear this event by writing 1 into it > >>> before > >>> + performing device eject> + 5-7: reserved and > >>> should be ignored by OSPM > >>> [0x5-0x7] reserved > >>> [0x8] Command data: (DWORD access) > >>> contains 0 unless value last stored in 'Command field' is > >>> one of: > >>> @@ -82,7 +86,10 @@ write access: > >>> selected CPU device > >>> 3: if set to 1 initiates device eject, set by OSPM when it > >>> triggers CPU device removal and calls _EJ0 method > >>> - 4-7: reserved, OSPM must clear them before writing to > >>> register > >>> + 4: if set to 1 OSPM hands over device eject to firmware, > >>> + Firmware shall issue device eject request as described > >>> above > >>> + (bit #3) and OSPM should not touch device eject bit (#3), > >>> + 5-7: reserved, OSPM must clear them before writing to > >>> register > >>> [0x5] Command field: (1 byte access) > >>> value: > >>> 0: selects a CPU device with inserting/removing events and > >>> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c > >>> index f099b50927..09d2f20dae 100644 > >>> --- a/hw/acpi/cpu.c > >>> +++ b/hw/acpi/cpu.c > >>> @@ -71,6 +71,7 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr > >>> addr, unsigned size) > >>> val |= cdev->cpu ? 1 : 0; > >>> val |= cdev->is_inserting ? 2 : 0; > >>> val |= cdev->is_removing ? 4 : 0; > >>> + val |= cdev->fw_remove ? 16 : 0; > >> > >> I might be missing something but I don't see where cdev->fw_remove is being > >> set. > > > > See just below, in the cpu_hotplug_wr() hunk. When bit#4 is written -- > > which happens through the ACPI code change --, fw_remove is inverted. > Thanks that makes sense. I was reading the AML building code all wrong. > > > > > > >> We do set cdev->is_removing in acpi_cpu_unplug_request_cb() so AFAICS > >> we would always end up setting this bit: > >>> val |= cdev->is_removing ? 4 : 0; > >> > >> Also, if cdev->fw_remove and cdev->is_removing are both true, val would be > >> (4 | 16). I'm guessing that in that case the AML determines which case gets > >> handled but it might make sense to set just one of these? > > > > "is_removing" is set directly in response to the device_del QMP command. > > That QMP command is asynchronous to the execution of the guest OS. > > j > > "fw_remove" is set (by virtue of inverting) by ACPI CEJ0, which is > > executed by the guest OS's ACPI interpreter, after the guest OS has > > de-scheduled all processes from the CPU being removed (= basically after > > the OS has willfully forgotten about the CPU). > > > > Therefore, considering the bitmask (is_removing, fw_remove), three > > variations make sense: > > Just annotating these with the corresponding ACPI code to make sure > I have it straight. Please correct if my interpretation is wrong. Also, > a few questions inline: > > > > > #1 (is_removing=0, fw_remove=0) -- normal status; no unplug requested > > > > #2 (is_removing=1, fw_remove=0) -- unplug requested via QMP, guest OS > > is processing the request > > Guest executes the CSCN method and reads rm_evt (bit 2) (thus noticing > the is_removing=1), and then notifies the CPU to be removed via the > CTFY method. > > ifctx = aml_if(aml_equal(rm_evt, one)); > { > aml_append(ifctx, > aml_call2(CPU_NOTIFY_METHOD, uid, eject_req)); > aml_append(ifctx, aml_store(one, rm_evt)); > aml_append(ifctx, aml_store(one, has_event)); > } > > Then it does a store to rm_evt (bit 2). That would result in clearing > of is_removing. (Igor mentions that in a separate mail.) > > 1. Do we need to clear is_removing at all? AFAICS, it's only useful as > an ack to QEMU and I can't think of why that's useful. OTOH it > doesn't serve any useful purpose once the guest OS has seen the request. no firmware doesn't need to care about it, it's consumed by OSPM only > 2. Would it make sense to clear it first and then call CPU_NOTIFY_METHOD? > CPU_NOTIFY_METHOD (or _EJ0, COST) don't depend on is_removing but > that might change in the future. all methods are protected by be same mutex, so if _EJ0 is called while CSCN in progress it will wait till CSCN is finished. But clearing bit #2 before Notify should work too. > The notify would end up in calling acpi_hotplug_schedule() which would be > responsible for queuing work (on CPU0) to detach+unplug the CPU. > > Once the OS level detach succeeds, the worker