HVM hypercalls

HVM hypercalls

[Ruslan Nikolaev]

Hi

I need to use hypercalls from HVM domain (e.g. HYPERVISOR_add_to_physmap). However, it does not work when I am trying to invoke it from HVM Linux guest. Basically, I don't see that anything happens on hypervisor's side. I also grep'ed the guest code for 'vmmcall'/'vmcall' and did not find anything. Is it possible to do it at all? Is it possible to make hypercalls from HVM domains or are they simply used for tools responsible to load HVM domain? Also, are they allowed (if allowed at all) from stubdom, ioemu, or both configurations?

I am using latest Xen version (xen-4.0.1-rc). I also tried both official Linux distribution as an HVM domain and the version from Xen repositary. The computer has Nehalem processor with VMX.

Thanks,
Ruslan.

RE: HVM hypercalls

[Dan Magenheimer]

Xen only allows certain hypercalls from an HVM guest
and the list is kept in tables in arch/x86/hvm/hvm.c.
See http://xenbits.xensource.com/xen-unstable.hg?rev/72c6228b5f0f 
for an example of adding an existing hypercall so that
it will be sent through to Xen.  Note that there is
no guarantee that any particular hypercall will work
properly from an HVM guest... this is just the mechanism
for getting a hypercall to be allowed by Xen.

> -----Original Message-----
> From: Ruslan Nikolaev [mailto:nruslan_devel@yahoo.com]
> Sent: Wednesday, July 28, 2010 1:23 PM
> To: xen-devel@lists.xensource.com
> Subject: [Xen-devel] HVM hypercalls
> 
> Hi
> 
> I need to use hypercalls from HVM domain (e.g.
> HYPERVISOR_add_to_physmap). However, it does not work when I am trying
> to invoke it from HVM Linux guest. Basically, I don't see that anything
> happens on hypervisor's side. I also grep'ed the guest code for
> 'vmmcall'/'vmcall' and did not find anything. Is it possible to do it
> at all? Is it possible to make hypercalls from HVM domains or are they
> simply used for tools responsible to load HVM domain? Also, are they
> allowed (if allowed at all) from stubdom, ioemu, or both
> configurations?
> 
> I am using latest Xen version (xen-4.0.1-rc). I also tried both
> official Linux distribution as an HVM domain and the version from Xen
> repositary. The computer has Nehalem processor with VMX.
> 
> Thanks,
> Ruslan.
> 
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

Re: HVM hypercalls

[Juergen Gross]

On 07/28/2010 09:22 PM, Ruslan Nikolaev wrote:
> Hi
>
> I need to use hypercalls from HVM domain (e.g. HYPERVISOR_add_to_physmap). However, it does not work when I am trying to invoke it from HVM Linux guest. Basically, I don't see that anything happens on hypervisor's side. I also grep'ed the guest code for 'vmmcall'/'vmcall' and did not find anything. Is it possible to do it at all? Is it possible to make hypercalls from HVM domains or are they simply used for tools responsible to load HVM domain? Also, are they allowed (if allowed at all) from stubdom, ioemu, or both configurations?
>
> I am using latest Xen version (xen-4.0.1-rc). I also tried both official Linux distribution as an HVM domain and the version from Xen repositary. The computer has Nehalem processor with VMX.

This should work.
We are using hypercalls from HVM domains without any problem on xen 3.3 and
4.0, one of them being HYPERVISOR_add_to_physmap. There must be something
you are doing wrong.

The following steps are required:

- use the cpuid instruction to search for Xen signature. You should begin with
   index 0x40000000 and look for the text "XenVMMXenVMM" in the returned
   registers ebx, ecx and edx. Increment the index by 0x100 up to 0x40001000 if
   necessary.
- get the xen msr register number via cpuid with index 0x40000x002 (x from
   step 1). The msr register number will be in register ebx.
- write the physical address of a 4k page to the obtained msr register via
   wrmsr. This page will be used by the hypervisor to write the appropriate
   code for the hypercalls to.
- each entry in that page occupies 32 bytes. You can do a specific hypercall
   by calling the function at the specific entry with the hypercall number as
   index


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@ts.fujitsu.com
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

Re: HVM hypercalls

[Ruslan Nikolaev]

Thank you very much! I'll try this. BTW is it required to do this for every module with HVM hypercalls or there is some shared initialization code in HVM guest (Linux) similar to one used in paravirtualized guests?

If it's supposed to be in a module, is there any good example I can look at?

AFAIK hypercall_page is being initialized on Xen side with appropriate vmcall/vmmcall code. Is this CPUID mechanism a standard way to obtain hypercall_page reference on HVM domain?

Thank you!
Ruslan.

--- On Thu, 7/29/10, Juergen Gross <juergen.gross@ts.fujitsu.com> wrote:

