[RFC PATCH] OvmfPkg/PlatformCI VS2019: Enable temporary workaround for cpuhp bugfix

["Ard Biesheuvel" <ardb@kernel.org>]

QEMU for x86 has a nasty CPU hotplug bug of which the ramifications are
difficult to oversee, even though KVM acceleration seems to be
unaffected. This has been addressed in QEMU mainline, and will percolate
through the ecosystem at its usual pace. In the mean time, due to the
potential impact on production workloads, we will be updating OVMF to
abort the boot when it detects a QEMU build that is affected.

Tiancore's platform CI uses QEMU in TCG mode, and is therefore impacted
by this mitigation, unless its QEMU builds are updated. This has been
done for Ubuntu-GCC5, but Windows-VS2019 still uses a QEMU build that is
affected.

Aborting the boot upon detecting the QEMU issue will render all boot
tests carried out on Windows-VS2019 broken unless we implement the
'escape hatch' that enables proceed-at-your-own-risk mode, and permits
the boot to proceed even if the QEMU issue is detected.

So let's enable this for Windows-VS2019, and remove it again once it is
no longer needed.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Brown <mcb30@ipxe.org>
Cc: Oliver Steffen <osteffen@redhat.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>

Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml |  2 +-
 OvmfPkg/PlatformCI/PlatformBuildLib.py                | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml b/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
index 7e63f419b26b..b3b91aa84ea0 100644
--- a/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
+++ b/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
@@ -24,7 +24,7 @@ jobs:
       package: 'OvmfPkg'
       vm_image: 'windows-2019'
       should_run: true
-      run_flags: "MAKE_STARTUP_NSH=TRUE QEMU_HEADLESS=TRUE"
+      run_flags: "MAKE_STARTUP_NSH=TRUE QEMU_HEADLESS=TRUE QEMU_CPUHP_QUIRK=TRUE"
 
     #Use matrix to speed up the build process
     strategy:
diff --git a/OvmfPkg/PlatformCI/PlatformBuildLib.py b/OvmfPkg/PlatformCI/PlatformBuildLib.py
index bfef9849c749..58dc1189a2cc 100644
--- a/OvmfPkg/PlatformCI/PlatformBuildLib.py
+++ b/OvmfPkg/PlatformCI/PlatformBuildLib.py
@@ -170,6 +170,7 @@ class PlatformBuilder( UefiBuilder, BuildSettingsManager):
         self.env.SetValue("PRODUCT_NAME", "OVMF", "Platform Hardcoded")
         self.env.SetValue("MAKE_STARTUP_NSH", "FALSE", "Default to false")
         self.env.SetValue("QEMU_HEADLESS", "FALSE", "Default to false")
+        self.env.SetValue("QEMU_CPUHP_QUIRK", "FALSE", "Default to false")
         return 0
 
     def PlatformPreBuild(self):
@@ -211,6 +212,17 @@ class PlatformBuilder( UefiBuilder, BuildSettingsManager):
             args += " -pflash " + os.path.join(OutputPath_FV, "OVMF.fd")    # path to firmware
 
 
+        ###
+        ### NOTE This is a temporary workaround to allow platform CI to cope with
+        ###      a QEMU bug in the CPU hotplug code. Once the CI environment has
+        ###      been updated to carry a fixed version of QEMU, this can be
+        ###      removed again
+        ###
+        ### Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
+        ###
+        if (self.env.GetValue("QEMU_CPUHP_QUIRK").upper() == "TRUE"):
+            args += "  -fw_cfg name=opt/org.tianocore/X-Cpuhp-Bugcheck-Override,string=yes"
+
         if (self.env.GetValue("MAKE_STARTUP_NSH").upper() == "TRUE"):
             f = open(os.path.join(VirtualDrive, "startup.nsh"), "w")
             f.write("BOOT SUCCESS !!! \n")
-- 
2.39.0