Re: [PATCH V13 4/8] hw/acpi: Update GED _EVT method AML with CPU scan

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 8 Jul 2024 05:21:06 +0000
Salil Mehta <salil.mehta@opnsrc.net> wrote:

> Hi Igor,
> 
> On 06/07/2024 14:28, Igor Mammedov wrote:
> > On Fri, 7 Jun 2024 12:56:45 +0100
> > Salil Mehta <salil.mehta@huawei.com> wrote:
> >  
> >> OSPM evaluates _EVT method to map the event. The CPU hotplug event eventually
> >> results in start of the CPU scan. Scan figures out the CPU and the kind of
> >> event(plug/unplug) and notifies it back to the guest. Update the GED AML _EVT
> >> method with the call to \\_SB.CPUS.CSCN
> >>
> >> Also, macro CPU_SCAN_METHOD might be referred in other places like during GED
> >> intialization so it makes sense to have its definition placed in some common
> >> header file like cpu_hotplug.h. But doing this can cause compilation break
> >> because of the conflicting macro definitions present in cpu.c and cpu_hotplug.c  
> > one of the reasons is that you reusing legacy hw/acpi/cpu_hotplug.h,
> > see below for suggestion.  
> ok
> >  
> >> and because both these files get compiled due to historic reasons of x86 world
> >> i.e. decision to use legacy(GPE.2)/modern(GED) CPU hotplug interface happens
> >> during runtime [1]. To mitigate above, for now, declare a new common macro
> >> ACPI_CPU_SCAN_METHOD for CPU scan method instead.
> >> (This needs a separate discussion later on for clean-up)
> >>
> >> Reference:
> >> [1] https://lore.kernel.org/qemu-devel/1463496205-251412-24-git-send-email-imammedo@redhat.com/
> >>
> >> Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
> >> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> >> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> >> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >> Reviewed-by: Gavin Shan <gshan@redhat.com>
> >> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> >> Tested-by: Xianglai Li <lixianglai@loongson.cn>
> >> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> >> Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> >> Tested-by: Zhao Liu <zhao1.liu@intel.com>
> >> ---
> >>   hw/acpi/cpu.c                  | 2 +-
> >>   hw/acpi/generic_event_device.c | 4 ++++
> >>   include/hw/acpi/cpu_hotplug.h  | 2 ++
> >>   3 files changed, 7 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> >> index 473b37ba88..af2b6655d2 100644
> >> --- a/hw/acpi/cpu.c
> >> +++ b/hw/acpi/cpu.c
> >> @@ -327,7 +327,7 @@ const VMStateDescription vmstate_cpu_hotplug = {
> >>   #define CPUHP_RES_DEVICE  "PRES"
> >>   #define CPU_LOCK          "CPLK"
> >>   #define CPU_STS_METHOD    "CSTA"
> >> -#define CPU_SCAN_METHOD   "CSCN"
> >> +#define CPU_SCAN_METHOD   ACPI_CPU_SCAN_METHOD
> >>   #define CPU_NOTIFY_METHOD "CTFY"
> >>   #define CPU_EJECT_METHOD  "CEJ0"
> >>   #define CPU_OST_METHOD    "COST"
> >> diff --git a/hw/acpi/generic_event_device.c b/hw/acpi/generic_event_device.c
> >> index 54d3b4bf9d..63226b0040 100644
> >> --- a/hw/acpi/generic_event_device.c
> >> +++ b/hw/acpi/generic_event_device.c
> >> @@ -109,6 +109,10 @@ void build_ged_aml(Aml *table, const char *name, HotplugHandler *hotplug_dev,
> >>                   aml_append(if_ctx, aml_call0(MEMORY_DEVICES_CONTAINER "."
> >>                                                MEMORY_SLOT_SCAN_METHOD));
> >>                   break;