> From: Juergen Gross <juergen.gross@ts.fujitsu.com>
> Subject: Re: [Xen-devel] HVM hypercalls
> To: "Ruslan Nikolaev" <nruslan_devel@yahoo.com>
> Cc: xen-devel@lists.xensource.com
> Date: Thursday, July 29, 2010, 11:30 AM
> On 07/28/2010 09:22 PM, Ruslan
> Nikolaev wrote:
> > Hi
> > 
> > I need to use hypercalls from HVM domain (e.g.
> HYPERVISOR_add_to_physmap). However, it does not work when I
> am trying to invoke it from HVM Linux guest. Basically, I
> don't see that anything happens on hypervisor's side. I also
> grep'ed the guest code for 'vmmcall'/'vmcall' and did not
> find anything. Is it possible to do it at all? Is it
> possible to make hypercalls from HVM domains or are they
> simply used for tools responsible to load HVM domain? Also,
> are they allowed (if allowed at all) from stubdom, ioemu, or
> both configurations?
> > 
> > I am using latest Xen version (xen-4.0.1-rc). I also
> tried both official Linux distribution as an HVM domain and
> the version from Xen repositary. The computer has Nehalem
> processor with VMX.
> 
> This should work.
> We are using hypercalls from HVM domains without any
> problem on xen 3.3 and
> 4.0, one of them being HYPERVISOR_add_to_physmap. There
> must be something
> you are doing wrong.
> 
> The following steps are required:
> 
> - use the cpuid instruction to search for Xen signature.
> You should begin with
>   index 0x40000000 and look for the text
> "XenVMMXenVMM" in the returned
>   registers ebx, ecx and edx. Increment the index by
> 0x100 up to 0x40001000 if
>   necessary.
> - get the xen msr register number via cpuid with index
> 0x40000x002 (x from
>   step 1). The msr register number will be in register
> ebx.
> - write the physical address of a 4k page to the obtained
> msr register via
>   wrmsr. This page will be used by the hypervisor to
> write the appropriate
>   code for the hypercalls to.
> - each entry in that page occupies 32 bytes. You can do a
> specific hypercall
>   by calling the function at the specific entry with
> the hypercall number as
>   index
> 
> 
> Juergen
> 
> -- Juergen Gross           
>      Principal Developer Operating
> Systems
> TSP ES&S SWE OS6         
>          
>    Telephone: +49 (0) 89 3222 2967
> Fujitsu Technology Solutions       
>       e-mail: juergen.gross@ts.fujitsu.com
> Domagkstr. 28           
>            
>    Internet: ts.fujitsu.com
> D-80807 Muenchen           
>      Company details:
> ts.fujitsu.com/imprint.html
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 

Re: HVM hypercalls

[Jeremy Fitzhardinge]

  On 07/29/2010 11:55 AM, Ruslan Nikolaev wrote:
> Thank you very much! I'll try this. BTW is it required to do this for every module with HVM hypercalls or there is some shared initialization code in HVM guest (Linux) similar to one used in paravirtualized guests?
>
> If it's supposed to be in a module, is there any good example I can look at?
>
> AFAIK hypercall_page is being initialized on Xen side with appropriate vmcall/vmmcall code. Is this CPUID mechanism a standard way to obtain hypercall_page reference on HVM domain?

What kernel are you working with?  There's already code to implement 
pv-on-hvm support for various recent pvops kernels, so you can just base 
your work on those.

     J

Re: HVM hypercalls

[Ruslan Nikolaev]

I have 2 kernels:

1. From Xen repositary pvops-git (2.6.31.13).
2. From kernel.org: 2.6.32.16

Thank you!
Ruslan.


--- On Thu, 7/29/10, Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> From: Jeremy Fitzhardinge <jeremy@goop.org>
> Subject: Re: [Xen-devel] HVM hypercalls
> To: "Ruslan Nikolaev" <nruslan_devel@yahoo.com>
> Cc: xen-devel@lists.xensource.com
> Date: Thursday, July 29, 2010, 11:47 PM
>  On 07/29/2010 11:55 AM, Ruslan
> Nikolaev wrote:
> > Thank you very much! I'll try this. BTW is it required
> to do this for every module with HVM hypercalls or there is
> some shared initialization code in HVM guest (Linux) similar
> to one used in paravirtualized guests?
> > 
> > If it's supposed to be in a module, is there any good
> example I can look at?
> > 
> > AFAIK hypercall_page is being initialized on Xen side
> with appropriate vmcall/vmmcall code. Is this CPUID
> mechanism a standard way to obtain hypercall_page reference
> on HVM domain?
> 
> What kernel are you working with?  There's already
> code to implement pv-on-hvm support for various recent pvops
> kernels, so you can just base your work on those.
> 
>     J
> 
> 

Re: HVM hypercalls

[Jeremy Fitzhardinge]

  On 07/30/2010 09:06 AM, Ruslan Nikolaev wrote:
> I have 2 kernels:
>
> 1. From Xen repositary pvops-git (2.6.31.13).

You want 2.6.32.16 from xen.git - the branch is xen/stable-2.6.32.x

     J

> 2. From kernel.org: 2.6.32.16
>
> Thank you!
> Ruslan.
>
>
> --- On Thu, 7/29/10, Jeremy Fitzhardinge<jeremy@goop.org>  wrote:
>
>> From: Jeremy Fitzhardinge<jeremy@goop.org>
>> Subject: Re: [Xen-devel] HVM hypercalls
>> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
>> Cc: xen-devel@lists.xensource.com
>> Date: Thursday, July 29, 2010, 11:47 PM
>>   On 07/29/2010 11:55 AM, Ruslan
>> Nikolaev wrote:
>>> Thank you very much! I'll try this. BTW is it required
>> to do this for every module with HVM hypercalls or there is
>> some shared initialization code in HVM guest (Linux) similar
>> to one used in paravirtualized guests?
>>> If it's supposed to be in a module, is there any good
>> example I can look at?
>>> AFAIK hypercall_page is being initialized on Xen side
>> with appropriate vmcall/vmmcall code. Is this CPUID
>> mechanism a standard way to obtain hypercall_page reference
>> on HVM domain?
>>
>> What kernel are you working with?  There's already
>> code to implement pv-on-hvm support for various recent pvops
>> kernels, so you can just base your work on those.
>>
>>      J
>>
>>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

Re: HVM hypercalls

[Ruslan Nikolaev]

I've just tried to configure newever version (2.6.32.16) from repositary. However, boot fails because no root device is found. I am using disk image (the line in HVM config is disk = [ 'file:/home/ruslan/fs1.img,hda,w' ])
I also tried to compile kernel with 'blktap' driver which is disabled in default kernel config, but it does not help.

The previous version (2.6.31.13) worked fine with the same disk image and default configuration.

Thanks,
Ruslan.

