[BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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Hi，
    I got xen source code from  http://www.xen.org/download/index_4.1.2.html
 .
    when using `xl restore`，xc_evtchn_alloc_unbound will raise this error: xc:
error: do_evtchn_op: HYPERVISOR_event_channel_op failed: -1 (3 = No such
process): Internal error.
  what does this mean and what does such process refer to?
    Looking forward to your reply.
    Thanks.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Wed, Dec 26, 2012 at 6:03 PM, 马磊 <aware.why@gmail.com> wrote:

> Hi，
>     I got xen source code from
> http://www.xen.org/download/index_4.1.2.html .
>     when using `xl restore`，xc_evtchn_alloc_unbound will raise this error: xc:
> error: do_evtchn_op: HYPERVISOR_event_channel_op failed: -1 (3 = No such
> process): Internal error.
>   what does this mean and what does such process refer to?
>     Looking forward to your reply.
>     Thanks.
>

The error exactly occurs at  this point: (tools/libxl/libxl_dom.c)
67-int libxl__build_pre(libxl_ctx *ctx, uint32_t domid,



 68              libxl_domain_build_info *info, libxl_domain_build_state
*state)


 69{



 70    xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus);



 71    xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb +
LIBXL_MAXMEM_CONSTANT);


 72    xc_domain_set_memmap_limit(ctx->xch, domid,



 73            (info->hvm) ? info->max_memkb :



 74            (info->max_memkb + info->u.pv.slack_memkb));



 75    xc_domain_set_tsc_info(ctx->xch, domid, info->tsc_mode, 0, 0, 0);



 76    if ( info->disable_migrate )



 77        xc_domain_disable_migrate(ctx->xch, domid);



 78



 79    if (info->hvm) {



 80        unsigned long shadow;



 81        shadow = (info->shadow_memkb + 1023) / 1024;



 82        xc_shadow_control(ctx->xch, domid,
XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION, NULL, 0, &shadow, 0, NULL);


 83    }



 84



 85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);



 86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);



 87    return 0;



 88}

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Wei Liu]

On Wed, Dec 26, 2012 at 10:19:36AM +0000, 马磊 wrote:
> 
> 
> On Wed, Dec 26, 2012 at 6:03 PM, 马磊 <aware.why@gmail.com<mailto:aware.why@gmail.com>> wrote:
> Hi，
>     I got xen source code from  http://www.xen.org/download/index_4.1.2.html .
>     when using `xl restore`，xc_evtchn_alloc_unbound will raise this error: xc: error: do_evtchn_op: HYPERVISOR_event_channel_op failed: -1 (3 = No such process): Internal error.
>   what does this mean and what does such process refer to?
>     Looking forward to your reply.
>     Thanks.
> 
> The error exactly occurs at  this point: (tools/libxl/libxl_dom.c)
> 67-int libxl__build_pre(libxl_ctx *ctx, uint32_t domid,
>  68              libxl_domain_build_info *info, libxl_domain_build_state *state)
>  69{
>  70    xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus);
>  71    xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + LIBXL_MAXMEM_CONSTANT);
>  72    xc_domain_set_memmap_limit(ctx->xch, domid,
>  73            (info->hvm) ? info->max_memkb :
>  74            (info->max_memkb + info->u.pv.slack_memkb));
>  75    xc_domain_set_tsc_info(ctx->xch, domid, info->tsc_mode, 0, 0, 0);
>  76    if ( info->disable_migrate )
>  77        xc_domain_disable_migrate(ctx->xch, domid);
>  78
>  79    if (info->hvm) {
>  80        unsigned long shadow;
>  81        shadow = (info->shadow_memkb + 1023) / 1024;
>  82        xc_shadow_control(ctx->xch, domid, XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION, NULL, 0, &shadow, 0, NULL);
>  83    }
>  84
>  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
>  86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
>  87    return 0;
>  88}

I played with save/restore several days ago but I never saw this error.

