Re: [edk2-devel] [PATCH v8 10/10] OvmfPkg/SmmControl2Dxe: negotiate CPU hot-unplug

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

On 02/22/21 08:19, Ankur Arora wrote:
> Advertise OVMF support for CPU hot-unplug and negotiate it
> if QEMU requests the feature.
> 
> 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>
> ---
> 
> Notes:
>     Addresses the following review comments:
>     (1,3) s/hot unplug/hot-unplug/
>     (2) Get rid of the reference to the made up ICH9_APM_CNT_CPU_HOT_UNPLUG
>     (4,6) Remove the artificial tie in between
>      ICH9_LPC_SMI_F_CPU_HOTPLUG, ICH9_LPC_SMI_F_CPU_HOT_UNPLUG.
>     (5) Fully spell out "SMI on CPU hot-unplug".
>     (7) Emit separate messages on negotiation (or not) of
>      ICH9_LPC_SMI_F_CPU_HOT_UNPLUG.
> 
>  OvmfPkg/SmmControl2Dxe/SmiFeatures.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/OvmfPkg/SmmControl2Dxe/SmiFeatures.c b/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
> index c9d875543205..b1d59a559dae 100644
> --- a/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
> +++ b/OvmfPkg/SmmControl2Dxe/SmiFeatures.c
> @@ -29,6 +29,12 @@
>  //
>  #define ICH9_LPC_SMI_F_CPU_HOTPLUG BIT1
>  
> +// The following bit value stands for "enable CPU hot-unplug, and inject an SMI
> +// with control value ICH9_APM_CNT_CPU_HOTPLUG upon hot-unplug", in the
> +// "etc/smi/supported-features" and "etc/smi/requested-features" fw_cfg files.
> +//
> +#define ICH9_LPC_SMI_F_CPU_HOT_UNPLUG BIT2
> +

(1) The comment formatting is inconsistent with the rest. The line right
after the (extant) "ICH9_LPC_SMI_F_CPU_HOTPLUG" macro definition should
be "//", and not an empty line.

In fact, this new hunk should not introduce any empty line.


>  //
>  // Provides a scratch buffer (allocated in EfiReservedMemoryType type memory)
>  // for the S3 boot script fragment to write to and read from.
> @@ -112,7 +118,8 @@ NegotiateSmiFeatures (
>    QemuFwCfgReadBytes (sizeof mSmiFeatures, &mSmiFeatures);
>  
>    //
> -  // We want broadcast SMI, SMI on CPU hotplug, and nothing else.
> +  // We want broadcast SMI, SMI on CPU hotplug, SMI on CPU hot-unplug
> +  // and nothing else.
>    //
>    RequestedFeaturesMask = ICH9_LPC_SMI_F_BROADCAST;
>    if (!MemEncryptSevIsEnabled ()) {
> @@ -120,8 +127,10 @@ NegotiateSmiFeatures (
>      // For now, we only support hotplug with SEV disabled.
>      //
>      RequestedFeaturesMask |= ICH9_LPC_SMI_F_CPU_HOTPLUG;
> +    RequestedFeaturesMask |= ICH9_LPC_SMI_F_CPU_HOT_UNPLUG;
>    }
>    mSmiFeatures &= RequestedFeaturesMask;
> +

(2) Spurious empty line addition (it's likely left over from removing
the earlier attempt to "be smarter than QEMU").

The rest seems fine.

Thanks!
Laszlo


>    QemuFwCfgSelectItem (mRequestedFeaturesItem);
>    QemuFwCfgWriteBytes (sizeof mSmiFeatures, &mSmiFeatures);
>  
> @@ -166,6 +175,13 @@ NegotiateSmiFeatures (
>        __FUNCTION__));
>    }
>  
> +  if ((mSmiFeatures & ICH9_LPC_SMI_F_CPU_HOT_UNPLUG) == 0) {
> +    DEBUG ((DEBUG_INFO, "%a: CPU hot-unplug not negotiated\n", __FUNCTION__));
> +  } else {
> +    DEBUG ((DEBUG_INFO, "%a: CPU hot-unplug with SMI negotiated\n",
> +      __FUNCTION__));
> +  }
> +
>    //
>    // Negotiation successful (although we may not have gotten the optimal
>    // feature set).
>