--- On Sat, 7/31/10, Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> From: Jeremy Fitzhardinge <jeremy@goop.org>
> Subject: Re: [Xen-devel] HVM hypercalls
> To: "Ruslan Nikolaev" <nruslan_devel@yahoo.com>
> Cc: xen-devel@lists.xensource.com
> Date: Saturday, July 31, 2010, 4:07 AM
>   On 07/30/2010 09:06 AM, Ruslan
> Nikolaev wrote:
> > I have 2 kernels:
> >
> > 1. From Xen repositary pvops-git (2.6.31.13).
> 
> You want 2.6.32.16 from xen.git - the branch is
> xen/stable-2.6.32.x
> 
>      J
> 
> > 2. From kernel.org: 2.6.32.16
> >
> > Thank you!
> > Ruslan.
> >
> >
> > --- On Thu, 7/29/10, Jeremy Fitzhardinge<jeremy@goop.org> 
> wrote:
> >
> >> From: Jeremy Fitzhardinge<jeremy@goop.org>
> >> Subject: Re: [Xen-devel] HVM hypercalls
> >> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
> >> Cc: xen-devel@lists.xensource.com
> >> Date: Thursday, July 29, 2010, 11:47 PM
> >>   On 07/29/2010 11:55 AM, Ruslan
> >> Nikolaev wrote:
> >>> Thank you very much! I'll try this. BTW is it
> required
> >> to do this for every module with HVM hypercalls or
> there is
> >> some shared initialization code in HVM guest
> (Linux) similar
> >> to one used in paravirtualized guests?
> >>> If it's supposed to be in a module, is there
> any good
> >> example I can look at?
> >>> AFAIK hypercall_page is being initialized on
> Xen side
> >> with appropriate vmcall/vmmcall code. Is this
> CPUID
> >> mechanism a standard way to obtain hypercall_page
> reference
> >> on HVM domain?
> >>
> >> What kernel are you working with?  There's
> already
> >> code to implement pv-on-hvm support for various
> recent pvops
> >> kernels, so you can just base your work on those.
> >>
> >>      J
> >>
> >>
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel
> >
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 

Re: HVM hypercalls

[Jeremy Fitzhardinge]

  On 08/03/2010 12:48 PM, Ruslan Nikolaev wrote:
> I've just tried to configure newever version (2.6.32.16) from repositary. However, boot fails because no root device is found. I am using disk image (the line in HVM config is disk = [ 'file:/home/ruslan/fs1.img,hda,w' ])
> I also tried to compile kernel with 'blktap' driver which is disabled in default kernel config, but it does not help.

What is your root= parameter?  If you're using pv-on-hvm drivers, then 
the device will be named /dev/xvd[a-d] (for the moment).  It's very 
strongly recommended that you don't use a device-based root name (ie, 
use LABEL= UUID= or LVM for your root device) so that your config is 
failsafe against root device name changes.

     J

> The previous version (2.6.31.13) worked fine with the same disk image and default configuration.
>
> Thanks,
> Ruslan.
>
> --- On Sat, 7/31/10, Jeremy Fitzhardinge<jeremy@goop.org>  wrote:
>
>> From: Jeremy Fitzhardinge<jeremy@goop.org>
>> Subject: Re: [Xen-devel] HVM hypercalls
>> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
>> Cc: xen-devel@lists.xensource.com
>> Date: Saturday, July 31, 2010, 4:07 AM
>>    On 07/30/2010 09:06 AM, Ruslan
>> Nikolaev wrote:
>>> I have 2 kernels:
>>>
>>> 1. From Xen repositary pvops-git (2.6.31.13).
>> You want 2.6.32.16 from xen.git - the branch is
>> xen/stable-2.6.32.x
>>
>>       J
>>
>>> 2. From kernel.org: 2.6.32.16
>>>
>>> Thank you!
>>> Ruslan.
>>>
>>>
>>> --- On Thu, 7/29/10, Jeremy Fitzhardinge<jeremy@goop.org>
>> wrote:
>>>> From: Jeremy Fitzhardinge<jeremy@goop.org>
>>>> Subject: Re: [Xen-devel] HVM hypercalls
>>>> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
>>>> Cc: xen-devel@lists.xensource.com
>>>> Date: Thursday, July 29, 2010, 11:47 PM
>>>>     On 07/29/2010 11:55 AM, Ruslan
>>>> Nikolaev wrote:
>>>>> Thank you very much! I'll try this. BTW is it
>> required
>>>> to do this for every module with HVM hypercalls or
>> there is
>>>> some shared initialization code in HVM guest
>> (Linux) similar
>>>> to one used in paravirtualized guests?
>>>>> If it's supposed to be in a module, is there
>> any good
>>>> example I can look at?
>>>>> AFAIK hypercall_page is being initialized on
>> Xen side
>>>> with appropriate vmcall/vmmcall code. Is this
>> CPUID
>>>> mechanism a standard way to obtain hypercall_page
>> reference
>>>> on HVM domain?
>>>>
>>>> What kernel are you working with?  There's
>> already
>>>> code to implement pv-on-hvm support for various
>> recent pvops
>>>> kernels, so you can just base your work on those.
>>>>
>>>>        J
>>>>
>>>>
>>>
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xensource.com
>>> http://lists.xensource.com/xen-devel
>>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>>
>
>
>

Re: HVM hypercalls

[Ruslan Nikolaev]

Yes, I tried this but it does not seem to work. BTW in paravirtualized mode it works fine, the problem is only with HVM.

I tried to specify root=/dev/xvda (my disk image has no partitions, entire disk image is a single file system).