The relavent code in Xen is in
xen/common/event_channel.c:do_event_channel_op


Wei.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Wed, Dec 26, 2012 at 9:41 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:

> On Wed, Dec 26, 2012 at 10:19:36AM +0000, 马磊 wrote:
> >
> >
> > On Wed, Dec 26, 2012 at 6:03 PM, 马磊 <aware.why@gmail.com<mailto:
> aware.why@gmail.com>> wrote:
> > Hi，
> >     I got xen source code from
> http://www.xen.org/download/index_4.1.2.html .
> >     when using `xl restore`，xc_evtchn_alloc_unbound will raise this
> error: xc: error: do_evtchn_op: HYPERVISOR_event_channel_op failed: -1 (3 =
> No such process): Internal error.
> >   what does this mean and what does such process refer to?
> >     Looking forward to your reply.
> >     Thanks.
> >
> > The error exactly occurs at  this point: (tools/libxl/libxl_dom.c)
> > 67-int libxl__build_pre(libxl_ctx *ctx, uint32_t domid,
> >  68              libxl_domain_build_info *info, libxl_domain_build_state
> *state)
> >  69{
> >  70    xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus);
> >  71    xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb +
> LIBXL_MAXMEM_CONSTANT);
> >  72    xc_domain_set_memmap_limit(ctx->xch, domid,
> >  73            (info->hvm) ? info->max_memkb :
> >  74            (info->max_memkb + info->u.pv.slack_memkb));
> >  75    xc_domain_set_tsc_info(ctx->xch, domid, info->tsc_mode, 0, 0, 0);
> >  76    if ( info->disable_migrate )
> >  77        xc_domain_disable_migrate(ctx->xch, domid);
> >  78
> >  79    if (info->hvm) {
> >  80        unsigned long shadow;
> >  81        shadow = (info->shadow_memkb + 1023) / 1024;
> >  82        xc_shadow_control(ctx->xch, domid,
> XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION, NULL, 0, &shadow, 0, NULL);
> >  83    }
> >  84
> >  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
> >  86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
> >  87    return 0;
> >  88}
>
> I played with save/restore several days ago but I never saw this error.
>
> The relavent code in Xen is in
> xen/common/event_channel.c:do_event_channel_op
>
>
> Wei.
>
I said `xl restore`, not `xm restore`, and the relevant code is in
src/tools/libxl.
It seems that yours aren't the same version as mine

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Wei Liu]

On Wed, Dec 26, 2012 at 02:45:46PM +0000, 马磊 wrote:
> I said `xl restore`, not `xm restore`, and the relevant code is in src/tools/libxl.
> It seems that yours aren't the same version as mine

I didn't say xm restore either. I was referring to the generic
save/restore functionality, though in fact I did use xl. And the
function I told you is in Xen hypervisor source code, not part of any
tool stack.

Whichever tools stack you use, it will eventually issue hypercall to Xen
via libxc. I don't use the same version as yours since I always plays
with xen staging unstable. However I don't think allocation code
has potential difference between 4.1.2 and staging unstable.


Wei.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Thu, Dec 27, 2012 at 3:33 AM, Wei Liu <Wei.Liu2@citrix.com> wrote:

> On Wed, Dec 26, 2012 at 02:45:46PM +0000, 马磊 wrote:
> > I said `xl restore`, not `xm restore`, and the relevant code is in
> src/tools/libxl.
> > It seems that yours aren't the same version as mine
>
> I didn't say xm restore either. I was referring to the generic
> save/restore functionality, though in fact I did use xl. And the
> function I told you is in Xen hypervisor source code, not part of any
> tool stack.
>
> Whichever tools stack you use, it will eventually issue hypercall to Xen
> via libxc. I don't use the same version as yours since I always plays
> with xen staging unstable. However I don't think allocation code
> has potential difference between 4.1.2 and staging unstable.
>
>
> Wei.
>
I got it, but the error `  xc: error: do_evtchn_op:
HYPERVISOR_event_channel_op failed: -1 (3 = No such process): Internal
error. ` said no such process, the system error description
didn't seem has anything to do with the following lines wich raised
 85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
 86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Wei Liu]

On Thu, 2012-12-27 at 02:12 +0000, 马磊 wrote:
>         
> I got it, but the error `  xc: error: do_evtchn_op:
> HYPERVISOR_event_channel_op failed: -1 (3 = No such process): Internal
> error. ` said no such process, the system error description
> didn't seem has anything to do with the following lines wich raised 
>  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid,
> 0);
>  86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid,
> 0);

The error code -1 is -EPERM, which means you don't have permission to
issue this operation. I don't think this is a bug. There might be some
problems with your setup.

