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

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

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.

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?

Thanks!
Laszlo