My config is (I also tried to comment out device model but it does not help):

import os, re
arch = os.uname()[4]
if re.search('64', arch):
    arch_libdir = 'lib64'
else:
    arch_libdir = 'lib'

kernel = "/usr/lib/xen/boot/hvmloader"

builder='hvm'

vcpus=1

memory = 1024
shadow_memory = 8
name = "xenhvm1"
disk = [ 'file:/home/ruslan/fs1.img,xvda,w' ]
device_model = '/usr/' + arch_libdir + '/xen/bin/qemu-dm'
# boot on floppy (a), hard disk (c) or CD-ROM (d)
# default: hard disk, cd-rom, floppy
boot="c"

sdl=1
vnc=0
vncviewer=0
vncpasswd=''
stdvga=1
serial='pty'
usbdevice='tablet'

Thanks,
Ruslan

--- On Wed, 8/4/10, Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> From: Jeremy Fitzhardinge <jeremy@goop.org>
> Subject: Re: [Xen-devel] HVM hypercalls
> To: "Ruslan Nikolaev" <nruslan_devel@yahoo.com>
> Cc: xen-devel@lists.xensource.com
> Date: Wednesday, August 4, 2010, 1:40 AM
>   On 08/03/2010 12:48 PM, Ruslan
> Nikolaev wrote:
> > I've just tried to configure newever version
> (2.6.32.16) from repositary. However, boot fails because no
> root device is found. I am using disk image (the line in HVM
> config is disk = [ 'file:/home/ruslan/fs1.img,hda,w' ])
> > I also tried to compile kernel with 'blktap' driver
> which is disabled in default kernel config, but it does not
> help.
> 
> What is your root= parameter?  If you're using
> pv-on-hvm drivers, then 
> the device will be named /dev/xvd[a-d] (for the
> moment).  It's very 
> strongly recommended that you don't use a device-based root
> name (ie, 
> use LABEL= UUID= or LVM for your root device) so that your
> config is 
> failsafe against root device name changes.
> 
>      J
> 
> > The previous version (2.6.31.13) worked fine with the
> same disk image and default configuration.
> >
> > Thanks,
> > Ruslan.
> >
> > --- On Sat, 7/31/10, Jeremy Fitzhardinge<jeremy@goop.org> 
> wrote:
> >
> >> From: Jeremy Fitzhardinge<jeremy@goop.org>
> >> Subject: Re: [Xen-devel] HVM hypercalls
> >> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
> >> Cc: xen-devel@lists.xensource.com
> >> Date: Saturday, July 31, 2010, 4:07 AM
> >>    On 07/30/2010 09:06 AM, Ruslan
> >> Nikolaev wrote:
> >>> I have 2 kernels:
> >>>
> >>> 1. From Xen repositary pvops-git (2.6.31.13).
> >> You want 2.6.32.16 from xen.git - the branch is
> >> xen/stable-2.6.32.x
> >>
> >>       J
> >>
> >>> 2. From kernel.org: 2.6.32.16
> >>>
> >>> Thank you!
> >>> Ruslan.
> >>>
> >>>
> >>> --- On Thu, 7/29/10, Jeremy Fitzhardinge<jeremy@goop.org>
> >> wrote:
> >>>> From: Jeremy Fitzhardinge<jeremy@goop.org>
> >>>> Subject: Re: [Xen-devel] HVM hypercalls
> >>>> To: "Ruslan Nikolaev"<nruslan_devel@yahoo.com>
> >>>> Cc: xen-devel@lists.xensource.com
> >>>> Date: Thursday, July 29, 2010, 11:47 PM
> >>>>     On 07/29/2010
> 11:55 AM, Ruslan
> >>>> Nikolaev wrote:
> >>>>> Thank you very much! I'll try this.
> BTW is it
> >> required
> >>>> to do this for every module with HVM
> hypercalls or
> >> there is
> >>>> some shared initialization code in HVM
> guest
> >> (Linux) similar
> >>>> to one used in paravirtualized guests?
> >>>>> If it's supposed to be in a module, is
> there
> >> any good
> >>>> example I can look at?
> >>>>> AFAIK hypercall_page is being
> initialized on
> >> Xen side
> >>>> with appropriate vmcall/vmmcall code. Is
> this
> >> CPUID
> >>>> mechanism a standard way to obtain
> hypercall_page
> >> reference
> >>>> on HVM domain?
> >>>>
> >>>> What kernel are you working with? 
> There's
> >> already
> >>>> code to implement pv-on-hvm support for
> various
> >> recent pvops
> >>>> kernels, so you can just base your work on
> those.
> >>>>
> >>>>        J
> >>>>
> >>>>
> >>>
> >>>
> >>>
> _______________________________________________
> >>> Xen-devel mailing list
> >>> Xen-devel@lists.xensource.com
> >>> http://lists.xensource.com/xen-devel
> >>>
> >>
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@lists.xensource.com
> >> http://lists.xensource.com/xen-devel
> >>
> >
> >
> >
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 

Re: HVM hypercalls

[Christoph Egger]

On Wednesday 04 August 2010 19:41:20 Ruslan Nikolaev wrote:
> Yes, I tried this but it does not seem to work. BTW in paravirtualized mode
> it works fine, the problem is only with HVM.
>
> I tried to specify root=/dev/xvda (my disk image has no partitions, entire
> disk image is a single file system).
>
> My config is (I also tried to comment out device model but it does not
> help):

You can simplify your guest config file:


> import os, re
> arch = os.uname()[4]
> if re.search('64', arch):
>     arch_libdir = 'lib64'
> else:
>     arch_libdir = 'lib'

Remove this part.

> kernel = "/usr/lib/xen/boot/hvmloader"

kernel = "hvmloader"

> builder='hvm'
>
> vcpus=1
>
> memory = 1024
> shadow_memory = 8
> name = "xenhvm1"
> disk = [ 'file:/home/ruslan/fs1.img,xvda,w' ]
> device_model = '/usr/' + arch_libdir + '/xen/bin/qemu-dm'

device_model = "qemu-dm"

> # boot on floppy (a), hard disk (c) or CD-ROM (d)
> # default: hard disk, cd-rom, floppy
> boot="c"
>
> sdl=1
> vnc=0
> vncviewer=0
> vncpasswd=''
> stdvga=1
> serial='pty'
> usbdevice='tablet'


Christoph



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Re: HVM hypercalls

[Stefano Stabellini]

On Wed, 4 Aug 2010, Ruslan Nikolaev wrote:
> Yes, I tried this but it does not seem to work. BTW in paravirtualized mode it works fine, the problem is only with HVM.
> 
> I tried to specify root=/dev/xvda (my disk image has no partitions, entire disk image is a single file system).
> 

If your disk file represents a single partition and in your pv config file you
have a disk entry like this one:

disk = [ 'file:/home/ruslan/fs1.img,xvda1,w' ]

then your disk is not going to work in HVM mode.
Qemu must be able to handle your disk otherwise the bootloader won't be
able to boot your kernel.