If you need any pointer in reading source code, I will be happy to help.


Wei.


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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Thu, Dec 27, 2012 at 8:41 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:

> On Thu, 2012-12-27 at 02:12 +0000, 马磊 wrote:
> >
> > I got it, but the error `  xc: error: do_evtchn_op:
> > HYPERVISOR_event_channel_op failed: -1 (3 = No such process): Internal
> > error. ` said no such process, the system error description
> > didn't seem has anything to do with the following lines wich raised
> >  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid,
> > 0);
> >  86    state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid,
> > 0);
>
> The error code -1 is -EPERM, which means you don't have permission to
> issue this operation. I don't think this is a bug. There might be some
> problems with your setup.
>
> If you need any pointer in reading source code, I will be happy to help.
>
>
> Wei.
>
>     Thanks for your kindness!

    I looked into the functions for logging, in this case,  `3 = No such
process` was from `errno` and the ` HYPERVISOR_event_channel_op failed: -1 `
was from hypervisor-level error(src/xen/common/event_channel.c).
In my option, that's to say, error number of -1 was caused by hypervisor;
but what was the error number of 3 caused by,  dom0?
Do both the two error numbers refer to the description defined in errno.h
or else hypervisor has its own error description?

    I run `xl restore` in sudo mode, it had no reason for `EPERM`.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Wei Liu]

On Fri, 2012-12-28 at 03:13 +0000, 马磊 wrote:
> 
> 
> On Thu, Dec 27, 2012 at 8:41 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:
>         On Thu, 2012-12-27 at 02:12 +0000, 马磊 wrote:
>         >
>         > I got it, but the error `  xc: error: do_evtchn_op:
>         > HYPERVISOR_event_channel_op failed: -1 (3 = No such
>         process): Internal
>         > error. ` said no such process, the system error description
>         > didn't seem has anything to do with the following lines wich
>         raised
>         >  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch,
>         domid,
>         > 0);
>         >  86    state->console_port =
>         xc_evtchn_alloc_unbound(ctx->xch, domid,
>         > 0);
>         
>         
>         The error code -1 is -EPERM, which means you don't have
>         permission to
>         issue this operation. I don't think this is a bug. There might
>         be some
>         problems with your setup.
>         
>         If you need any pointer in reading source code, I will be
>         happy to help.
>         
>         
>         Wei.
>         
>     Thanks for your kindness! 
> 
> 
>     I looked into the functions for logging, in this case,  `3 = No
> such process` was from `errno` and the ` HYPERVISOR_event_channel_op
> failed: -1 ` was from hypervisor-level
> error(src/xen/common/event_channel.c).
> In my option, that's to say, error number of -1 was caused by
> hypervisor; but what was the error number of 3 caused by,  dom0?
> Do both the two error numbers refer to the description defined in
> errno.h or else hypervisor has its own error description?
> 

I think the two files are mostly the same, but to be sure you need to
look into the source file in both Linux and Xen. You should start from
the hypervisor level, find out why it returns -EPERM. Root user in Dom0
has nothing to do with privilege in hypervisor level.


Wei.