evaluates the "_EJ0" method > which would do the actual CPU_EJECT_METHOD work. > > If the detach fails then it evaluates the CPU_OST_METHOD which updates > the status for the event and the status. > > At this point the state is back to: > > (is_removing=0, fw_remove=0) if OSPM fails to release CPU for whatever reasons, it's valid state, we just notify user using OST event that requested unplug wasn't successful. > > > #3 (is_removing=1, fw_remove=1) -- guest OS removed all references from > > the CPU, firmware is permitted / > > required to forget about the CPU as > > well, and then unplug the CPU > > CPU_EJECT_METHOD will do a store to bit 4, which would invert (and > thus set) fw_remove and then do the SMI. > > So, this would be > > #3 (is_removing=0, fw_remove=1) > > At this point the firmware calls QemuCPUhpCollectApicIds() which > (after changes) notices CPU(s) with fw_remove set. > > Collects them and does a store to bit 4, which would clear fw_remove. I'd skip this step on firmware side and make QEMU clear it when CPU is ejected. > > > > > #4 (is_removing=1, fw_remove=0) -- fimware is about to unplug the CPU > > > > #5 (is_removing=0, fw_remove=0) -- firmware performing unplug > Firmware does an unplug and writes to bit 3, thus clearing is_removing. > > On return from the firmware the guest evaluates the COST again. it's optional and depends on OSPM implementation (some do not call it on success) > And, eventually goes back to the CSCN where it processes more > hotplug or unplug events. CSCN in case of unplug finishes first, and only after that EJ0 calls are processed > > The variation (is_removing=0, fw_remove=1) is invalid / unused. > > /nods > > > > > > The firmware may be investigating the CPU register block between steps > > #2 and #3 -- in other words, the firmware may see a CPU for which > > is_remove is set (unplug requested via QMP), but the OS has not vacated > > yet (fw_remove=0). In that case, the firmware must just skip the CPU -- > > once the OS is done, it will set fw_remove too, and raise another SMI. > Yeah, it makes sense for the firmware to only care about a CPU once it > sees fw_remove=1. (And as currently situated, the firmware would never > see is_removing=1 at all.) > > > Thanks > Ankur > > > > > > >> > >> > >>> trace_cpuhp_acpi_read_flags(cpu_st->selector, val); > >>> break; > >>> case ACPI_CPU_CMD_DATA_OFFSET_RW: > >>> @@ -148,6 +149,8 @@ static void cpu_hotplug_wr(void *opaque, hwaddr > >>> addr, uint64_t data, > >>> hotplug_ctrl = qdev_get_hotplug_handler(dev); > >>> hotplug_handler_unplug(hotplug_ctrl, dev, NULL); > >>> object_unparent(OBJECT(dev)); > >>> + } else if (data & 16) { > >>> + cdev->fw_remove = !cdev->fw_remove; > >>> } > >>> break; > >>> case ACPI_CPU_CMD_OFFSET_WR: > >>> @@ -332,6 +335,7 @@ const VMStateDescription vmstate_cpu_hotplug = { > >>> #define CPU_INSERT_EVENT "CINS" > >>> #define CPU_REMOVE_EVENT "CRMV" > >>> #define CPU_EJECT_EVENT "CEJ0" > >>> +#define CPU_FW_EJECT_EVENT "CEJF" > >>> void build_cpus_aml(Aml *table, MachineState *machine, > >>> CPUHotplugFeatures opts, > >>> hwaddr io_base, > >>> @@ -384,7 +388,10 @@ void build_cpus_aml(Aml *table, MachineState > >>> *machine, CPUHotplugFeatures opts, > >>> aml_append(field, aml_named_field(CPU_REMOVE_EVENT, 1)); > >>> /* initiates device eject, write only */ > >>> aml_append(field, aml_named_field(CPU_EJECT_EVENT, 1)); > >>> - aml_append(field, aml_reserved_field(4)); > >>> + aml_append(field, aml_reserved_field(1)); > >>> + /* tell firmware to do device eject, write only */ > >>> + aml_append(field, aml_named_field(CPU_FW_EJECT_EVENT, 1)); > >>> + aml_append(field, aml_reserved_field(2)); > >>> aml_append(field, aml_named_field(CPU_COMMAND, 8)); > >>> aml_append(cpu_ctrl_dev, field); > >>> @@ -419,6 +426,7 @@ void build_cpus_aml(Aml *table, MachineState > >>> *machine, CPUHotplugFeatures opts, > >>> Aml *ins_evt = aml_name("%s.%s", cphp_res_path, > >>> CPU_INSERT_EVENT); > >>> Aml *rm_evt = aml_name("%s.%s", cphp_res_path, > >>> CPU_REMOVE_EVENT); > >>> Aml *ej_evt = aml_name("%s.%s", cphp_res_path, > >>> CPU_EJECT_EVENT); > >>> + Aml *fw_ej_evt = aml_name("%s.