diff --git a/SOURCES/edk2-UefiCpuPkg-PiSmmCpuDxeSmm-pause-in-WaitForSemaphore-.patch b/SOURCES/edk2-UefiCpuPkg-PiSmmCpuDxeSmm-pause-in-WaitForSemaphore-.patch
new file mode 100644
index 0000000..a1700de
--- /dev/null
+++ b/SOURCES/edk2-UefiCpuPkg-PiSmmCpuDxeSmm-pause-in-WaitForSemaphore-.patch
@@ -0,0 +1,105 @@
+From 70c9d989107c6ac964bb437c5a4ea6ffe3214e45 Mon Sep 17 00:00:00 2001
+From: Miroslav Rezanina <mrezanin@redhat.com>
+Date: Mon, 10 Aug 2020 07:52:28 +0200
+Subject: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: pause in WaitForSemaphore() before
+ re-fetch
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+RH-Author: Laszlo Ersek <lersek@redhat.com>
+Message-id: <20200731141037.1941-2-lersek@redhat.com>
+Patchwork-id: 98121
+O-Subject: [RHEL-8.3.0 edk2 PATCH 1/1] UefiCpuPkg/PiSmmCpuDxeSmm: pause in WaitForSemaphore() before re-fetch
+Bugzilla: 1861718
+RH-Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>
+RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
+
+Most busy waits (spinlocks) in "UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c"
+already call CpuPause() in their loop bodies; see SmmWaitForApArrival(),
+APHandler(), and SmiRendezvous(). However, the "main wait" within
+APHandler():
+
+> //
+> // Wait for something to happen
+> //
+> WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);
+
+doesn't do so, as WaitForSemaphore() keeps trying to acquire the semaphore
+without pausing.
+
+The performance impact is especially notable in QEMU/KVM + OVMF
+virtualization with CPU overcommit (that is, when the guest has
+significantly more VCPUs than the host has physical CPUs). The guest BSP
+is working heavily in:
+
+ BSPHandler() [MpService.c]
+ PerformRemainingTasks() [PiSmmCpuDxeSmm.c]
+ SetUefiMemMapAttributes() [SmmCpuMemoryManagement.c]
+
+while the many guest APs are spinning in the "Wait for something to
+happen" semaphore acquisition, in APHandler(). The guest APs are
+generating useless memory traffic and saturating host CPUs, hindering the
+guest BSP's progress in SetUefiMemMapAttributes().
+
+Rework the loop in WaitForSemaphore(): call CpuPause() in every iteration
+after the first check fails. Due to Pause Loop Exiting (known as Pause
+Filter on AMD), the host scheduler can favor the guest BSP over the guest
+APs.
+
+Running a 16 GB RAM + 512 VCPU guest on a 448 PCPU host, this patch
+reduces OVMF boot time (counted until reaching grub) from 20-30 minutes to
+less than 4 minutes.
+
+The patch should benefit physical machines as well -- according to the
+Intel SDM, PAUSE "Improves the performance of spin-wait loops". Adding
+PAUSE to the generic WaitForSemaphore() function is considered a general
+improvement.
+
+Cc: Eric Dong <eric.dong@intel.com>
+Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
+Cc: Rahul Kumar <rahul1.kumar@intel.com>
+Cc: Ray Ni <ray.ni@intel.com>
+Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1861718
+Signed-off-by: Laszlo Ersek <lersek@redhat.com>
+Message-Id: <20200729185217.10084-1-lersek@redhat.com>
+Reviewed-by: Eric Dong <eric.dong@intel.com>
+(cherry picked from commit 9001b750df64b25b14ec45a2efa1361a7b96c00a)
+Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
+---
+ UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 18 +++++++++++-------
+ 1 file changed, 11 insertions(+), 7 deletions(-)
+
+diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+index 57e788c..4bcd217 100644
+--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
++++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+@@ -40,14 +40,18 @@ WaitForSemaphore (
+ {
+ UINT32 Value;
+
+- do {
++ for (;;) {
+ Value = *Sem;
+- } while (Value == 0 ||
+- InterlockedCompareExchange32 (
+- (UINT32*)Sem,
+- Value,
+- Value - 1
+- ) != Value);
++ if (Value != 0 &&
++ InterlockedCompareExchange32 (
++ (UINT32*)Sem,
++ Value,
++ Value - 1
++ ) == Value) {
++ break;
++ }
++ CpuPause ();
++ }
+ return Value - 1;
+ }
+
+--
+1.8.3.1
+
diff --git a/SPECS/edk2.spec b/SPECS/edk2.spec
index af7baac..b64298f 100644
--- a/SPECS/edk2.spec
+++ b/SPECS/edk2.spec
@@ -7,7 +7,7 @@ ExclusiveArch: x86_64 aarch64
Name: edk2
Version: %{GITDATE}git%{GITCOMMIT}
-Release: 2%{?dist}
+Release: 3%{?dist}
Summary: UEFI firmware for 64-bit virtual machines
Group: Applications/Emulators
License: BSD-2-Clause-Patent and OpenSSL and MIT
@@ -56,6 +56,8 @@ Patch28: edk2-OvmfPkg-QemuKernelLoaderFsDxe-suppress-error-on-no-k.patch
Patch29: edk2-OvmfPkg-GenericQemuLoadImageLib-log-Not-Found-at-INF.patch
# For bz#1844682 - silent build of edk2-aarch64 logs DEBUG_ERROR messages that don't actually report serious errors
Patch30: edk2-SecurityPkg-Tcg2Dxe-suppress-error-on-no-swtpm-in-si.patch
+# For bz#1861718 - Very slow boot when overcommitting CPU
+Patch31: edk2-UefiCpuPkg-PiSmmCpuDxeSmm-pause-in-WaitForSemaphore-.patch
# python3-devel and libuuid-devel are required for building tools.
@@ -505,6 +507,11 @@ true
%endif
%changelog
+* Mon Aug 10 2020 Miroslav Rezanina <mrezanin@redhat.com> - 20200602gitca407c7246bf-3.el8
+- edk2-UefiCpuPkg-PiSmmCpuDxeSmm-pause-in-WaitForSemaphore-.patch [bz#1861718]
+- Resolves: bz#1861718
+ (Very slow boot when overcommitting CPU)
+
* Wed Jun 24 2020 Miroslav Rezanina <mrezanin@redhat.com> - 20200602gitca407c7246bf-2.el8
- edk2-OvmfPkg-QemuKernelLoaderFsDxe-suppress-error-on-no-k.patch [bz#1844682]
- edk2-OvmfPkg-GenericQemuLoadImageLib-log-Not-Found-at-INF.patch [bz#1844682]