Re: [Xen-users] Does Xen HVM 32bit guest support SMP and PAE?

[psboy <psboy.liu@xxxxxxxxx>]

Hi Mats,
Thanks for your reply.

2006/12/4, Petersson, Mats <Mats.Petersson@xxxxxxx>:

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx ] On Behalf Of psboy
> Sent: 02 December 2006 13:34
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Does Xen HVM 32bit guest support SMP and PAE? 

That's unlikely to work, as there's no way to tell an "unkown" guest
that it's suddenly got a second CPU - you may have somewhat better luck

Maybe cpu hotplug? Although i don't think it will work.

with setting "vcpus=2" in the configuration file before you start the
DomU - although I'm not entirely sure that works right either - there's
certainly some fixed coming in 3.0.4 that will fix Windows SMP on ACPI
Hal.

But "xm vcpu-set Domain-0 2" work with Domain-0. (4 -> 2 CPUs in Domain-0 )
I can see Domain-0 actually set vCPUs as i want.
I also see Domain-0 CPUs reduce to 2 by "cat /proc/cpuinfo".
After that,i create a hvm guest domain with "vcpus=2" in config file but still fail.
xm list i see only ONE CPU.

> I can see another vcpu if use this command although another
> vcpu is in p state. (pause?)
> [root@xenunsvr xen]# xm vcpu-list
> Name                              ID VCPUs   CPU State
> Time(s) CPU Affinity
> Domain-0                           0     0     0   r--
> 680.6 any cpu
> Domain-0                           0     1     -   --p
> 26.2 any cpu
> Domain-0                           0     2     -   --p
> 4.4 any cpu
> Domain-0                           0     3     -   --p
> 4.3 any cpu
> w2k3                               4     0     3   -b-
> 14.5 any cpu
> w2k3                               4     1     -   --p
> 0.0 any cpu
>
> 2.Another question is PAE.
> I am sure Dom0 have built PAE support.
> If i set memory > 1536 in w2k3.hvm,
> hvm machine can not start.
> [root@xenunsvr xen]# xm list
> Name                                      ID Mem(MiB) VCPUs
> State   Time(s)
> Domain-0                                   0      255     1
> r-----    811.4
> w2k3                                       5     2048     1
> ------      0.0
>
> I have no idea why memory < =1536 can work but > 1536 can
> start hvm guest.
> I try to change hvm guest OS to RHEL AS4U4 but still got the
> same result....

Someone else said that 2048MB doesn't work right - not sure if it's
reported as a bug or not.

I don't know if 3.0.3 has the "dynamic mapping" that is necessary to map
more than around 2GB of memory (even in PAE-mode), as the limit is
essentially set by the amount of space allowed by the QEMU mappings,
which is a total of 3GB altogether, but since there are other "bits" of
memory allocated by QEMU, it will not allow you all of the 3GB for
"RAM", but some of the 3GB is used up for other purposes, which gives
you a bit more than 2GB of QEMU RAM-space if it's not got the "dynamic
mapping" feature.

So how do i use this feature?
Can i set this in hvm config file?
Or i need to rebuild and set something in Dom0 Kernel config file?

You should be able to see if you have PAE or not by "xm info|grep 32p",
which should list hvm-3.0-x86_32p, and also xen-3.0-x86_32p.

xm info|grep 32p
xen_caps               : xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p

I think it should be ok and Domain-0 can get total 8G memory if i do not use dom0_mem=262144 parameter.

Greets

WS Liu
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