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



Saturday, April 11, 2015, 10:22:16 PM, you wrote:

> On 11/04/2015 20:33, Sander Eikelenboom wrote:
>> Saturday, April 11, 2015, 8:25:52 PM, you wrote:
>>
>>> On 11/04/15 18:42, Sander Eikelenboom wrote:
>>>> Saturday, April 11, 2015, 7:35:57 PM, you wrote:
>>>>
>>>>> On 11/04/15 18:25, Sander Eikelenboom wrote:
>>>>>> Saturday, April 11, 2015, 6:38:17 PM, you wrote:
>>>>>>
>>>>>>> On 11/04/15 17:32, Andrew Cooper wrote:
>>>>>>>> On 11/04/15 17:21, Sander Eikelenboom wrote:
>>>>>>>>> Saturday, April 11, 2015, 4:21:56 PM, you wrote:
>>>>>>>>>
>>>>>>>>>> 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);
>>>>>>>>> Hi Andrew,
>>>>>>>>>
>>>>>>>>> Attached are the serial logs good (with revert) and bad (without):
>>>>>>>>>
>>>>>>>>> Some things that seems strange to me:
>>>>>>>>> - The numerous calls to get the device 08:00.0 assigned ... for 
>>>>>>>>> 0a:00.0 there 
>>>>>>>>>   was only one call to both test assign and assign.
>>>>>>>>> - However these numerous calls are there in both the good and the bad 
>>>>>>>>> case,
>>>>>>>>>   so perhaps it's strange and wrong .. but not the cause ..
>>>>>>>>> - I had a hunch it could be due to the 08:00.0 using MSI-X, but when 
>>>>>>>>> only 
>>>>>>>>>   passing through 0a:00.0, i get the same numerous calls but now for 
>>>>>>>>> the 
>>>>>>>>>   0a:00.0 which uses IntX, so I think that is more related to being 
>>>>>>>>> the *first*
>>>>>>>>>   device to be passed through to a guest.
>>>>>>>> I have also observed this behaviour, but not had time to investigate. 
>>>>>>>> It doesn't appear problematic in the longrun but it probably a 
>>>>>>>> toolstack
>>>>>>>> issue which wants fixing (if only in the name of efficiency).
>>>>>>> And just after I sent this email, I have realised why.
>>>>>>> The first assign device will have to build IO pagetables, which is a
>>>>>>> long operation and subject to hypercall continuations.  The second
>>>>>>> device will reused the same pagetables, so is quick to complete.
>>>>>> So .. is the ioreq patch from Paul involved in providing something used 
>>>>>> in building 
>>>>>> the pagetables .. and could it have say some off by one resulting in the 
>>>>>> 0xffffffffffff .. which could lead to the pagetable building going 
>>>>>> beserk, 
>>>>>> requiring a paging_mode far greater than normally would be required .. 
>>>>>> which 
>>>>>> get's set .. since that isn't checked properly .. leading to things 
>>>>>> breaking 
>>>>>> a bit further when it does get checked ? 
>>>>> A -1 is slipping in somewhere and ending up in the gfn field.
>>>>> The result is that update_paging_mode() attempts to construct
>>>>> iopagetables to cover a 76bit address space, which is how level ends up
>>>>> at 8.  (Note that a level of 7 is reserved, and a level of anything
>>>>> greater than 4 is implausible on your system.)
>>>>> I think the crash is collateral damage following on from
>>>>> update_paging_mode() not properly sanitising its input, but that there
>>>>> is still some other issue causing -1 to be passed in the first place.
>>>>> I am still trying to locate where a -1 might plausibly be coming from.
>>>> I have just added some extra debug code to store the values from the start 
>>>> of update_paging_mode() .. so i can print them at the end if the 
>>>> paging_mode 
>>>> gets out of band and do a dump_stack() as well. Hopefully is will confirm 
>>>> this.
>>> Right - arch_iommu_populate_page_table() is falling over a page
>>> allocated to the domain which doesn't have a valid gfn.
>>> The ioreq server allocates itself some guest pages and then shoots them
>>> out as part of setting the server up.  (This is a kudge to work around
>>> the fact that Xen doesn't have an interface for device models etc to
>>> allocate memory on behalf of the domain which will strictly never find
>>> its way into the guest physmap.)
>>> Can you try this patch and see whether some of the numbers printed out
>>> start matching up?