> My config is (I also tried to comment out device model but it does not help):
> 
> import os, re
> arch = os.uname()[4]
> if re.search('64', arch):
>     arch_libdir = 'lib64'
> else:
>     arch_libdir = 'lib'
> 

remove this part if you are using xl

> kernel = "/usr/lib/xen/boot/hvmloader"
> 
> builder='hvm'
> 
> vcpus=1
> 
> memory = 1024
> shadow_memory = 8
> name = "xenhvm1"
> disk = [ 'file:/home/ruslan/fs1.img,xvda,w' ]

Even though xvda is currently supported it would be better to specify
hda here if you only have one disk, because you need at least an IDE
interface to boot.

> device_model = '/usr/' + arch_libdir + '/xen/bin/qemu-dm'

device_model='qemu-dm' especially if you are using xl

Re: HVM hypercalls

[veeruyours]

Hi,

I recently started working on XEN, and I am looking for ways to invoke
hypercalls from HVM.
I followed your instructions and succeeded in reading MSR register.
But when i attempt to write the physical address of a 4K page from my HVM
guest (2.6.30 kernel), i observed the XEN hypervisor reporting it as bad
GMFN as follows.

[root@f13 ~]# xm dmesg -c
(XEN) traps.c:664:d17 Bad GMFN ffff88001e925 (MFN ffffffffffffffff) to MSR
40000000

Could you please help me in understanding what went wrong in my
implementation.

I am running XEN 4.0.1 on AMD 64bit machine with svm support and the dom0
kernel running 2.6.32.39.

The 
Thanks & Regards,
VSR.


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Re: Re: HVM hypercalls

[Ian Campbell]

On Mon, 2011-05-23 at 08:48 +0100, veeruyours wrote:
> Hi,
> 
> I recently started working on XEN, and I am looking for ways to invoke
> hypercalls from HVM.
> I followed your instructions and succeeded in reading MSR register.
> But when i attempt to write the physical address of a 4K page from my HVM
> guest (2.6.30 kernel), i observed the XEN hypervisor reporting it as bad
> GMFN as follows.
> 
> [root@f13 ~]# xm dmesg -c
> (XEN) traps.c:664:d17 Bad GMFN ffff88001e925 (MFN ffffffffffffffff) to MSR
> 40000000

That supposed GMFN (fff88001e925) looks an awful lot like a virtual
address and not a physical one to me, unless your guest really has >4TB
of RAM assigned...

> 
> Could you please help me in understanding what went wrong in my
> implementation.
> 
> I am running XEN 4.0.1 on AMD 64bit machine with svm support and the dom0
> kernel running 2.6.32.39.
> 
> The 
> Thanks & Regards,
> VSR.
> 
> 
> --
> View this message in context: http://xen.1045712.n5.nabble.com/HVM-hypercalls-tp2541346p4418332.html
> Sent from the Xen - Dev mailing list archive at Nabble.com.
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

Re: Re: HVM hypercalls

[veerasena reddy]

[-- Attachment #1.1: Type: text/plain, Size: 3450 bytes --]

Hi,

Thanks a lot for quick reply.

I modified my code to get physical page address and now i do not see error
message on XEN hypervisor.
Could you please correct if am writing proper physical address or not?

We can write the page address to hypervisor using wrmsr() but who should set
hypercall_page which is declared as extern in hypercall.h on HVM? Because
when i try to invoke HYPERCALL_xxxx(), it reported hypercall_page not
declared. Do we need to enable CONFIG_XEN in HVM kernel in order to invoke
hypercalls to hypervisor?

Could you please share any sample code if you have to get a clear
understanding of HVM hypercalls.

{
        char id[13];
        unsigned int msr1;
        unsigned long  my_hpage_phys;
        int my_hpage_lo, my_hpage_hi;

        __asm__ __volatile__(
                "cpuid"
                : "=b" (*(int *)(&id[0])),
                  "=d" (*(int *)(&id[8])),
                  "=c" (*(int *)(&id[4]))
                : "a" (0x40000000)
        );
        id[12]='\0';
        printk("CPU ID read- %s\n", id);

        /* Read MSR register */
        __asm__ __volatile__(
                "cpuid"
                : "=b" (*(int *)(&msr1))
                : "a" (0x40000002)
        );

        my_hpage_phys = __get_free_page(GFP_ATOMIC);
        hypercall_page = virt_to_phys(my_hpage_phys);
        printk("my_hpage_phys get_free = %lx\n", my_hpage_phys);
        printk("hypercal_page = %p\n", hypercall_page);

        my_hpage_lo = (unsigned long)hypercall_page & 0xffffffff;
        my_hpage_hi = (unsigned long)hypercall_page >> 32;
        printk("my_hpage lo = %x hi = %x\n", my_hpage_lo, my_hpage_hi);
        /* Write hypercall page address to MSR */
        wrmsr(msr1, my_hpage_lo, my_hpage_hi);

        return 0;
}

================= output on HVM ==========
[root@localhost src]# dmesg
my_hypercall_page @ ffffffffa0388000
CPU ID read- XenVMMXenVMM
my_hpage_phys get_free = ffff880005c0b000
hypercal_page = 0000000005c0b000
my_hpage lo = 5c0b000 hi = 0
============================

Thanks & Regards,
VSR.

