HI Igor,
Thank for you replying back.
> From: qemu-devel-bounces+salil.mehta=huawei.com@nongnu.org <qemu-
> devel-bounces+salil.mehta=huawei.com@nongnu.org> On Behalf Of Igor
> Mammedov
> Sent: Wednesday, November 6, 2024 9:01 AM
> To: Salil Mehta <salil.mehta@huawei.com>
>
> On Tue, 5 Nov 2024 21:12:00 +0000
> Salil Mehta <salil.mehta@huawei.com> wrote:
>
> > > From: Igor Mammedov <imammedo@redhat.com>
> > > Sent: Tuesday, November 5, 2024 12:50 PM
> > > To: Michael S. Tsirkin <mst@redhat.com>
> > > Cc: qemu-devel@nongnu.org; Peter Maydell
> > > <peter.maydell@linaro.org>; Salil Mehta <salil.mehta@huawei.com>;
> > > Ani Sinha <anisinha@redhat.com>; Eduardo Habkost
> > > <eduardo@habkost.net>; Marcel Apfelbaum
> > > <marcel.apfelbaum@gmail.com>; Philippe Mathieu-Daudé
> > > <philmd@linaro.org>; wangyanan (Y) <wangyanan55@huawei.com>;
> Zhao
> > > Liu <zhao1.liu@intel.com>
> > > Subject: Re: [PULL 60/65] hw/acpi: Update ACPI `_STA` method with
> > > QOM vCPU ACPI Hotplug states
> > >
> > > On Mon, 4 Nov 2024 16:09:26 -0500
> > > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > >
> > > > From: Salil Mehta <salil.mehta@huawei.com> > > Reflect the QOM
> > > vCPUs ACPI CPU hotplug states in the `_STA.Present` > and and
> > > `_STA.Enabled` bits when the guest kernel evaluates the ACPI >
> > > `_STA` method during initialization, as well as when vCPUs are >
> > > hot-plugged or hot-unplugged. If the CPU is present then the its >
> > > `enabled` status can be fetched using architecture-specific code [1].
> > > >
> > > > Reference:
> > > > [1] Example implementation of architecture-specific hook to fetch
> CPU
> > > > `enabled status
> > > > Link:
> > > > https://github.com/salil-
> > > mehta/qemu/commit/c0b416b11e5af6505e558866f0e
> > > > b6c9f3709173e
> > > >
> > > > Signed-off-by: Salil Mehta <salil.mehta@huawei.com> >
> > > Message-Id: <20241103102419.202225-4-salil.mehta@huawei.com>
> > > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com> >
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- >
> > > include/hw/core/cpu.h | 1 +
> > > > hw/acpi/cpu.c | 38 ++++++++++++++++++++++++++++++++++--
> --
> > > > 2 files changed, 35 insertions(+), 4 deletions(-) > > diff
> > > --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h index >
> > > e7de77dc6d..db8a6fbc6e 100644 > --- a/include/hw/core/cpu.h > +++
> > > b/include/hw/core/cpu.h > @@ -159,6 +159,7 @@ struct CPUClass {
> > > > void (*query_cpu_fast)(CPUState *cpu, CpuInfoFast *value);
> > > > int64_t (*get_arch_id)(CPUState *cpu);
> > > > bool (*cpu_persistent_status)(CPUState *cpu);
> > > > + bool (*cpu_enabled_status)(CPUState *cpu);
> > > > void (*set_pc)(CPUState *cpu, vaddr value);
> > > > vaddr (*get_pc)(CPUState *cpu);
> > > > int (*gdb_read_register)(CPUState *cpu, GByteArray *buf, int
> > > > reg); diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c index >
> > > 9b03b4292e..23443f09a5 100644 > --- a/hw/acpi/cpu.c > +++
> > > b/hw/acpi/cpu.c > @@ -50,6 +50,18 @@ void
> > > acpi_cpu_ospm_status(CPUHotplugState
> > > *cpu_st, ACPIOSTInfoList ***list)
> > > > }
> > > > }
> > > >
> > > > +static bool check_cpu_enabled_status(DeviceState *dev) {
> > > > + CPUClass *k = dev ? CPU_GET_CLASS(dev) : NULL;
> > > > + CPUState *cpu = CPU(dev);
> > > > +
> > > > + if (cpu && (!k->cpu_enabled_status || k-
> >cpu_enabled_status(cpu)))
> > > {
> > > > + return true;
> > > > + }
> > > > +
> > > > + return false;
> > > > +}
> > > > +
> > > > static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr,
> > > unsigned > size) {
> > > > uint64_t val = 0;
> > > > @@ -63,10 +75,11 @@ static uint64_t cpu_hotplug_rd(void *opaque,
> > > hwaddr addr, unsigned size)
> > > > cdev = &cpu_st->devs[cpu_st->selector];
> > > > switch (addr) {
> > > > case ACPI_CPU_FLAGS_OFFSET_RW: /* pack and return is_* fields
> */
> > > > - val |= cdev->cpu ? 1 : 0;
> > > > + val |= check_cpu_enabled_status(DEVICE(cdev->cpu)) ? 1 : 0;
> > > > val |= cdev->is_inserting ? 2 : 0;
> > > > val |= cdev->is_removing ? 4 : 0;
> > > > val |= cdev->fw_remove ? 16 : 0;
> > > > + val |= cdev->cpu ? 32 : 0;
> > > > trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
> > > > break;
> > > > case ACPI_CPU_CMD_DATA_OFFSET_RW:
> > > > @@ -349,6 +362,7 @@ const VMStateDescription
> vmstate_cpu_hotplug
> > > = { > #define CPU_REMOVE_EVENT "CRMV"
> > > > #define CPU_EJECT_EVENT "CEJ0"