>>> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
>>> index bfde380..d1adfa7 100644
>>> --- a/xen/arch/x86/hvm/hvm.c
>>> +++ b/xen/arch/x86/hvm/hvm.c
>>> @@ -534,6 +534,10 @@ static int hvm_map_ioreq_page(
>>>  static void hvm_remove_ioreq_gmfn(
>>>      struct domain *d, struct hvm_ioreq_page *iorp)
>>>  {
>>> +    printk("*** %s() d%d, page %p, mfn %lx, gfn %lx, va %p\n",
>>> +           __func__, d->domain_id,
>> +           iorp->>page, page_to_mfn(iorp->page), iorp->gmfn, iorp->va);
>>> +
>>>      guest_physmap_remove_page(d, iorp->gmfn,
>>>                                page_to_mfn(iorp->page), 0);
>>>      clear_page(iorp->va);
>>> diff --git a/xen/drivers/passthrough/x86/iommu.c
>>> b/xen/drivers/passthrough/x86/iommu.c
>>> index 9eb8d33..048a1a9 100644
>>> --- a/xen/drivers/passthrough/x86/iommu.c
>>> +++ b/xen/drivers/passthrough/x86/iommu.c
>>> @@ -59,7 +59,16 @@ int arch_iommu_populate_page_table(struct domain *d)
>>>          if ( has_hvm_container_domain(d) ||
>>>              (page->u.inuse.type_info & PGT_type_mask) ==
>>> PGT_writable_page )
>>>          {
>>> -            BUG_ON(SHARED_M2P(mfn_to_gmfn(d, page_to_mfn(page))));
>>> +            unsigned long mfn = page_to_mfn(page);
>>> +            unsigned long gfn = mfn_to_gmfn(d, mfn);
>>> +
>>> +            BUG_ON(SHARED_M2P(gfn));
>>> +
>>> +            if ( gfn == INVALID_MFN )
>>> +            {
>>> +                printk("*** %s() d%d, page %p, mfn %lx, gfn %lx - about
>>> to break\n",
>>> +                       __func__, d->domain_id, page, mfn, gfn);
>>> +            }
>>>              rc = hd->platform_ops->map_page(
>>>                  d, mfn_to_gmfn(d, page_to_mfn(page)), page_to_mfn(page),
>>>                  IOMMUF_readable|IOMMUF_writable);
>>
>> Ok .. so here we go:
>>
>> (XEN) [2015-04-11 19:24:59.418] *** hvm_remove_ioreq_gmfn() d1, page 
>> ffff82e0049f7700, mfn 24fbb8, gfn feff0, va ffff82c00082b000
>> (XEN) [2015-04-11 19:24:59.452] *** hvm_remove_ioreq_gmfn() d1, page 
>> ffff82e0049f76e0, mfn 24fbb7, gfn feff1, va ffff82c00082d000
>> (XEN) [2015-04-11 19:25:00.158] *** d0v5: test_assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:02.221] io.c:429: d1: bind: m_gsi=47 g_gsi=36 
>> dev=00.00.5 intx=0
>> (XEN) [2015-04-11 19:25:02.248] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:02.268] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:02.290] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:02.310] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:02.333] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:02.353] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:02.375] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:02.395] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> <BIG SNIP>
>> (XEN) [2015-04-11 19:25:45.444] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:45.464] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:45.486] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:45.506] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:45.529] *** d0v1->d1: assign_device({0000:0a:00.0})
>> (XEN) [2015-04-11 19:25:45.549] ?!?!? d1: pci_dev:0000:0a:00.0 