> >> +            case ACPI_GED_CPU_HOTPLUG_EVT:
> >> +                aml_append(if_ctx, aml_call0(ACPI_CPU_CONTAINER "."
> >> +                                             ACPI_CPU_SCAN_METHOD));  
> > I don't particularly like exposing cpu hotplug internals for outside code
> > and then making that code do plumbing hoping that nothing will explode
> > in the future.  
> 
> I understand your point but I've followed what was already existing.
> 
> For example,
> 
> build_dsdt()
> 
> {
> 
>         [...]
> 
>      acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
>                         (irqmap[VIRT_UART] + ARM_SPI_BASE));
>      if (vmc->acpi_expose_flash) {
>          acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
>      }
>      fw_cfg_acpi_dsdt_add(scope, &memmap[VIRT_FW_CFG]);
>      virtio_acpi_dsdt_add(scope, memmap[VIRT_MMIO].base, 
> memmap[VIRT_MMIO].size,
>                           (irqmap[VIRT_MMIO] + ARM_SPI_BASE),
>                           0, NUM_VIRTIO_TRANSPORTS);
>      acpi_dsdt_add_pci(scope, memmap, irqmap[VIRT_PCIE] + ARM_SPI_BASE, 
> vms);
>      if (vms->acpi_dev) {
>          build_ged_aml(scope, "\\_SB."GED_DEVICE,
>                        HOTPLUG_HANDLER(vms->acpi_dev),
>                        irqmap[VIRT_ACPI_GED] + ARM_SPI_BASE, 
> AML_SYSTEM_MEMORY,
>                        memmap[VIRT_ACPI_GED].base);
>      } else {
>          acpi_dsdt_add_gpio(scope, &memmap[VIRT_GPIO],
>                             (irqmap[VIRT_GPIO] + ARM_SPI_BASE));
>      }
> 
>        [...]
> 
> }
> 
> Refactoring all of this code will create a noise in this patch-set.
> > build_cpus_aml() takes event_handler_method to create a method that
> > can be called by platform. What I suggest is to call that method here
> > instead of trying to expose CPU hotplug internals and manually building
> > call path here.
> > aka:
> >    build_cpus_aml(event_handler_method = PATH_TO_GED_DEVICE.CSCN)
> > and then call here
> >    aml_append(if_ctx, aml_call0(CSCN));
> > which will call  CSCN in GED scope, that was be populated by
> > build_cpus_aml() to do cpu scan properly without need to expose
> > cpu hotplug internal names and then trying to fixup conflicts caused by that.
> >
> > PS:
> > we should do the same for memory hotplug, we see in context above
> >  
> Although. I agree with your suggested change but I think this should be
> 
> carried in another patch-set.

I have to disagree with another patch-set on top as it introduces
unnecessary code changes, wich 'another patch-set' will put back.
(talking specifically about CPU hotplug)

Not to mention doing as it was suggested should reduce size of
your series and overall complexity.

> 
> Best, Salil.
> 
> >  
> >> +                break;
> >>               case ACPI_GED_PWR_DOWN_EVT:
> >>                   aml_append(if_ctx,
> >>                              aml_notify(aml_name(ACPI_POWER_BUTTON_DEVICE),
> >> diff --git a/include/hw/acpi/cpu_hotplug.h b/include/hw/acpi/cpu_hotplug.h
> >> index 48b291e45e..ef631750b4 100644
> >> --- a/include/hw/acpi/cpu_hotplug.h
> >> +++ b/include/hw/acpi/cpu_hotplug.h
> >> @@ -20,6 +20,8 @@
> >>   #include "hw/acpi/cpu.h"
> >>   
> >>   #define ACPI_CPU_HOTPLUG_REG_LEN 12
> >> +#define ACPI_CPU_SCAN_METHOD "CSCN"
> >> +#define ACPI_CPU_CONTAINER "\\_SB.CPUS"
> >>   
> >>   typedef struct AcpiCpuHotplug {
> >>       Object *device;  
>