[Xen-devel] [Bug] Intel RMRR support with upstream Qemu

["Zhang, Xiong Y" <xiong.y.zhang@xxxxxxxxx>]

On an intel skylake machine with upstream qemu, if I add “rdm=strategy=host, policy=strict” to hvm.cfg, win 8.1 DomU couldn’t boot up and continues reboot.

 

Steps to reproduce this issue:

1)       Boot xen with iommu=1 to enable iommu

2)       hvm.cfg contain:

builder=”hvm”

memory=xxxx

disk=[‘win8.1 img’]

device_model_override=’qemu-system-i386’

device_model_version=’qemu-xen’

rdm=”strategy=host,policy=strict”

3)       xl cr hvm.cfg

 

Conditions to reproduce this issue:

1)       DomU memory size > the top address of RMRR. Otherwise, this issue will disappear.

2)       rdm=” strategy=host,policy=strict” should exist

3)       Windows DomU.  Linux DomU doesn’t have such issue.

4)       Upstream qemu.  Traditional qemu doesn’t have such issue.

 

In this situation, hvmloader will relocate some guest ram below RMRR to high memory, and it seems window guest access an invalid address.

Could someone give me some suggestions on how to debug this ?

 

thanks

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