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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Fri, Dec 28, 2012 at 6:46 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:

> On Fri, 2012-12-28 at 03:13 +0000, 马磊 wrote:
> >
> >
> > On Thu, Dec 27, 2012 at 8:41 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:
> >         On Thu, 2012-12-27 at 02:12 +0000, 马磊 wrote:
> >         >
> >         > I got it, but the error `  xc: error: do_evtchn_op:
> >         > HYPERVISOR_event_channel_op failed: -1 (3 = No such
> >         process): Internal
> >         > error. ` said no such process, the system error description
> >         > didn't seem has anything to do with the following lines wich
> >         raised
> >         >  85    state->store_port = xc_evtchn_alloc_unbound(ctx->xch,
> >         domid,
> >         > 0);
> >         >  86    state->console_port =
> >         xc_evtchn_alloc_unbound(ctx->xch, domid,
> >         > 0);
> >
> >
> >         The error code -1 is -EPERM, which means you don't have
> >         permission to
> >         issue this operation. I don't think this is a bug. There might
> >         be some
> >         problems with your setup.
> >
> >         If you need any pointer in reading source code, I will be
> >         happy to help.
> >
> >
> >         Wei.
> >
> >     Thanks for your kindness!
> >
> >
> >     I looked into the functions for logging, in this case,  `3 = No
> > such process` was from `errno` and the ` HYPERVISOR_event_channel_op
> > failed: -1 ` was from hypervisor-level
> > error(src/xen/common/event_channel.c).
> > In my option, that's to say, error number of -1 was caused by
> > hypervisor; but what was the error number of 3 caused by,  dom0?
> > Do both the two error numbers refer to the description defined in
> > errno.h or else hypervisor has its own error description?
> >
>
> I think the two files are mostly the same, but to be sure you need to
> look into the source file in both Linux and Xen. You should start from
> the hypervisor level, find out why it returns -EPERM. Root user in Dom0
> has nothing to do with privilege in hypervisor level.
>
>
> Wei.
>
> The scene is that there are more than 10 processes, each process calls `xl
restore` to start a VM where a virus sample will run to detect the sample's
behaviour  about every 120 seconds.
For a long time, such as 5 days or 15 days, the xen server where the
processes run will raise this error with a certain probability.
Maybe it has something to do with the hypervisor's stability.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Wei Liu]

On Mon, 2012-12-31 at 03:10 +0000, 马磊 wrote:
>         
>         
>         
>         I think the two files are mostly the same, but to be sure you
>         need to
>         look into the source file in both Linux and Xen. You should
>         start from
>         the hypervisor level, find out why it returns -EPERM. Root
>         user in Dom0
>         has nothing to do with privilege in hypervisor level.
>         
>         
>         Wei.
>         
> The scene is that there are more than 10 processes, each process calls
> `xl restore` to start a VM where a virus sample will run to detect the
> sample's behaviour  about every 120 seconds.
> For a long time, such as 5 days or 15 days, the xen server where the
> processes run will raise this error with a certain probability.
> Maybe it has something to do with the hypervisor's stability.

This is not a usual scenario. Sorry I don't know how to reproduce this.

But the code path in hypervisor for evtchn_alloc_unbound is quite short,
you may try adding some debug output along the path to see which step
fails then report back.


Wei.


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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Mon, Dec 31, 2012 at 8:03 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:

> On Mon, 2012-12-31 at 03:10 +0000, 马磊 wrote:
> >
> >
> >
> >         I think the two files are mostly the same, but to be sure you
> >         need to
> >         look into the source file in both Linux and Xen. You should
> >         start from
> >         the hypervisor level, find out why it returns -EPERM. Root
> >         user in Dom0
> >         has nothing to do with privilege in hypervisor level.
> >
> >
> >         Wei.
> >
> > The scene is that there are more than 10 processes, each process calls
> > `xl restore` to start a VM where a virus sample will run to detect the
> > sample's behaviour  about every 120 seconds.
> > For a long time, such as 5 days or 15 days, the xen server where the
> > processes run will raise this error with a certain probability.
> > Maybe it has something to do with the hypervisor's stability.
>
> This is not a usual scenario. Sorry I don't know how to reproduce this.
>
> But the code path in hypervisor for evtchn_alloc_unbound is quite short,
> you may try adding some debug output along the path to see which step
> fails then report back.
>
>
> Wei.
>
> BTW, it's needed to tell you my environment background;
I installed centos6.2 and then installed xen rpms from
http://xenbits.xen.org/people/mayoung/EL6.xen/.

