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Re: [Xen-devel] Xen-unstable-staging: Xen BUG at iommu_map.c:455



On 11/04/15 15:11, Sander Eikelenboom wrote:
> Friday, April 10, 2015, 8:55:27 PM, you wrote:
>
>> On 10/04/15 11:24, Sander Eikelenboom wrote:
>>> Hi Andrew,
>>>
>>> Finally got some time to figure this out .. and i have narrowed it down to:
>>> git://xenbits.xen.org/staging/qemu-upstream-unstable.git
>>> commit 7665d6ba98e20fb05c420de947c1750fd47e5c07 "Xen: Use the ioreq-server 
>>> API when available"
>>> A straight revert of this commit prevents the issue from happening.
>>>
>>> The reason i had a hard time figuring this out was:
>>> - I wasn't aware of this earlier, since git pulling the main xen tree, 
>>> doesn't 
>>>   auto update the qemu-* trees.
>> This has caught me out so many times.  It is very non-obvious behaviour.
>>> - So i happen to get this when i cloned a fresh tree to try to figure out 
>>> the 
>>>   other issue i was seeing.
>>> - After that checking out previous versions of the main xen tree didn't 
>>> resolve 
>>>   this new issue, because the qemu tree doesn't get auto updated and is set 
>>>   "master".
>>> - Cloning a xen-stable-4.5.0 made it go away .. because that has a specific 
>>>   git://xenbits.xen.org/staging/qemu-upstream-unstable.git tag which is not 
>>>   master.
>>>
>>> *sigh* 
>>>
>>> This is tested with xen main tree at last commit 
>>> 3a28f760508fb35c430edac17a9efde5aff6d1d5
>>> (normal xen-unstable, not the staging branch)
>>>
>>> Ok so i have added some extra debug info (see attached diff) and this is 
>>> the 
>>> output when it crashes due to something the commit above triggered, the 
>>> level is out of bounds and the pfn looks fishy too.
>>> Complete serial log from both bad and good (specific commit reverted) are 
>>> attached.
>> Just to confirm, you are positively identifying a qemu changeset as
>> causing this crash?
>> If so, the qemu change has discovered a pre-existing issue in the
>> toolstack pci-passthrough interface.  Whatever qemu is or isn't doing,
>> it should not be able to cause a crash like this.
>> With this in mind, I need to brush up on my AMD-Vi details.
>> In the meantime, can you run with the following patch to identify what
>> is going on, domctl wise?  I assume it is the assign_device which is
>> failing, but it will be nice to observe the differences between the
>> working and failing case, which might offer a hint.
> Hrrm with your patch i end up with a fatal page fault in iommu_do_pci_domctl:
>
> (XEN) [2015-04-11 14:03:31.833] ----[ Xen-4.6-unstable  x86_64  debug=y  
> Tainted:    C ]----
> (XEN) [2015-04-11 14:03:31.857] CPU:    5
> (XEN) [2015-04-11 14:03:31.868] RIP:    e008:[<ffff82d08014c52c>] 
> iommu_do_pci_domctl+0x2dc/0x740
> (XEN) [2015-04-11 14:03:31.894] RFLAGS: 0000000000010256   CONTEXT: hypervisor
> (XEN) [2015-04-11 14:03:31.915] rax: 0000000000000008   rbx: 0000000000000800 
>   rcx: ffffffffffebe5ed
> (XEN) [2015-04-11 14:03:31.942] rdx: 0000000000000800   rsi: 0000000000000000 
>   rdi: ffff830256ef7e38
> (XEN) [2015-04-11 14:03:31.968] rbp: ffff830256ef7c98   rsp: ffff830256ef7c08 
>   r8:  00000000deadbeef
> (XEN) [2015-04-11 14:03:31.995] r9:  00000000deadbeef   r10: ffff82d08024e500 
>   r11: 0000000000000282
> (XEN) [2015-04-11 14:03:32.022] r12: 0000000000000000   r13: 0000000000000008 
>   r14: 0000000000000000
> (XEN) [2015-04-11 14:03:32.049] r15: 0000000000000000   cr0: 0000000080050033 
>   cr4: 00000000000006f0
> (XEN) [2015-04-11 14:03:32.076] cr3: 00000002336a6000   cr2: 0000000000000000
> (XEN) [2015-04-11 14:03:32.096] ds: 0000   es: 0000   fs: 0000   gs: 0000   
> ss: e010   cs: e008
> (XEN) [2015-04-11 14:03:32.121] Xen stack trace from rsp=ffff830256ef7c08:
> (XEN) [2015-04-11 14:03:32.141]    ffff830256ef7c78 ffff82d08012c178 
> ffff830256ef7c28 ffff830256ef7c28
> (XEN) [2015-04-11 14:03:32.168]    0000000000000010 0000000000000000 
> 0000000000000000 0000000000000000
> (XEN) [2015-04-11 14:03:32.195]    00000000000006f0 00007fe300000000 
> ffff830256eb7790 ffff83025cc6d300
