Hi,
After registered invalid DRHDs, Xen hangs in boot time.
About RMRR, I understood the logic.
In my mainboard, unfortunately, RMRR has non-existent device under
its scope, and to make matters worse, the RMRR range is invalid.
So, I think RMRR that has no-existent device is valid.
How do you think about these?

Hi Noboru,
You should not ignore DRHD even if devices under its scope are not pci discoverable. For 
the sake of security, we still enable these DRHDs but don't set any context mappings. In 
that case, any DMA that comes from these "supposedly disabled" devices will get 
blocked by VT-d, and hence avoid any security vulnerability with malicious s/w 
re-enabling these devices.
You RMRR validity fixing is wrong. My RMRR patch is no problem. Pls note that 
the RMRR checking logic is:
 If all devices under RMRR's scope are not pci discoverable
 Ignore the RMRR
 Else if base_address> end_address
 Return error
 Else
 Register RMRR
Regards,
Weidong
 
-----Original Message-----
From: Noboru Iwamatsu [mailto:n_iwamatsu@xxxxxxxxxxxxxx]
Sent: Thursday, January 21, 2010 4:26 PM
To: Han, Weidong
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; keir.fraser@xxxxxxxxxxxxx
Subject: Re: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
Hi,
Some Q35 mainboard that has buggy BIOS, I have one of this, reports invalid 
DRHD in addition to the invalid RMRR.
Attached patch fixes this DRHD issue in the same way as RMRR.
And also, I fixed RMRR validity checking loop.
Noboru.
Signed-off-by: Noboru Iwamatsu<n_iwamatsu@xxxxxxxxxxxxxx>
-------- Original Message --------
Subject: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
From: Han, Weidong<weidong.han@xxxxxxxxx>
To: xen-devel@xxxxxxxxxxxxxxxxxxx<xen-devel@xxxxxxxxxxxxxxxxxxx>
Date: Thu Jan 21 2010 11:46:12 GMT+0900

Currently, Xen checks RMRR range and disables VT-d if RMRR range is set 
incorrectly in BIOS rigorously. But, actually we can ignore the RMRR if the 
device under its scope are not pci discoverable, because the RMRR won't be used 
by non-existed or disabled devices.
This patch ignores the RMRR if the device under its scope are not pci 
discoverable, and only checks the validity of RMRRs that are actually used. In 
order to avoid duplicate pci device detection code, this patch defines a 
function pci_device_detect for it.
Signed-off-by: Weidong Han<weidong.han@xxxxxxxxx>
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