At present, I'm not sure what function used to add the debug statement (is
it printk?) and where to look for the debug log info (is it
/var/log/message?)  .

The returned errno is from src/xen/common/event_channel.c
874-long do_event_channel_op(int cmd, XEN_GUEST_HANDLE(void) arg)



 875{



 876    long rc;



 877



 878    switch ( cmd )



 879    {



 880    case EVTCHNOP_alloc_unbound: {



 881        struct evtchn_alloc_unbound alloc_unbound;



 882        if ( copy_from_guest(&alloc_unbound, arg, 1) != 0 )



 883            return -EFAULT;



 884        rc = evtchn_alloc_unbound(&alloc_unbound);         // only here
returns -1(EPERM) ,  others return -EFAULT


 885        if ( (rc == 0) && (copy_to_guest(arg, &alloc_unbound, 1) != 0)
)


 886            rc = -EFAULT; /* Cleaning up here would be a mess! */



 887        break;



 888    }


Two statements below may affect the rc.
124-static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)



 125{



 126    struct evtchn *chn;



 127    struct domain *d;



 128    int            port;



 129    domid_t        dom = alloc->dom;



 130    long           rc;



 131



 132    rc = rcu_lock_target_domain_by_id(dom, &d);



 133    if ( rc )



 134        return rc;



 135



 136    spin_lock(&d->event_lock);



 137



 138    if ( (port = get_free_port(d)) < 0 )



 139        ERROR_EXIT_DOM(port, d);



 140    chn = evtchn_from_port(d, port);



 141



 142    rc = xsm_evtchn_unbound(d, chn, alloc->remote_dom);



 143    if ( rc )



 144        goto out;



 145



 146    chn->state = ECS_UNBOUND;



 147    if ( (chn->u.unbound.remote_domid = alloc->remote_dom) ==
DOMID_SELF )


 148        chn->u.unbound.remote_domid = current->domain->domain_id;
149



 150    alloc->port = port;



 151



 152 out:



 153    spin_unlock(&d->event_lock);



 154    rcu_unlock_domain(d);



 155



 156    return rc;



 157}

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Fri, Jan 4, 2013 at 11:23 AM, 马磊 <aware.why@gmail.com> wrote:

>
>
> On Mon, Dec 31, 2012 at 8:03 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:
>
>> On Mon, 2012-12-31 at 03:10 +0000, 马磊 wrote:
>> >
>> >
>> >
>> >         I think the two files are mostly the same, but to be sure you
>> >         need to
>> >         look into the source file in both Linux and Xen. You should
>> >         start from
>> >         the hypervisor level, find out why it returns -EPERM. Root
>> >         user in Dom0
>> >         has nothing to do with privilege in hypervisor level.
>> >
>> >
>> >         Wei.
>> >
>> > The scene is that there are more than 10 processes, each process calls
>> > `xl restore` to start a VM where a virus sample will run to detect the
>> > sample's behaviour  about every 120 seconds.
>> > For a long time, such as 5 days or 15 days, the xen server where the
>> > processes run will raise this error with a certain probability.
>> > Maybe it has something to do with the hypervisor's stability.
>>
>> This is not a usual scenario. Sorry I don't know how to reproduce this.
>>
>> But the code path in hypervisor for evtchn_alloc_unbound is quite short,
>> you may try adding some debug output along the path to see which step
>> fails then report back.
>>
>>
>> Wei.
>>
>> BTW, it's needed to tell you my environment background;
> I installed centos6.2 and then installed xen rpms from
> http://xenbits.xen.org/people/mayoung/EL6.xen/.
>
> At present, I'm not sure what function used to add the debug statement (is
> it printk?) and where to look for the debug log info (is it
> /var/log/message?)  .
>
> The returned errno is from src/xen/common/event_channel.c
> 874-long do_event_channel_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>
>
>
>  875{
>
>
>
>  876    long rc;
>
>
>
>  877
>
>
>
>  878    switch ( cmd )
>
>
>
>  879    {
>
>
>
>  880    case EVTCHNOP_alloc_unbound: {
>
>
>
>  881        struct evtchn_alloc_unbound alloc_unbound;
>
>
>
>  882        if ( copy_from_guest(&alloc_unbound, arg, 1) != 0 )
>
>
>
>  883            return -EFAULT;
>
>
>
>  884        rc = evtchn_alloc_unbound(&alloc_unbound);         // only
> here returns -1(EPERM) ,  others return -EFAULT
>
>
>  885        if ( (rc == 0) && (copy_to_guest(arg, &alloc_unbound, 1) != 0)
> )
>
>
>  886            rc = -EFAULT; /* Cleaning up here would be a mess! */
>
>
>
>  887        break;
>
>
>
>  888    }
>
>
>
> Two statements below may affect the rc.
> 124-static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
>
>
>
>  125{
>
>
>
>  126    struct evtchn *chn;
>
>
>
>  127    struct domain *d;
>
>
>
>  128    int            port;
>
>
>
>  129    domid_t        dom = alloc->dom;
>
>
>
>  130    long           rc;
>
>
>
>  131
>
>
>
>  132    rc = rcu_lock_target_domain_by_id(dom, &d);
>
>
>
>  133    if ( rc )
>
>
>
>  134        return rc;
>
>
>
>  135
>
>
>
>  136    spin_lock(&d->event_lock);
>
>
>
>  137
>
>
>
>  138    if ( (port = get_free_port(d)) < 0 )
>
>
>
>  139        ERROR_EXIT_DOM(port, d);
>
>
>
>  140    chn = evtchn_from_port(d, port);
>
>
>
>  141
>
>
>
>  142    rc = xsm_evtchn_unbound(d, chn, alloc->remote_dom);
>
>
>
>  143    if ( rc )
>
>
>
>  144        goto out;
>
>
>
>  145
>
>
>
>  146    chn->state = ECS_UNBOUND;
>
>
>
>  147    if ( (chn->u.unbound.remote_domid = alloc->remote_dom) ==
> DOMID_SELF )
>
>
>  148        chn->u.unbound.remote_domid = current->domain->domain_id;
> 149
>
>
>
>  150    alloc->port = port;
>
>
>
>  151
>
>
>
>  152 out:
>
>
>
>  153    spin_unlock(&d->event_lock);
>
>
>
>  154    rcu_unlock_domain(d);
>
>
>
>  155
>
>
>
>  156    return rc;
>
>
>
>  157}
>
>
I looked into it again and found that it was caused probably by
src/xen/common/domain.c:

 421-int rcu_lock_target_domain_by_id(domid_t dom, struct domain **d)



 422{



 423    if ( dom == DOMID_SELF )



 424    {



 425        *d = rcu_lock_current_domain();



 426        return 0;



 427    }



 428



 429    if ( (*d = rcu_lock_domain_by_id(dom)) == NULL )



 430        return -ESRCH;



 431



 432    if ( !IS_PRIV_FOR(current->domain, *d) )



 433    {



 434        rcu_unlock_domain(*d);



 435        return -EPERM;



 436    }



 437



 438    return 0;



 439}


the macro `IS_PRIV_FOR` is defined here src/xen/include/xen/sched.h:

638#define IS_PRIV_FOR(_d, _t) (IS_PRIV(_d) || ((_d)->target &&
(_d)->target == (_t)))

*I couldn't understand that what  IS_PRIV_FOR  means?!*

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Ian Campbell]

On Fri, 2013-01-04 at 06:27 +0000, 马磊 wrote:
> 
> the macro `IS_PRIV_FOR` is defined here src/xen/include/xen/sched.h: 
>         638#define IS_PRIV_FOR(_d, _t) (IS_PRIV(_d) || ((_d)->target
>         && (_d)->target == (_t))) 
>         
>         
> I couldn't understand that what  IS_PRIV_FOR  means?!