> (XEN) [2015-04-11 14:03:32.222]    ffff82d080330c60 00007fe396bab004 
> 0000000000000000 00007fe396bab004
> (XEN) [2015-04-11 14:03:32.249]    0000000000000000 0000000000000005 
> ffff830256ef7ca8 ffff82d08014900b
> (XEN) [2015-04-11 14:03:32.276]    ffff830256ef7d98 ffff82d080161f2d 
> 0000000000000010 0000000000000000
> (XEN) [2015-04-11 14:03:32.303]    0000000000000000 ffff830256ef7ce8 
> ffff82d08018b655 ffff830256ef7d48
> (XEN) [2015-04-11 14:03:32.330]    ffff830256ef7cf8 ffff82d08018b66a 
> ffff830256ef7d38 ffff82d08012925e
> (XEN) [2015-04-11 14:03:32.357]    ffff830256efc068 0000000800000001 
> 800000022e12c167 0000000000000000
> (XEN) [2015-04-11 14:03:32.384]    0000000000000002 ffff830256ef7e38 
> 0000000800000000 800000022e12c167
> (XEN) [2015-04-11 14:03:32.411]    0000000000000003 ffff830256ef7db8 
> 0000000000000000 00007fe396780eb0
> (XEN) [2015-04-11 14:03:32.439]    0000000000000202 ffffffffffffffff 
> 0000000000000000 00007fe396bab004
> (XEN) [2015-04-11 14:03:32.466]    0000000000000000 0000000000000005 
> ffff830256ef7ef8 ffff82d08010497f
> (XEN) [2015-04-11 14:03:32.493]    0000000000000001 0000000000100001 
> 800000022e12c167 ffff88001f7ecc00
> (XEN) [2015-04-11 14:03:32.520]    00007fe396780eb0 ffff88001c849508 
> 0000000e00000007 ffffffff8105594a
> (XEN) [2015-04-11 14:03:32.547]    000000000000e033 0000000000000202 
> ffff88001ece3d40 000000000000e02b
> (XEN) [2015-04-11 14:03:32.574]    ffff830256ef7e28 ffff82d080194933 
> 000000000000beef ffffffff81bd6c85
> (XEN) [2015-04-11 14:03:32.601]    ffff830256ef7f08 ffff82d080193edd 
> 0000000b0000002d 0000000000000001
> (XEN) [2015-04-11 14:03:32.628]    0000000100000800 00007fe3962abbd0 
> ffff000a81050001 00007fe39656ce6e
> (XEN) [2015-04-11 14:03:32.655]    00007ffdf2a654f0 00007fe39656d0c9 
> 00007fe39656ce6e 00007fe3969a9a55
> (XEN) [2015-04-11 14:03:32.682] Xen call trace:
> (XEN) [2015-04-11 14:03:32.695]    [<ffff82d08014c52c>] 
> iommu_do_pci_domctl+0x2dc/0x740
> (XEN) [2015-04-11 14:03:32.718]    [<ffff82d08014900b>] 
> iommu_do_domctl+0x17/0x1a
> (XEN) [2015-04-11 14:03:32.739]    [<ffff82d080161f2d>] 
> arch_do_domctl+0x2469/0x26e1
> (XEN) [2015-04-11 14:03:32.762]    [<ffff82d08010497f>] 
> do_domctl+0x1a1f/0x1d60
> (XEN) [2015-04-11 14:03:32.783]    [<ffff82d080234c6b>] 
> syscall_enter+0xeb/0x145
> (XEN) [2015-04-11 14:03:32.804] 
> (XEN) [2015-04-11 14:03:32.813] Pagetable walk from 0000000000000000:
> (XEN) [2015-04-11 14:03:32.831]  L4[0x000] = 0000000234075067 000000000001f2a8
> (XEN) [2015-04-11 14:03:32.852]  L3[0x000] = 0000000229ad4067 0000000000014c49
> (XEN) [2015-04-11 14:03:32.873]  L2[0x000] = 0000000000000000 
> ffffffffffffffff 
> (XEN) [2015-04-11 14:03:32.894] 
> (XEN) [2015-04-11 14:03:32.903] ****************************************
> (XEN) [2015-04-11 14:03:32.922] Panic on CPU 5:
> (XEN) [2015-04-11 14:03:32.935] FATAL PAGE FAULT
> (XEN) [2015-04-11 14:03:32.948] [error_code=0000]
> (XEN) [2015-04-11 14:03:32.961] Faulting linear address: 0000000000000000
> (XEN) [2015-04-11 14:03:32.981] ****************************************
> (XEN) [2015-04-11 14:03:33.000] 
> (XEN) [2015-04-11 14:03:33.009] Reboot in five seconds...
>
> The RIP resolves to the prink added by your patch in:
>
>     case XEN_DOMCTL_test_assign_device:
>         ret = xsm_test_assign_device(XSM_HOOK, 
> domctl->u.assign_device.machine_sbdf);
>         if ( ret )
>             break;
>
>         seg = domctl->u.assign_device.machine_sbdf >> 16;
>         bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
>         devfn = domctl->u.assign_device.machine_sbdf & 0xff;
>
>         printk("*** %pv->d%d: test_assign_device({%04x:%02x:%02x.%u})\n",
>                current, d->domain_id,
>                seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>
>         if ( device_assigned(seg, bus, devfn) )
>         {
>             printk(XENLOG_G_INFO
>                    "%04x:%02x:%02x.%u already assigned, or non-existent\n",
>                    seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>             ret = -EINVAL;
>         }
>         break;

