Re: [PATCH v6 3/9] OvmfPkg/CpuHotplugSmm: add Qemu Cpu Status helper

["Laszlo Ersek" <lersek@redhat.com>]

On 01/29/21 01:59, Ankur Arora wrote:
> Add QemuCpuhpWriteCpuStatus() which will be used to update the QEMU
> CPU status register. On error, it hangs in a similar fashion as
> other helper functions.
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Aaron Young <aaron.young@oracle.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> ---
>  OvmfPkg/CpuHotplugSmm/QemuCpuhp.h |  6 ++++++
>  OvmfPkg/CpuHotplugSmm/QemuCpuhp.c | 22 ++++++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h
> index 8adaa0ad91f0..804809846890 100644
> --- a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h
> +++ b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.h
> @@ -30,6 +30,12 @@ QemuCpuhpReadCpuStatus (
>    IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
>    );
>  
> +VOID
> +QemuCpuhpWriteCpuStatus (
> +  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
> +  IN UINT8                        CpuStatus
> +  );
> +
>  UINT32
>  QemuCpuhpReadCommandData (
>    IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
> diff --git a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c
> index f871e50c377b..ed44264de934 100644
> --- a/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c
> +++ b/OvmfPkg/CpuHotplugSmm/QemuCpuhp.c
> @@ -67,6 +67,28 @@ QemuCpuhpReadCpuStatus (
>    return CpuStatus;
>  }
>  
> +VOID
> +QemuCpuhpWriteCpuStatus (
> +  IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo,
> +  IN UINT8                        CpuStatus
> +  )
> +{
> +  EFI_STATUS Status;
> +
> +  Status = MmCpuIo->Io.Write (
> +                         MmCpuIo,
> +                         MM_IO_UINT8,
> +                         ICH9_CPU_HOTPLUG_BASE + QEMU_CPUHP_R_CPU_STAT,
> +                         1,
> +                         &CpuStatus
> +                         );
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a: %r\n", __FUNCTION__, Status));
> +    ASSERT (FALSE);
> +    CpuDeadLoop ();
> +  }
> +}
> +
>  UINT32
>  QemuCpuhpReadCommandData (
>    IN CONST EFI_MM_CPU_IO_PROTOCOL *MmCpuIo
> 

The code is fine, but please move the new function (both declaration and
definition) between QemuCpuhpWriteCpuSelector() and QemuCpuhpWriteCommand().

Reason: the pre-patch order of the functions matches the order of the
register descriptions in QEMU's "docs/specs/acpi_cpu_hotplug.txt".

There, we first have a section called "read access", then another called
"write access". And in each section, registers are listed in increasing
offset order, within the hotplug register block.

Thanks!
Laszlo