Re: Xen Console input very slow in recent UEFI

[Laszlo Ersek <lersek@redhat.com>]

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/b748580c-cb51-32c9-acf9-780841ef15da@redhat.com

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.

... This is why we need active Xen participants in edk2 ;)

Thanks!
Laszlo