hmm - 'd' is NULL.  This ought to work better.

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 9f3413c..85ff1fc 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1532,6 +1532,11 @@ int iommu_do_pci_domctl(
         max_sdevs = domctl->u.get_device_group.max_sdevs;
         sdevs = domctl->u.get_device_group.sdev_array;
 
+        printk("*** %pv->d%d: get_device_group({%04x:%02x:%02x.%u, %u})\n",
+               current, d->domain_id,
+               seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
+               max_sdevs);
+
         ret = iommu_get_device_group(d, seg, bus, devfn, sdevs, max_sdevs);
         if ( ret < 0 )
         {
@@ -1558,6 +1563,9 @@ int iommu_do_pci_domctl(
         bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
         devfn = domctl->u.assign_device.machine_sbdf & 0xff;
 
+        printk("*** %pv: test_assign_device({%04x:%02x:%02x.%u})\n",
+               current, seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
+
         if ( device_assigned(seg, bus, devfn) )
         {
             printk(XENLOG_G_INFO
@@ -1582,6 +1590,10 @@ int iommu_do_pci_domctl(
         bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
         devfn = domctl->u.assign_device.machine_sbdf & 0xff;
 
+        printk("*** %pv->d%d: assign_device({%04x:%02x:%02x.%u})\n",
+               current, d->domain_id,
+               seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
+
         ret = device_assigned(seg, bus, devfn) ?:
               assign_device(d, seg, bus, devfn);
         if ( ret == -ERESTART )
@@ -1604,6 +1616,10 @@ int iommu_do_pci_domctl(
         bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
         devfn = domctl->u.assign_device.machine_sbdf & 0xff;
 
+        printk("*** %pv->d%d: deassign_device({%04x:%02x:%02x.%u})\n",
+               current, d->domain_id,
+               seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
+
         spin_lock(&pcidevs_lock);
         ret = deassign_device(d, seg, bus, devfn);
         spin_unlock(&pcidevs_lock);


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