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
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