On Wed, Apr 15, 2020 at 04:04:35PM +0200, Laszlo Ersek wrote:
> On 04/14/20 20:01, Rebecca Cran wrote:
> > I was trying to build OvmfPkg/XenPkg -a X64 -t GCC5 -b DEBUG
> > -DDEBUG_ON_SERIAL_PORT=TRUE, but the build fails. Both plain DEBUG and
> > RELEASE builds without trying to put the debug output on the serial
> > port work.
> >
> >
> > [bcran@smic ~/src/tmp/edk2]$ build -p OvmfPkg/OvmfXen.dsc -a X64 -t
> > GCC5 -b DEBUG -DDEBUG_ON_SERIAL_PORT=TRUE
> > Build environment: FreeBSD-13.0-CURRENT-amd64-64bit-ELF
> > Build start time: 11:59:24, Apr.14 2020
> >
> > WORKSPACE = /home/bcran/src/tmp/edk2
> > EDK_TOOLS_PATH = /home/bcran/src/tmp/edk2/BaseTools
> > CONF_PATH = /home/bcran/src/tmp/edk2/Conf
> > PYTHON_COMMAND = /usr/local/bin/python3
> >
> >
> > Processing meta-data .
> > Architecture(s) = X64
> > Build target = DEBUG
> > Toolchain = GCC5
> >
> > Active Platform = /home/bcran/src/tmp/edk2/OvmfPkg/OvmfXen.dsc
> > .
> >
> > build.py...
> > /home/bcran/src/tmp/edk2/OvmfPkg/OvmfXen.dsc(...): error F002: Library
> > [/home/bcran/src/tmp/edk2/MdePkg/Library/UefiBootServicesTableLib/UefiBootServicesTableLib.inf]
> > with constructors has a cycle
> > consumed by
> > /home/bcran/src/tmp/edk2/MdePkg/Library/UefiLib/UefiLib.inf
> > consumed by
> > /home/bcran/src/tmp/edk2/MdePkg/Library/UefiDevicePathLibDevicePathProtocol/UefiDevicePathLibDevicePathProtocol.inf
>
> From commit 05480e2fd4ff ("OvmfPkg/PlatformBootManagerLib: Use a Xen
> console for ConOut/ConIn", 2019-08-21), we have:
>
> > diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc
> > index 54ac910d8eed..e719a168f81e 100644
> > --- a/OvmfPkg/OvmfXen.dsc
> > +++ b/OvmfPkg/OvmfXen.dsc
> > @@ -586,6 +586,10 @@ [Components]
> > OvmfPkg/XenIoPciDxe/XenIoPciDxe.inf
> > OvmfPkg/XenBusDxe/XenBusDxe.inf
> > OvmfPkg/XenPvBlkDxe/XenPvBlkDxe.inf
> > + MdeModulePkg/Universal/SerialDxe/SerialDxe.inf {
> > + <LibraryClasses>
> > +
> > SerialPortLib|OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf
> > + }
> > MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
> >
> > MdeModulePkg/Universal/MonotonicCounterRuntimeDxe/MonotonicCounterRuntimeDxe.inf
> > MdeModulePkg/Universal/CapsuleRuntimeDxe/CapsuleRuntimeDxe.inf
>
> If you run the "build" command with the "-v" option added, the last part
> (just preceding the error message above) is:
>
> > Library instances of module
> > [MdeModulePkg/Universal/SerialDxe/SerialDxe.inf] [X64]:
> > UefiDriverEntryPoint :
> > MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf
> > UefiBootServicesTableLib :
> > MdePkg/Library/UefiBootServicesTableLib/UefiBootServicesTableLib.inf
> > DebugLib :
> > MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf
> > PcdLib : MdePkg/Library/DxePcdLib/DxePcdLib.inf
> > SerialPortLib :
> > OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.inf
> > BaseLib : MdePkg/Library/BaseLib/BaseLib.inf
> > XenHypercallLib :
> > OvmfPkg/Library/XenHypercallLib/XenHypercallLib.inf
> > HobLib : MdePkg/Library/DxeHobLib/DxeHobLib.inf
> > BaseMemoryLib :
> > MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf
> > UefiLib : MdePkg/Library/UefiLib/UefiLib.inf
> > PrintLib : MdePkg/Library/BasePrintLib/BasePrintLib.inf
> > MemoryAllocationLib :
> > MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf
> > DevicePathLib :
> > MdePkg/Library/UefiDevicePathLibDevicePathProtocol/UefiDevicePathLibDevicePathProtocol.inf
> > UefiRuntimeServicesTableLib :
> > MdePkg/Library/UefiRuntimeServicesTableLib/UefiRuntimeServicesTableLib.inf
> > DebugPrintErrorLevelLib :
> > MdePkg/Library/BaseDebugPrintErrorLevelLib/BaseDebugPrintErrorLevelLib.inf
>
> The dependency loop is formed by:
>
> DebugLib : BaseDebugLibSerialPort ->
> SerialPortLib : XenConsoleSerialPortLib ->
> XenHypercallLib : XenHypercallLib ->
> DebugLib
>
> where all the library instances BaseDebugLibSerialPort,
> XenConsoleSerialPortLib, XenHypercallLib have constructors.
