[syslinux] "Tick-counting" vs "Tick-less" timekeeping issues on VMs emulating BIOS PCs

Patrick Masotta
Mon, 07 Mar 2016 15:50:40 -0000

>>>

...
Bottom line; There are timing issues with TFTP transfers
on VM machines emulating BIOS hardware.
Probably the interrupt based timer is not the culprit;
now I'm working on /core/fs/pxe/core.c trying to see if
there's something wrong there.

Best,

Patrick
<<<

I've been working on this issue, I have tested the timers,
and as you guys mentioned before they are OK.
I've noticed that if the VMware VM uses the driver e1000e everything is
"OK"
but if the VM uses the "vmxnet3" the problem is there.
I have attached a small pcap file showing the end of the lpxelinux.0 TFTP
transfer and the

beginning of the problematic ldlinux.c32 transfer.
I wonder if the "vmxnet3" driver is probably "too fast" for
the Sequential lwIP API?


Best,
Patrick
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