[PATCH 0/2] UefiCpuPkg/MpInitLib: recover from a lost Start-up IPI #VSTOR-146639

["Denis V. Lunev" <den@openvz.org>]

WaitApWakeup() spins until an AP clears its wakeup signal, with no timeout
and no way out. A hypervisor can lose the Start-up IPI: KVM latches INIT
while the target vCPU is in SMM but discards the SIPI outright. The AP is
left in wait-for-SIPI, the BSP spins forever, and the guest never boots.

Analysis of the live hung guest is in the bug.

Patch 1 exports SendStartupIpi() from LocalApicLib, so one AP can be poked
without an INIT that would reset an AP already running the procedure.
Patch 2 makes WaitApWakeup() resend rather than spin.

Verified by dropping Start-up IPIs in KVM with a kprobe on
kvm_apic_send_ipi(); both firmware binaries are unmodified. Killing one
INIT-SIPI-SIPI sequence hangs the current firmware at all 8 drop points
tried, leaving the APs at CR0=0x00000010. The patched firmware boots at
all 8, issuing exactly one directed Start-up IPI per stranded AP. Without
injection, 80 boots patched against stock show no regression.

Submitted upstream as https://github.com/tianocore/edk2/pull/13164

Denis V. Lunev (2):
  UefiCpuPkg: add SendStartupIpi to LocalApicLib #VSTOR-146639
  UefiCpuPkg/MpInitLib: resend the Start-up IPI when an AP misses it
    #VSTOR-146639

 UefiCpuPkg/Include/Library/LocalApicLib.h     | 19 +++++
 .../Library/BaseXApicLib/BaseXApicLib.c       | 32 +++++--
 .../BaseXApicX2ApicLib/BaseXApicX2ApicLib.c   | 32 +++++--
 UefiCpuPkg/Library/MpInitLib/MpLib.c          | 85 +++++++++++++++++--
 UefiCpuPkg/Library/MpInitLib/MpLib.h          |  2 +
 5 files changed, 153 insertions(+), 17 deletions(-)

-- 
2.53.0