It tells you if domains _d has special privileges over the domain _t
(the target). This is typically true of domains which are privileged  in
general (the IS_PRIV check, typically true only for dom0) or of stub
domains for HVM which have their ->target set via XEN_DOMCTL_set_target.

However this is all a red-herring since you are seeing ESRCH and not
EPERM as described in my other mail.

Ian.


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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Fri, Jan 4, 2013 at 5:20 PM, Ian Campbell <Ian.Campbell@citrix.com>wrote:

> On Fri, 2013-01-04 at 06:27 +0000, 马磊 wrote:
> >
> > the macro `IS_PRIV_FOR` is defined here src/xen/include/xen/sched.h:
> >         638#define IS_PRIV_FOR(_d, _t) (IS_PRIV(_d) || ((_d)->target
> >         && (_d)->target == (_t)))
> >
> >
> > I couldn't understand that what  IS_PRIV_FOR  means?!
>
> It tells you if domains _d has special privileges over the domain _t
> (the target). This is typically true of domains which are privileged  in
> general (the IS_PRIV check, typically true only for dom0) or of stub
> domains for HVM which have their ->target set via XEN_DOMCTL_set_target.
>
> However this is all a red-herring since you are seeing ESRCH and not
> EPERM as described in my other mail.
>
> Ian.
>
> What do you mean by that ` However this is all a red-herring since you are
seeing ESRCH and not
EPERM as described in my other mail. ` The src/xen/include/xen/errno.h
 defines:

  4#define EPERM        1  /* Operation not permitted */
  5#define ENOENT       2  /* No such file or directory */
  6#define ESRCH        3  /* No such process */

Besides, the xc error logging reported -1 and 3, *you said -1 only told
there was an error occurring and 3 is the real reason?!*
*Maybe I misunderstood your real meaning.*

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[Ian Campbell]

On Fri, 2013-01-04 at 11:34 +0000, 马磊 wrote:

> you said -1 only told there was an error occurring and 3 is the real
> reason?!

That is correct.

Ian.



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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Fri, Jan 4, 2013 at 7:42 PM, Ian Campbell <Ian.Campbell@citrix.com>wrote:

> On Fri, 2013-01-04 at 11:34 +0000, 马磊 wrote:
>
> > you said -1 only told there was an error occurring and 3 is the real
> > reason?!
>
> That is correct.
>
> Ian.
>
>
> The excution path is like this:
xl_cmdimpl.c:create_domain() -->
libxl_create.c:libxl_domain_create_restore()
-->  libxl_create.c:do_domain_create() -->  libxl_create.c:domain_restore()
--> libxl_create.c:libxl__build_pre() -->
libxc/xc_evtchn.c:xc_evtchn_alloc_unbound()
-->  libxc/xc_evtchn.c:do_evtchn_op() -->
libxc/xc_private.c:do_xen_hypercall()

so far, it raised an error and do_xen_hypercall return -1 and errno set to
be 3.

You mean that 3 which is the real error code is set by ioctl() and   -1 has
no value of reference!
But -1 is the return value of
src/xen/common/event_channel.c:do_event_channel_op(), we can trace it to
find that it was returned by
src/xen/common/domain.c:rcu_lock_target_domain_by_id() and so it failed at
this point.
Why did it fail there, I can't understand that and that blocked me. I'm
greateful to be helped.

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Re: [BUG]: when using `xl restore`，xc_evtchn_alloc_unbound will raise this error

[马磊]

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On Fri, Jan 4, 2013 at 11:23 AM, 马磊 <aware.why@gmail.com> wrote:

