The "virsh setvcpus" (plural) command may hot-plug several VCPUs in quick
succession -- it means a series of "device_add" QEMU monitor commands,
back-to-back.
If a "device_add" occurs *just before* ACPI raises the broadcast SMI,
then:
- OVMF processes the hot-added CPU well.
- However, QEMU's post-SMI ACPI loop -- which clears the pending events
for the hot-added CPUs that were collected before raising the SMI -- is
unaware of the stray CPU. Thus, the pending event is not cleared for it.
As a result of the stuck event, at the next hot-plug, OVMF tries to re-add
(relocate for the 2nd time) the already-known CPU. At that time, the AP is
already in the normal edk2 SMM busy-wait however, so it doesn't respond to
the exchange that the BSP intends to do in SmbaseRelocate(). Thus the VM
gets stuck in SMM.
(Because of the above symptom, this is not considered a security patch; it
doesn't seem exploitable by a malicious guest OS.)
In CpuHotplugMmi(), skip the supposedly hot-added CPU if it's already
known. The post-SMI ACPI loop will clear the pending event for it this
time.
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Fixes: bc498ac4ca
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2929
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200826222129.25798-2-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
With the help of the Post-SMM Pen and the SMBASE relocation functions
added in the previous patches, we can now complete the root MMI handler
for CPU hotplug.
In the driver's entry point function:
- allocate the pen (in a reserved page in normal RAM),
- install the default ("first") SMI handler for hot-added CPUs (which
includes priming the exchange area between the MM Monarch and the
hot-added CPUs, i.e., shutting the APIC ID gate).
In the root MMI handler, for each hot-added CPU:
- record the APIC ID of the new CPU in CPU_HOT_PLUG_DATA,
- relocate the SMBASE of the new CPU,
- inform PiSmmCpuDxeSmm by calling
EFI_SMM_CPU_SERVICE_PROTOCOL.AddProcessor().
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200226221156.29589-14-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Call QemuCpuhpCollectApicIds() in the root MMI handler. The APIC IDs of
the hotplugged CPUs will be used for several purposes in subsequent
patches.
For calling QemuCpuhpCollectApicIds(), pre-allocate both of its output
arrays "PluggedApicIds" and "ToUnplugApicIds" in the driver's entry point
function. The allocation size is dictated by the possible CPU count, which
we fetch from "CPU_HOT_PLUG_DATA.ArrayLength".
The CPU_HOT_PLUG_DATA structure in SMRAM is an out-of-band information
channel between this driver and PiSmmCpuDxeSmm, underlying
EFI_SMM_CPU_SERVICE_PROTOCOL.
In order to consume "CPU_HOT_PLUG_DATA.ArrayLength", extend the driver's
DEPEX to EFI_SMM_CPU_SERVICE_PROTOCOL. PiSmmCpuDxeSmm stores the address
of CPU_HOT_PLUG_DATA to "PcdCpuHotPlugDataAddress", before it produces
EFI_SMM_CPU_SERVICE_PROTOCOL.
Stash the protocol at once, as it will be needed later.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20200226221156.29589-11-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
