On 10/26/17 17:13, Laszlo Ersek wrote: > Hello Julien, > > On 10/26/17 13:05, Julien Grall wrote: >> Hi all, >> >> I was doing more testing of UEFI in Xen guests and noticed some slow >> down when using the shell. The characters are only echoed after a second >> or two that is a bit annoying. >> >> The change that introduced this issue is 4cf3f37c87 "MdeModulePkg >> SerialDxe: Process timeout consistently in SerialRead". >> >> The Serial Driver for Xen PV console is very simple (see >> OvmfPkg/Library/XenConsoleSerialPortLib). So I am not sure where the >> root cause is. >> >> Would anyone have any tips on it? > > The exact same issue has been encountered earlier under QEMU, please > refer to the following sub-thread (please read it to end): > > http://mid.mail-archive.com/[email protected] > > The fix was commit 5f0f5e90ae8c ("ArmVirtPkg/FdtPL011SerialPortLib: call > PL011UartLib in all SerialPortLib APIs", 2017-08-16). > > I think if you can implement the same for XenConsoleSerialPortLib, that > should return to working state as well.
Hmmm, wait, at a closer look, it looks like OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c already implements that suggestion? (I.e., it sets EFI_SERIAL_INPUT_BUFFER_EMPTY in *Control as necessary?) Are we sure the SerialPortPoll() function works correctly? I don't see any MemoryFence() calls in SerialPortPoll(), around checking the fields in (*mXenConsoleInterface). Could that be the problem? Thanks, Laszlo > > ... This is why we need active Xen participants in edk2 ;) > > Thanks! > Laszlo > _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
