[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [v5][PATCH 10/16] tools: introduce some new parameters to set rdm policy

+"none" is the default value and it means we don't check any reserved regions
+and then all rdm policies would be ignored. Guest just works as before and
+the conflict of RDM and guest address space wouldn't be handled, and then
+this may result in the associated device not being able to work or even crash
+the VM. So if you're assigning this kind of device, this option is not
+recommended unless you can make sure any conflict doesn't exist.

One issue didn't come to conclusion during last round of review. Ian was
asking what's the difference with type=none vs not specifying rdm option
at all.

You need to either convince Ian or remove "type=none" in *xl* level.
I.e. don't touch the libxl IDL. It still needs a none type.

I'll update this next revision. And also rephrase this doc to address your comments below.


+For example, you're trying to set "memory = 2800" to allocate memory to one
+given VM but the platform owns two RDM regions like,
+RMRR region: base_addr ac6d3000 end_address ac6e6fff
+RMRR region: base_addr ad800000 end_address afffffff
+In this conflict case,
+#1. If the type options is set with "none",

If B<type> is set to "none", for example,

+rdm = "type=none,reserve=strict" or rdm = "type=none,reserve=relaxed"
+mean we don't handle any conflict just to make VM keep running as before.
+Note this is our default behavior.

It means we don't handle any conflict to make VM run as before. This is
the default behavior.

+#2. If the type options is set with "host",

If B<type> is set to "host", for example,

+rdm = "type=host,reserve=strict" or rdm = "type=host,reserve=relaxed"
+mean all conflict would be handled according to our policies which is
+introduced by the reserve option as described below.

It means all conflicts will be handled according to the policy
introduced by B<reserve> as described below.

+=item B<reserve="STRING">
+Specifies how to deal with conflicts discovered when reserving reserved device
+memory in the guest address space.

Specifies how to deal with conflicts when reserving reserved device
memory in guest address space.

+When that conflict is unsolved,
+"strict" means this VM can't be created successfully, or the associated device
+can't be attached in the case of hotplug;

"strict" means VM can't be created, or the associated device can't be
attached in the case of hotplug.

+"relaxed" allows a VM to be created to keep running with a warning message
+thrown out. But this may crash this VM if this device accesses RDM. For 
+Windows IGD GFX driver always access these regions so this lead to a blue 
+to crash VM in such a case.

"relaxed" allows VM to be created but may cause VM to crash if
pass-through device accesses RDM. For exampl,e Windows IGD GFX driver
always accessed RDM regions so it leads to VM crash.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.