>
>
> On Mon, Dec 31, 2012 at 8:03 PM, Wei Liu <Wei.Liu2@citrix.com> wrote:
>
>> On Mon, 2012-12-31 at 03:10 +0000, 马磊 wrote:
>> >
>> >
>> >
>> >         I think the two files are mostly the same, but to be sure you
>> >         need to
>> >         look into the source file in both Linux and Xen. You should
>> >         start from
>> >         the hypervisor level, find out why it returns -EPERM. Root
>> >         user in Dom0
>> >         has nothing to do with privilege in hypervisor level.
>> >
>> >
>> >         Wei.
>> >
>> > The scene is that there are more than 10 processes, each process calls
>> > `xl restore` to start a VM where a virus sample will run to detect the
>> > sample's behaviour  about every 120 seconds.
>> > For a long time, such as 5 days or 15 days, the xen server where the
>> > processes run will raise this error with a certain probability.
>> > Maybe it has something to do with the hypervisor's stability.
>>
>> This is not a usual scenario. Sorry I don't know how to reproduce this.
>>
>> But the code path in hypervisor for evtchn_alloc_unbound is quite short,
>> you may try adding some debug output along the path to see which step
>> fails then report back.
>>
>>
>> Wei.
>>
>> BTW, it's needed to tell you my environment background;
> I installed centos6.2 and then installed xen rpms from
> http://xenbits.xen.org/people/mayoung/EL6.xen/.
>
> At present, I'm not sure what function used to add the debug statement (is
> it printk?) and where to look for the debug log info (is it
> /var/log/message?)  .
>
> The returned errno is from src/xen/common/event_channel.c
> 874-long do_event_channel_op(int cmd, XEN_GUEST_HANDLE(void) arg)
>
>
>
>  875{
>
>
>
>  876    long rc;
>
>
>
>  877
>
>
>
>  878    switch ( cmd )
>
>
>
>  879    {
>
>
>
>  880    case EVTCHNOP_alloc_unbound: {
>
>
>
>  881        struct evtchn_alloc_unbound alloc_unbound;
>
>
>
>  882        if ( copy_from_guest(&alloc_unbound, arg, 1) != 0 )
>
>
>
>  883            return -EFAULT;
>
>
>
>  884        rc = evtchn_alloc_unbound(&alloc_unbound);         // only
> here returns -1(EPERM) ,  others return -EFAULT
>
>
>  885        if ( (rc == 0) && (copy_to_guest(arg, &alloc_unbound, 1) != 0)
> )
>
>
>  886            rc = -EFAULT; /* Cleaning up here would be a mess! */
>
>
>
>  887        break;
>
>
>
>  888    }
>
>
> Two statements below may affect the rc.
> 124-static long evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
>
>
>
>  125{
>
>
>
>  126    struct evtchn *chn;
>
>
>
>  127    struct domain *d;
>
>
>
>  128    int            port;
>
>
>
>  129    domid_t        dom = alloc->dom;
>
>
>
>  130    long           rc;
>
>
>
>  131
>
>
>
>  132    rc = rcu_lock_target_domain_by_id(dom, &d);
>
>
>
>  133    if ( rc )
>
>
>
>  134        return rc;
>
>
>
>  135
>
>
>
>  136    spin_lock(&d->event_lock);
>
>
>
>  137
>
>
>
>  138    if ( (port = get_free_port(d)) < 0 )
>
>
>
>  139        ERROR_EXIT_DOM(port, d);
>
>
>
>  140    chn = evtchn_from_port(d, port);
>
>
>
>  141
>
>
>
>  142    rc = xsm_evtchn_unbound(d, chn, alloc->remote_dom);
>
>
>
>  143    if ( rc )
>
>
>
>  144        goto out;
>
>
>
>  145
>
>
>
>  146    chn->state = ECS_UNBOUND;
>
>
>
>  147    if ( (chn->u.unbound.remote_domid = alloc->remote_dom) ==
> DOMID_SELF )
>
>
>  148        chn->u.unbound.remote_domid = current->domain->domain_id;
> 149
>
>
>
>  150    alloc->port = port;
>
>
>
>  151
>
>
>
>  152 out:
>
>
>
>  153    spin_unlock(&d->event_lock);
>
>
>
>  154    rcu_unlock_domain(d);
>
>
>
>  155
>
>
>
>  156    return rc;
>
>
>
>  157}
>
>
I don't know how to debug the hypervisor...
Could you give me some advice?

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