>> hd->arch.paging_mode:2
>> (XEN) [2015-04-11 19:25:45.571] *** arch_iommu_populate_page_table() d1, 
>> page ffff82e0049f7700, mfn 24fbb8, gfn ffffffffffffffff - about to break
>> (XEN) [2015-04-11 19:25:45.610] AMD-Vi: ?!?!? amd_iommu_map_page level 
>> before:3 gfn:0xffffffffffffffff mfn:0x24fbb8 flags:3
>> (XEN) [2015-04-11 19:25:45.642] AMD-Vi: ?!?!? update_paging_mode level 
>> before:3 gfn:0xffffffffffffffff 
>> (XEN) [2015-04-11 19:25:45.669] AMD-Vi: ?!?!? update_paging_mode end: 
>> paging_mode:6 offset:31 root: old_root_mfn:0x11d55b new_root_mfn:0x11d55a 
>> gfn:0xffffffffffffffff req_id:0 PTE_PER_TABLE_SIZE:512 
>> (XEN) [2015-04-11 19:25:45.722] AMD-Vi: ?!?!? update_paging_mode end: values 
>> at start: paging_mode:3 offset:-1 gfn:0xffffffffffffffff 
>> (XEN) [2015-04-11 19:25:45.757] AMD-Vi: ?!?!? amd_iommu_map_page level after 
>> update paging mode:6 gfn:0xffffffffffffffff mfn:0x24fbb8 flags:3
>> (XEN) [2015-04-11 19:25:45.794] AMD-Vi: ?!?!? amd_iommu_map_page level end:6 
>>  gfn:0xffffffffffffffff mfn:0x24fbb8 flags:3
>> (XEN) [2015-04-11 19:25:45.826] *** arch_iommu_populate_page_table() d1, 
>> page ffff82e0049f76e0, mfn 24fbb7, gfn ffffffffffffffff - about to break
>> (XEN) [2015-04-11 19:25:45.864] AMD-Vi: ?!?!? amd_iommu_map_page level 
>> before:6 gfn:0xffffffffffffffff mfn:0x24fbb7 flags:3
>> (XEN) [2015-04-11 19:25:45.897] AMD-Vi: ?!?!? update_paging_mode level 
>> before:6 gfn:0xffffffffffffffff 
>> (XEN) [2015-04-11 19:25:45.924] AMD-Vi: ?!?!? update_paging_mode end: 
>> paging_mode:8 offset:1 root: old_root_mfn:0x11d554 new_root_mfn:0x11d553 
>> gfn:0xffffffffffffffff req_id:0 PTE_PER_TABLE_SIZE:512 
>> (XEN) [2015-04-11 19:25:45.976] AMD-Vi: ?!?!? update_paging_mode end: values 
>> at start: paging_mode:6 offset:524287 gfn:0xffffffffffffffff 
>> (XEN) [2015-04-11 19:25:46.013] AMD-Vi: ?!?!? amd_iommu_map_page level after 
>> update paging mode:8 gfn:0xffffffffffffffff mfn:0x24fbb7 flags:3
>> (XEN) [2015-04-11 19:25:46.050] AMD-Vi: ?!?!? iommu_pde_from_gfn: domid:1 
>> table:1 level:8 pfn:0xffffffffffffffff
>> (XEN) [2015-04-11 19:25:46.079] Xen BUG at iommu_map.c:459
>> (XEN) [2015-04-11 19:25:46.095] ----[ Xen-4.6-unstable  x86_64  debug=y  
>> Tainted:    C ]----
>> (XEN) [2015-04-11 19:25:46.119] CPU:    2
>> (XEN) [2015-04-11 19:25:46.131] RIP:    e008:[<ffff82d080155d03>] 
>> iommu_pde_from_gfn+0x82/0x47a
>> (XEN) [2015-04-11 19:25:46.156] RFLAGS: 0000000000010202   CONTEXT: 
>> hypervisor
>> (XEN) [2015-04-11 19:25:46.177] rax: 0000000000000000   rbx: 
>> 0000000000000008   rcx: 0000000000000000
>> (XEN) [2015-04-11 19:25:46.203] rdx: ffff830256f20000   rsi: 
>> 000000000000000a   rdi: ffff82d0802986c0
>> (XEN) [2015-04-11 19:25:46.230] rbp: ffff830256f27ad8   rsp: 
>> ffff830256f27a78   r8:  ffff830256f30000
>> (XEN) [2015-04-11 19:25:46.257] r9:  0000000000000002   r10: 
>> 0000000000000032   r11: 0000000000000002
>> (XEN) [2015-04-11 19:25:46.284] r12: ffff82e0023aaa60   r13: 
>> 000000000024fb00   r14: 00000000000000e9
>> (XEN) [2015-04-11 19:25:46.311] r15: 00007d2000000000   cr0: 
