> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of psboy
> Sent: 04 December 2006 17:57
> To: Petersson, Mats
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Does Xen HVM 32bit guest support SMP and PAE?
>
> 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.
But there is, as far as I know, not pre-defined interface for ACPI
hot-plugging of processors (or memory for that matter). There is the
possibility to define an ACPI interface for it, but you also need to
have a suitable driver that responds to that ACPI interface, and that's
where we'd need a special Windows driver (or to replicate the hardware
of some hot-pluggable hardware).
>
>
>
> 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.
Dom0 is para-virtual, so it can talk to Xen, and for this purpose, Xen
can tell it to "Please remove two processors from yourself" - and I
believe this uses the Linux hotplug code with suitable Xenification.
I suspect that you need another set of fixes for the SMP information -
there's been a few fixes, and one of the features for 3.0.4 is listed as
" * SMP Windows HVM support with ACPI HAL" (that's directly from Keir
Fraser's mail).
You may want to try the current unstable - it is fairly stable and good
at the moemnt, as far as I know.
If two cpu's don't work "automatically" at that point, you probably
should file a bug on the Xen bugzilla so that the developers know that
it's not working as it should.
Note also that Windows needs to replace the HAL to be able to recognize
a second CPU, so it's best to install Windows with the wanted number of
processors (or at least two) from the first step, rather than trying to
change it later.
>
>
>
> > 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?
I saw a patch to enable this go in devel today, so I'm taking it as "it
doesn't exist yet". And note that the maximum you can allocate to QEMU
is "the large contiguous section of user-space memory", which means that
it may well be less than 2GB in many circumstances.
Once this patch is in it should work "automagically" (and I doubt that
it'll make it into 3.0.4, but there is a chance, as 3.0.4 is "frozen" at
the moment).
>
>
>
> 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.
Yes, that's correct.
If you limit Dom0 memory, bear in mind also that the amount of memory
used for page-tables may also limit the amount of space used by one
particular qemu instance - although I think 256MB should give you plenty
of space (you need 8 bytes per 4K of memory, so 2048MB should need 2048
* 256 * 8 bytes, which is 4MB of memory to be mapped.)
--
Mats
>
>
>
> Greets
>
> WS Liu
>
>
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