On Mon, May 23, 2011 at 1:52 PM, Ian Campbell <Ian.Campbell@citrix.com>wrote:

> On Mon, 2011-05-23 at 08:48 +0100, veeruyours wrote:
> > Hi,
> >
> > I recently started working on XEN, and I am looking for ways to invoke
> > hypercalls from HVM.
> > I followed your instructions and succeeded in reading MSR register.
> > But when i attempt to write the physical address of a 4K page from my HVM
> > guest (2.6.30 kernel), i observed the XEN hypervisor reporting it as bad
> > GMFN as follows.
> >
> > [root@f13 ~]# xm dmesg -c
> > (XEN) traps.c:664:d17 Bad GMFN ffff88001e925 (MFN ffffffffffffffff) to
> MSR
> > 40000000
>
> That supposed GMFN (fff88001e925) looks an awful lot like a virtual
> address and not a physical one to me, unless your guest really has >4TB
> of RAM assigned...
>
> >
> > Could you please help me in understanding what went wrong in my
> > implementation.
> >
> > I am running XEN 4.0.1 on AMD 64bit machine with svm support and the dom0
> > kernel running 2.6.32.39.
> >
> > The
> > Thanks & Regards,
> > VSR.
> >
> >
> > --
> > View this message in context:
> http://xen.1045712.n5.nabble.com/HVM-hypercalls-tp2541346p4418332.html
> > Sent from the Xen - Dev mailing list archive at Nabble.com.
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel
>
>
>

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Re: Re: HVM hypercalls

[Ian Campbell]

On Mon, 2011-05-23 at 14:52 +0100, veerasena reddy wrote:
> Hi,
> 
> Thanks a lot for quick reply. 
> 
> I modified my code to get physical page address and now i do not see
> error message on XEN hypervisor.
> Could you please correct if am writing proper physical address or not?
> 
> We can write the page address to hypervisor using wrmsr() but who
> should set hypercall_page which is declared as extern in hypercall.h
> on HVM? Because when i try to invoke HYPERCALL_xxxx(), it reported
> hypercall_page not declared. Do we need to enable CONFIG_XEN in HVM
> kernel in order to invoke hypercalls to hypervisor?

Which kernel are you running with?

This should all be taken care of for you in a kernel with PVHVM support
enabled.

> Could you please share any sample code if you have to get a clear
> understanding of HVM hypercalls.
> 
> {
>         char id[13];
>         unsigned int msr1;
>         unsigned long  my_hpage_phys;
>         int my_hpage_lo, my_hpage_hi;
> 
>         __asm__ __volatile__(
>                 "cpuid"
>                 : "=b" (*(int *)(&id[0])),
>                   "=d" (*(int *)(&id[8])),
>                   "=c" (*(int *)(&id[4]))
>                 : "a" (0x40000000)
>         );
>         id[12]='\0';
>         printk("CPU ID read- %s\n", id);
> 
>         /* Read MSR register */
>         __asm__ __volatile__(
>                 "cpuid"
>                 : "=b" (*(int *)(&msr1))
>                 : "a" (0x40000002)
>         );
> 
>         my_hpage_phys = __get_free_page(GFP_ATOMIC);
>         hypercall_page = virt_to_phys(my_hpage_phys);
>         printk("my_hpage_phys get_free = %lx\n", my_hpage_phys);
>         printk("hypercal_page = %p\n", hypercall_page);
> 
>         my_hpage_lo = (unsigned long)hypercall_page & 0xffffffff;
>         my_hpage_hi = (unsigned long)hypercall_page >> 32;
>         printk("my_hpage lo = %x hi = %x\n", my_hpage_lo,
> my_hpage_hi);
>         /* Write hypercall page address to MSR */
>         wrmsr(msr1, my_hpage_lo, my_hpage_hi);
> 
>         return 0;
> }
> 
> ================= output on HVM ==========
> [root@localhost src]# dmesg
> my_hypercall_page @ ffffffffa0388000
> CPU ID read- XenVMMXenVMM
> my_hpage_phys get_free = ffff880005c0b000
> hypercal_page = 0000000005c0b000
> my_hpage lo = 5c0b000 hi = 0
> ============================
> 
> Thanks & Regards,
> VSR.
> 
> On Mon, May 23, 2011 at 1:52 PM, Ian Campbell
> <Ian.Campbell@citrix.com> wrote:
>         On Mon, 2011-05-23 at 08:48 +0100, veeruyours wrote:
>         > Hi,
>         >
>         > I recently started working on XEN, and I am looking for ways
>         to invoke
>         > hypercalls from HVM.
>         > I followed your instructions and succeeded in reading MSR
>         register.
>         > But when i attempt to write the physical address of a 4K
>         page from my HVM
>         > guest (2.6.30 kernel), i observed the XEN hypervisor
>         reporting it as bad
>         > GMFN as follows.
>         >
>         > [root@f13 ~]# xm dmesg -c
>         > (XEN) traps.c:664:d17 Bad GMFN ffff88001e925 (MFN
>         ffffffffffffffff) to MSR
>         > 40000000
>         
>         
>         That supposed GMFN (fff88001e925) looks an awful lot like a
>         virtual
>         address and not a physical one to me, unless your guest really
>         has >4TB
>         of RAM assigned...
>         
>         
>         >
>         > Could you please help me in understanding what went wrong in
>         my
>         > implementation.
>         >
>         > I am running XEN 4.0.1 on AMD 64bit machine with svm support
>         and the dom0
>         > kernel running 2.6.32.39.
>         >
>         > The
>         > Thanks & Regards,
>         > VSR.
>         >
>         >
>         > --
>         > View this message in context:
>         http://xen.1045712.n5.nabble.com/HVM-hypercalls-tp2541346p4418332.html
>         > Sent from the Xen - Dev mailing list archive at Nabble.com.
>         >
>         > _______________________________________________
>         > Xen-devel mailing list
>         > Xen-devel@lists.xensource.com
>         > http://lists.xensource.com/xen-devel
>         
>         
>         
> 

Re: HVM hypercalls

[veeruyours]

[-- Attachment #1.1: Type: text/plain, Size: 6157 bytes --]

I am running 2.6.30 (downloaded from kernel.org) on top of CENTOS 5.4.
Do u mean i should enable following option

--> Processor type and features
      [*] Paravirtualized guest support  --->
             --> [ ]   Xen guest support (NEW)

But enabling this also selects PARAVIRT and does it make my guest PV guest
or PVHVM guest?