%s", cphp_res_path, > >>> CPU_FW_EJECT_EVENT); > >>> aml_append(cpus_dev, aml_name_decl("_HID", > >>> aml_string("ACPI0010"))); > >>> aml_append(cpus_dev, aml_name_decl("_CID", > >>> aml_eisaid("PNP0A05"))); > >>> @@ -461,7 +469,13 @@ void build_cpus_aml(Aml *table, MachineState > >>> *machine, CPUHotplugFeatures opts, > >>> aml_append(method, aml_acquire(ctrl_lock, 0xFFFF)); > >>> aml_append(method, aml_store(idx, cpu_selector)); > >>> - aml_append(method, aml_store(one, ej_evt)); > >>> + if (opts.fw_unplugs_cpu) { > >>> + aml_append(method, aml_store(one, fw_ej_evt)); > >>> + aml_append(method, > >>> aml_store(aml_int(OVMF_CPUHP_SMI_CMD), > >>> + aml_name("%s", opts.smi_path))); > >>> + } else { > >>> + aml_append(method, aml_store(one, ej_evt)); > >>> + } > >> My knowledge of AML is rather rudimentary but this looks mostly > >> reasonable to me. > >> > >> One question: the corresponding code for CPU hotplug does not send an > >> SMI_CMD. > >> Why the difference? > > > > This code (on eject) is executing *after* the OS kernel has processed > > the event. But on hotplug, the ordering is different (it must be): in > > that case, the CSCN (scan) method first notifies the firmware, and then > > the OS. > > > > Thanks > > Laszlo > > > >> > >> aml_append(while_ctx, > >> aml_store(aml_derefof(aml_index(new_cpus, > >> cpu_idx)), > >> uid)); > >> aml_append(while_ctx, > >> aml_call2(CPU_NOTIFY_METHOD, uid, dev_chk)); > >> aml_append(while_ctx, aml_store(uid, cpu_selector)); > >> aml_append(while_ctx, aml_store(one, ins_evt)); > >> aml_append(while_ctx, aml_increment(cpu_idx)); > >> > >> > >>> aml_append(method, aml_release(ctrl_lock)); > >>> } > >>> aml_append(cpus_dev, method); > >>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > >>> index 1f5c211245..475e76f514 100644 > >>> --- a/hw/i386/acpi-build.c > >>> +++ b/hw/i386/acpi-build.c > >>> @@ -96,6 +96,7 @@ typedef struct AcpiPmInfo { > >>> bool s4_disabled; > >>> bool pcihp_bridge_en; > >>> bool smi_on_cpuhp; > >>> + bool smi_on_cpu_unplug; > >>> bool pcihp_root_en; > >>> uint8_t s4_val; > >>> AcpiFadtData fadt; > >>> @@ -197,6 +198,7 @@ static void acpi_get_pm_info(MachineState > >>> *machine, AcpiPmInfo *pm) > >>> pm->pcihp_io_base = 0; > >>> pm->pcihp_io_len = 0; > >>> pm->smi_on_cpuhp = false; > >>> + pm->smi_on_cpu_unplug = false; > >>> assert(obj); > >>> init_common_fadt_data(machine, obj, &pm->fadt); > >>> @@ -220,6 +222,8 @@ static void acpi_get_pm_info(MachineState > >>> *machine, AcpiPmInfo *pm) > >>> pm->cpu_hp_io_base = ICH9_CPU_HOTPLUG_IO_BASE; > >>> pm->smi_on_cpuhp = > >>> !!(smi_features & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT)); > >>> + pm->smi_on_cpu_unplug = > >>> + !!(smi_features & > >>> BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT)); > >>> } > >>> /* The above need not be conditional on machine type because > >>> the reset port > >>> @@ -1582,6 +1586,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > >>> CPUHotplugFeatures opts = { > >>> .acpi_1_compatible = true, .has_legacy_cphp = true, > >>> .smi_path = pm->smi_on_cpuhp ? "\\_SB.PCI0.SMI0.SMIC" : > >>> NULL, > >>> + .fw_unplugs_cpu = pm->smi_on_cpu_unplug, > >>> }; > >>> build_cpus_aml(dsdt, machine, opts, pm->cpu_hp_io_base, > >>> "\\_SB.PCI0", "\\_GPE._E02"); > >>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c > >>> index 17b514d1da..2952a00fe6 100644 > >>> --- a/hw/i386/pc.c > >>> +++ b/hw/i386/pc.c > >>> @@ -99,6 +99,7 @@ > >>> GlobalProperty pc_compat_5_1[] = { > >>> { "ICH9-LPC", "x-smi-cpu-hotplug", "off" }, > >>> + { "ICH9-LPC", "x-smi-cpu-hotunplug", "off" }, > >>> }; > >>> const size_t pc_compat_5_1_len = G_N_ELEMENTS(pc_compat_5_1); > >>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c > >>> index 087a18d04d..8c667b7166 100644 > >>> --- a/hw/isa/lpc_ich9.c > >>> +++ b/hw/isa/lpc_ich9.c > >>> @@ -770,7 +770,7 @@ static Property ich9_lpc_properties[] = { > >>> DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState, > >>> smi_host_features, > >>> ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT, true), > >>> DEFINE_PROP_BIT64("x-smi-cpu-hotunplug", ICH9LPCState, > >>> smi_host_features, > >>> - ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, false), > >>> + ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, true), > >>> DEFINE_PROP_END_OF_LIST(), > >>> }; > >>> > >> > >> Thanks for sending out the patch btw. This helped me crystallize some of > >> the > >> corresponding OVMF code. > >> > >> Ankur > >> > >