> > > > #define CPU_FW_EJECT_EVENT "CEJF"
> > > > +#define CPU_PRESENT "CPRS"
> > > >
> > > > void build_cpus_aml(Aml *table, MachineState *machine,
> > > CPUHotplugFeatures opts,
> > > > build_madt_cpu_fn build_madt_cpu, hwaddr
> > > > base_addr, @@ -409,7 +423,9 @@ void build_cpus_aml(Aml *table,
> > > MachineState *machine, CPUHotplugFeatures opts,
> > > > aml_append(field, aml_named_field(CPU_EJECT_EVENT, 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(3));
> > > > + /* 1 if present, read only */
> > > > + aml_append(field, aml_named_field(CPU_PRESENT, 1));
> > > > + aml_append(field, aml_reserved_field(2));
> > > > aml_append(field, aml_named_field(CPU_COMMAND, 8));
> > > > aml_append(cpu_ctrl_dev, field);
> > > >
> > > > @@ -439,6 +455,7 @@ void build_cpus_aml(Aml *table,
> MachineState
> > > *machine, CPUHotplugFeatures opts,
> > > > Aml *ctrl_lock = aml_name("%s.%s", cphp_res_path,
> CPU_LOCK);
> > > > Aml *cpu_selector = aml_name("%s.%s", cphp_res_path,
> > > CPU_SELECTOR);
> > > > Aml *is_enabled = aml_name("%s.%s", cphp_res_path,
> > > > CPU_ENABLED);
> > > > + Aml *is_present = aml_name("%s.%s", cphp_res_path,
> > > > + CPU_PRESENT);
> > > > Aml *cpu_cmd = aml_name("%s.%s", cphp_res_path,
> > > CPU_COMMAND);
> > > > Aml *cpu_data = aml_name("%s.%s", cphp_res_path,
> CPU_DATA);
> > > > Aml *ins_evt = aml_name("%s.%s", cphp_res_path,
> > > > CPU_INSERT_EVENT); @@ -467,13 +484,26 @@ void
> build_cpus_aml(Aml
> > > *table, MachineState *machine, CPUHotplugFeatures opts,
> > > > {
> > > > Aml *idx = aml_arg(0);
> > > > Aml *sta = aml_local(0);
> > > > + Aml *ifctx2;
> > > > + Aml *else_ctx;
> > > >
> > > > aml_append(method, aml_acquire(ctrl_lock, 0xFFFF));
> > > > aml_append(method, aml_store(idx, cpu_selector));
> > > > aml_append(method, aml_store(zero, sta));
> > > > - ifctx = aml_if(aml_equal(is_enabled, one));
> > > > + ifctx = aml_if(aml_equal(is_present, one));
> > >
> > > very likely this will break hotplug on after migration to older QEMU.
> >
> >
> > The above are local variables and are not being migrated. These are
> > not the same as the earlier comment you provided here. I've removed
> > those `is_present,enabled` states to address your earlier concerns:
> > https://lore.kernel.org/qemu-
> devel/20241018163118.0ae01a84@imammedo.us
> > ers.ipa.redhat.com/
> >
> > State-1: Possible State of ACPI _STA (without patches)
> >
> > _STA.Present = 0
> > _STA.Enabled = 0
> >
> > _STA.Present = 1
> > _STA.Enabled = 1
> >
> > State-2: Possible State of ACPI _STA (with patches)
> >
> > _STA.Present = 0
> > _STA.Enabled = 0
> >
> > _STA.Present = 1
> > _STA.Enabled = 1
> >
> > _STA.Present = 1
> > _STA.Enabled = 0 [New return state which should not affect x86]
> >
> >
> > State-1 is subset of State-2. If vCPU HP feature is off on the newer
> > Qemu then, State-1 becomes proper subset of State-2.
> > Later is also the state of the older Qemu?
>
>
> here is AML change from the next patch:
>
> - If ((\_SB.PCI0.PRES.CPEN == One))
> - {
> - Local0 = 0x0F
> + If ((\_SB.PCI0.PRES.CPRS == One))
> + {
>
> 'enable check' branch is not taken unless presence is set.
> However on old qemu there is no presence bit in register block and it always
> 0, isn't it?
Thanks. I can see your point now. We can rearrange the check as follows:
If ((\_SB.PCI0.PRES.CPEN == One))
{
Local0 = 0x0F
}
+ Else
+ {
+ If ((\_SB.PCI0.PRES.CPRS == One))
+ {
+ Local0 = 0x0D
+ }
+ }
If you are okay then I'll send above change as a Fix to [PULL 60/65], [PULL 61/65]
Please confirm.
Many thanks!
Best regards
Salil.
>
> If above is true, the new _STA running on old QEMU after migration will
> always return 0 and thus break x86 cphp.
>
>
> + If ((\_SB.PCI0.PRES.CPEN == One))
> + {
> + Local0 = 0x0F
> + }
> + Else
> + {
> + Local0 = 0x0D
> + }
> }
>
> >
> >
> > > > {
> > > > - aml_append(ifctx, aml_store(aml_int(0xF), sta));
> > > > + ifctx2 = aml_if(aml_equal(is_enabled, one));
> > > > + {
> > > > + /* cpu is present and enabled */
> > > > + aml_append(ifctx2, aml_store(aml_int(0xF), sta));
> > > > + }
> > > > + aml_append(ifctx, ifctx2);
> > > > + else_ctx = aml_else();
> > > > + {
> > > > + /* cpu is present but disabled */
> > > > + aml_append(else_ctx, aml_store(aml_int(0xD), sta));
> > > > + }
> > > > + aml_append(ifctx, else_ctx);
> > > > }
> > > > aml_append(method, ifctx);
> > > > aml_append(method, aml_release(ctrl_lock));
> > >
> >
>