Re: [edk2-devel] [RFC PATCH] OvmfPkg/PlatformCI VS2019: Enable temporary workaround for cpuhp bugfix

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

On 1/20/23 10:54, Ard Biesheuvel wrote:
> On Fri, 20 Jan 2023 at 10:25, Laszlo Ersek <lersek@redhat.com> wrote:
>>
>> On 1/19/23 14:43, Ard Biesheuvel wrote:
>>> 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")
>>
>> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
>>
>> Technically speaking, can I merge this *prepended* to my v3 patch set
>> ([PATCH v3 0/2] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg
>> block regression), in the *same* PR?
>>
>> Because then I'll do that, saving us a bit of duplicated work.
>>
> 
> Yes, please go ahead and merge this if it is all ready to go. I won't
> get around to it to later this afternoon.
> 
>> I'll then also file the BZ for reverting this (once I know the commit
>> hash), for when a new QEMU is out for Windows -- whom should I assign
>> that BZ? Oliver or Ard?
>>
> 
> You can assign it to me. And please put Michael Kubacki on cc as well.
> 

https://bugzilla.tianocore.org/show_bug.cgi?id=4324

(I couldn't add Oliver to the CC list; AIUI, he's not managed to get a
BZ account just yet.)

Thanks!
Laszlo