>
> Note that XenConsoleSerialPortLib *itself* is careful to avoid a
> DebugLib dependency; from "XenConsoleSerialPortLib.c":
>
> > //
> > // We can't use DebugLib due to a constructor dependency cycle between
> > DebugLib
> > // and ourselves.
> > //
> > #define ASSERT(Expression) \
> > do { \
> > if (!(Expression)) { \
> > CpuDeadLoop (); \
> > } \
> > } while (FALSE)
>
> However, XenConsoleSerialPortLib still inherits a DebugLib dependency
> through XenHypercallLib -- but only on IA32/X64, not on ARM/AARCH64! See
> "XenHypercallLib.inf":
>
> > [LibraryClasses.IA32, LibraryClasses.X64]
> > BaseLib
> > HobLib
> > DebugLib
>
> There is no issue without specifying DEBUG_ON_SERIAL_PORT, because
> OvmfXen resolves DebugLib to PlatformDebugLibIoPort then, which does not
> depend on SerialPortLib (thus the cycle is severed).
>
>
> Now, I think there may not be a simple solution for this, because, as
> the message on commit 05480e2fd4ff says, "On a Xen PVH guest, none of
> the existing serial or console interface works".
>
> So even if we eliminated the constructor cycle for this module -- i.e.,
> SerialDxe -- somehow [1], the larger DEBUG_ON_SERIAL_PORT feature might
> not be feasible for *some* module types in OvmfXen. Because,
> XenConsoleSerialPortLib ultimately depends on hypercalls, and I'm unsure
> if those could be used as early as in SEC / PEI.
>
> [1] For breaking up just this one constructor cycle, I guess we could
> remove the DebugLib dependency from XenHypercallLib even on
> IA32/X64.
>
> In other words, I'm not sure if you could send any DEBUG messages *at
> all* to the Xen serial port as early as in SEC or PEI. Meaning that even
> if DEBUG_ON_SERIAL_PORT didn't break the build, it still wouldn't
> (comprehensively) do what its name says.
>
> I figure you attempted the DEBUG_ON_SERIAL_PORT build because without it
> you get no debug output at all (due to the default
> PlatformDebugLibIoPort resolution, which produces no logs on Xen).
>
> For a start, I would recommend removing DEBUG_ON_SERIAL_PORT altogether
> from OvmfXen (to decrease confusion and to eliminate the build
> breakage), and then filing a feature request in the TianoCore bugzilla
> for "some" kind of debug logging in OvmfXen, if the latter is possible.
Thanks Laszlo for the investigation. I usually use DebugLib to debug
OVMF under Xen, I just need to enable the debug port of QEMU. And for
when QEMU isn't available (when running Xen PVH guest), I have a local
patch that I haven't send upstream yet. It's a hacked version of
PlatformDebugLibIoPort which sends logs to Xen's debug port, and doesn't
check if the port is open.
I'll prepare a patch to remove DEBUG_ON_SERIAL_PORT support from OvmfXen
and send my other patch.
Thanks,
--
Anthony PERARD
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