--- Paravirtualized guest support
[*]   Xen guest support
(32)    Maximum allowed size of a domain in gigabytes (NEW)
[ ]     Enable Xen debug and tuning parameters in debugfs
[ ]   KVM paravirtualized clock (NEW)
[ ]   KVM Guest support (NEW)
-*-   Enable paravirtualization code
[ ]     Paravirtualization layer for spinlocks

Could you please suggest how to enable only PVHVM support? I am fine for
moving to recent kernels if required.

Thanks & Regards,
VSR.

On Tue, May 24, 2011 at 5:38 PM, Ian Campbell-12 [via Xen] <
ml-node+4421864-1644938153-207502@n5.nabble.com> wrote:

> On Mon, 2011-05-23 at 14:52 +0100, veerasena reddy wrote:
>
> > Hi,
> >
> > Thanks a lot for quick reply.
> >
> > I modified my code to get physical page address and now i do not see
> > error message on XEN hypervisor.
> > Could you please correct if am writing proper physical address or not?
> >
> > We can write the page address to hypervisor using wrmsr() but who
> > should set hypercall_page which is declared as extern in hypercall.h
> > on HVM? Because when i try to invoke HYPERCALL_xxxx(), it reported
> > hypercall_page not declared. Do we need to enable CONFIG_XEN in HVM
> > kernel in order to invoke hypercalls to hypervisor?
>
> Which kernel are you running with?
>
> This should all be taken care of for you in a kernel with PVHVM support
> enabled.
>
> > Could you please share any sample code if you have to get a clear
> > understanding of HVM hypercalls.
> >
> > {
> >         char id[13];
> >         unsigned int msr1;
> >         unsigned long  my_hpage_phys;
> >         int my_hpage_lo, my_hpage_hi;
> >
> >         __asm__ __volatile__(
> >                 "cpuid"
> >                 : "=b" (*(int *)(&id[0])),
> >                   "=d" (*(int *)(&id[8])),
> >                   "=c" (*(int *)(&id[4]))
> >                 : "a" (0x40000000)
> >         );
> >         id[12]='\0';
> >         printk("CPU ID read- %s\n", id);
> >
> >         /* Read MSR register */
> >         __asm__ __volatile__(
> >                 "cpuid"
> >                 : "=b" (*(int *)(&msr1))
> >                 : "a" (0x40000002)
> >         );
> >
> >         my_hpage_phys = __get_free_page(GFP_ATOMIC);
> >         hypercall_page = virt_to_phys(my_hpage_phys);
> >         printk("my_hpage_phys get_free = %lx\n", my_hpage_phys);
> >         printk("hypercal_page = %p\n", hypercall_page);
> >
> >         my_hpage_lo = (unsigned long)hypercall_page & 0xffffffff;
> >         my_hpage_hi = (unsigned long)hypercall_page >> 32;
> >         printk("my_hpage lo = %x hi = %x\n", my_hpage_lo,
> > my_hpage_hi);
> >         /* Write hypercall page address to MSR */
> >         wrmsr(msr1, my_hpage_lo, my_hpage_hi);
> >
> >         return 0;
> > }
> >
> > ================= output on HVM ==========
> > [root@localhost src]# dmesg
> > my_hypercall_page @ ffffffffa0388000
> > CPU ID read- XenVMMXenVMM
> > my_hpage_phys get_free = ffff880005c0b000
> > hypercal_page = 0000000005c0b000
> > my_hpage lo = 5c0b000 hi = 0
> > ============================
> >
> > Thanks & Regards,
> > VSR.
> >
> > On Mon, May 23, 2011 at 1:52 PM, Ian Campbell
> > <[hidden email] <http://user/SendEmail.jtp?type=node&node=4421864&i=0>>
> wrote:
> >         On Mon, 2011-05-23 at 08:48 +0100, veeruyours wrote:
> >         > Hi,
> >         >
> >         > I recently started working on XEN, and I am looking for ways
> >         to invoke
> >         > hypercalls from HVM.
> >         > I followed your instructions and succeeded in reading MSR
> >         register.
> >         > But when i attempt to write the physical address of a 4K
> >         page from my HVM
> >         > guest (2.6.30 kernel), i observed the XEN hypervisor
> >         reporting it as bad
> >         > GMFN as follows.
> >         >
> >         > [root@f13 ~]# xm dmesg -c
> >         > (XEN) traps.c:664:d17 Bad GMFN ffff88001e925 (MFN
> >         ffffffffffffffff) to MSR
> >         > 40000000
> >
> >
> >         That supposed GMFN (fff88001e925) looks an awful lot like a
> >         virtual
> >         address and not a physical one to me, unless your guest really
> >         has >4TB
> >         of RAM assigned...
> >
> >
> >         >
> >         > Could you please help me in understanding what went wrong in
> >         my
> >         > implementation.
> >         >
> >         > I am running XEN 4.0.1 on AMD 64bit machine with svm support
> >         and the dom0
> >         > kernel running 2.6.32.39.
> >         >
> >         > The
> >         > Thanks & Regards,
> >         > VSR.
> >         >
> >         >
> >         > --
> >         > View this message in context:
> >
> http://xen.1045712.n5.nabble.com/HVM-hypercalls-tp2541346p4418332.html
> >         > Sent from the Xen - Dev mailing list archive at Nabble.com.
> >         >
> >         > _______________________________________________
> >         > Xen-devel mailing list
> >         > [hidden email]<http://user/SendEmail.jtp?type=node&node=4421864&i=1>
> >         > http://lists.xensource.com/xen-devel
> >
> >
> >
> >
>
>
>
> _______________________________________________
> Xen-devel mailing list
> [hidden email] <http://user/SendEmail.jtp?type=node&node=4421864&i=2>
> http://lists.xensource.com/xen-devel
>
>
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>
>


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Re: Re: HVM hypercalls

[Ian Campbell]

On Tue, 2011-05-24 at 14:58 +0100, veeruyours wrote:
> I am running 2.6.30 (downloaded from kernel.org) on top of CENTOS 5.4.

That is a very old kernel (June 2009 IIRC).

> Do u mean i should enable following option 
> 
> --> Processor type and features
>       [*] Paravirtualized guest support  --->
>              --> [ ]   Xen guest support (NEW)
> 
> But enabling this also selects PARAVIRT and does it make my guest PV
> guest or PVHVM guest?

This kernel only support PV and not PVHVM. You need something newer for
PVHVM, I forget exactly when it was but 2.6.38/39 is certainly new
enough.

Ian.

Re: HVM hypercalls

[veeruyours]

[-- Attachment #1.1: Type: text/plain, Size: 2305 bytes --]

Hi,

I downloaded 2.6.38.7 and seen the CONFIG_XEN_PVHVM available. This feature
is automatically selected if XEN and X86_LOCAL_APIC are seletected.

config XEN_PVHVM
        def_bool y
        depends on XEN
        depends on X86_LOCAL_APIC

But, when i select XEN (CONFIG_XEN), it automatically selects "PARAVIRT".
Does that make my HVM guest into PV guest?

CONFIG_PARAVIRT:


This changes the kernel so it can modify itself when it is run
under a hypervisor, potentially improving performance significantly
over full virtualization.  However, when run without a hypervisor the kernel
is theoretically slower and slightly larger.

i do not want to convert HVM guest into PV, i just want to make hypercalls
from HVM guest to hypervisor.

Could you please suggest.

Thanks & Regards,
VSR.

On Tue, May 24, 2011 at 7:39 PM, Ian Campbell-10 [via Xen] <
ml-node+4422155-436573608-207502@n5.nabble.com> wrote:

> On Tue, 2011-05-24 at 14:58 +0100, veeruyours wrote:
> > I am running 2.6.30 (downloaded from kernel.org) on top of CENTOS 5.4.
>
> That is a very old kernel (June 2009 IIRC).
>
> > Do u mean i should enable following option
> >
> > --> Processor type and features
> >       [*] Paravirtualized guest support  --->
> >              --> [ ]   Xen guest support (NEW)
> >
> > But enabling this also selects PARAVIRT and does it make my guest PV
> > guest or PVHVM guest?
>
> This kernel only support PV and not PVHVM. You need something newer for
> PVHVM, I forget exactly when it was but 2.6.38/39 is certainly new
> enough.
>
> Ian.
>
>
> _______________________________________________
> Xen-devel mailing list
> [hidden email] <http://user/SendEmail.jtp?type=node&node=4422155&i=0>
> http://lists.xensource.com/xen-devel
>
>
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>
>


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Re: Re: HVM hypercalls

[Ian Campbell]

On Wed, 2011-05-25 at 08:38 +0100, veeruyours wrote:
> Hi,
> 
> I downloaded 2.6.38.7 and seen the CONFIG_XEN_PVHVM available. This
> feature is automatically selected if XEN and X86_LOCAL_APIC are
> seletected.
> 
> config XEN_PVHVM
>         def_bool y
>         depends on XEN
>         depends on X86_LOCAL_APIC
> 
> But, when i select XEN (CONFIG_XEN), it automatically selects
> "PARAVIRT". Does that make my HVM guest into PV guest?

No. It makes your kernel capable of being used as either PV, PVHVM or
just HVM kernel. The guest type is purely derived from the guest cfg
file you use.

PV vs PVHVM/HVM is controlled by specifying hvm=0|1. PVHVM vs HVM is
controlled via the xen_platform_device=0|1 option, disabling the
platform device (it is enabled by default) puts you back to just HVM
mode.

BTW, this sort of question really belongs on xen-users.

Ian.

> 
> CONFIG_PARAVIRT:                                                                                                                       
> 
> This changes the kernel so it can modify itself when it is run 
> under a hypervisor, potentially improving performance significantly 
> over full virtualization.  However, when run without a hypervisor the
> kernel is theoretically slower and slightly larger.
> 
> i do not want to convert HVM guest into PV, i just want to make
> hypercalls from HVM guest to hypervisor.
> 
> Could you please suggest.
> 
> Thanks & Regards,
> VSR.
> 
> On Tue, May 24, 2011 at 7:39 PM, Ian Campbell-10 [via Xen] <[hidden
> email]> wrote:
>         On Tue, 2011-05-24 at 14:58 +0100, veeruyours wrote: 
>         
>         > I am running 2.6.30 (downloaded from kernel.org) on top of
>         CENTOS 5.4. 
>         
>         
>         That is a very old kernel (June 2009 IIRC). 
>         
>         
>         > Do u mean i should enable following option 
>         > 
>         > --> Processor type and features 
>         >       [*] Paravirtualized guest support  ---> 
>         >              --> [ ]   Xen guest support (NEW) 
>         > 
>         > But enabling this also selects PARAVIRT and does it make my
>         guest PV 
>         > guest or PVHVM guest? 
>         
>         
>         This kernel only support PV and not PVHVM. You need something
>         newer for 
>         PVHVM, I forget exactly when it was but 2.6.38/39 is certainly
>         new 
>         enough. 
>         
>         Ian. 
>         
>         
>         
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