>> 0000000080050033   cr4: 00000000000006f0
>> (XEN) [2015-04-11 19:25:46.337] cr3: 000000025f176000   cr2: ffff8000007f6800
>> (XEN) [2015-04-11 19:25:46.358] ds: 0000   es: 0000   fs: 0000   gs: 0000   
>> ss: e010   cs: e008
>> (XEN) [2015-04-11 19:25:46.383] Xen stack trace from rsp=ffff830256f27a78:
>> (XEN) [2015-04-11 19:25:46.403]    ffff83025f7bd000 ffff830256f27b30 
>> ffffffffffffffff ffff830200000030
>> (XEN) [2015-04-11 19:25:46.430]    ffff830256f27ae8 ffff830256f27aa8 
>> 0000000000000000 ffff83025f7bd000
>> (XEN) [2015-04-11 19:25:46.457]    ffff82e0049f76e0 000000000024fbb7 
>> 00000000000000e9 00007d2000000000
>> (XEN) [2015-04-11 19:25:46.484]    ffff830256f27b98 ffff82d0801562a9 
>> 0000000000000206 ffff830256f27b08
>> (XEN) [2015-04-11 19:25:46.511]    000000000024fbb7 0000000000000003 
>> ffff83025f7bd938 ffffffffffffffff
>> (XEN) [2015-04-11 19:25:46.538]    ffff83025f7bd000 ffff83025f7bd000 
>> 000000000024fbb7 0000000000000000
>> (XEN) [2015-04-11 19:25:46.565]    0000000000000000 0000000000000000 
>> 0000000000000000 0000000000000000
>> (XEN) [2015-04-11 19:25:46.592]    0000000000000000 0000000000000000 
>> ffff83025f7bd938 ffff83025f7bd000
>> (XEN) [2015-04-11 19:25:46.619]    ffff82e0049f76e0 000000000024fbb7 
>> 00000000000000e9 00007d2000000000
>> (XEN) [2015-04-11 19:25:46.646]    ffff830256f27bf8 ffff82d08015a7f8 
>> 0000000000000000 ffff83025f7bd020
>> (XEN) [2015-04-11 19:25:46.673]    000000000024fbb7 ffff830256f20000 
>> ffff830256f27bf8 0000000000000000
>> (XEN) [2015-04-11 19:25:46.700]    000000000000000a 00007f017c8d1004 
>> 0000000000000000 ffff83025f7bd000
>> (XEN) [2015-04-11 19:25:46.727]    ffff830256f27c98 ffff82d08014c6e1 
>> ffff830200000002 ffff82d08012c178
>> (XEN) [2015-04-11 19:25:46.754]    0000000000000000 ffff830256f27c28 
>> 0000000000000001 0000000000000000
>> (XEN) [2015-04-11 19:25:46.781]    0000000000000000 0000000000000000 
>> 00007f017c8d1004 0000000000000000
>> (XEN) [2015-04-11 19:25:46.808]    ffff82d080331034 ffff830256f20000 
>> 000000000025f176 00007f017c8d1004
>> (XEN) [2015-04-11 19:25:46.835]    ffff83025f7bd000 00007f017c8d1004 
>> ffff83025f7bd000 0000000000000005
>> (XEN) [2015-04-11 19:25:46.863]    ffff830256f27ca8 ffff82d08014900b 
>> ffff830256f27d98 ffff82d080161f2d
>> (XEN) [2015-04-11 19:25:46.890]    000000000023468c 0000000000000002 
>> 0000000000000005 0000000000000001
>> (XEN) [2015-04-11 19:25:46.917]    ffff82d080331bb8 0000000000000001 
>> ffff830256f27de8 ffff82d080120c10
>> (XEN) [2015-04-11 19:25:46.944] Xen call trace:
>> (XEN) [2015-04-11 19:25:46.956]    [<ffff82d080155d03>] 
>> iommu_pde_from_gfn+0x82/0x47a
>> (XEN) [2015-04-11 19:25:46.979]    [<ffff82d0801562a9>] 
>> amd_iommu_map_page+0x1ae/0x5ec
>> (XEN) [2015-04-11 19:25:47.002]    [<ffff82d08015a7f8>] 
>> arch_iommu_populate_page_table+0x164/0x4c3
>> (XEN) [2015-04-11 19:25:47.028]    [<ffff82d08014c6e1>] 
>> iommu_do_pci_domctl+0x491/0x740
>> (XEN) [2015-04-11 19:25:47.051]    [<ffff82d08014900b>] 
>> iommu_do_domctl+0x17/0x1a
>> (XEN) [2015-04-11 19:25:47.073]    [<ffff82d080161f2d>] 
>> arch_do_domctl+0x2469/0x26e1
>> (XEN) [2015-04-11 19:25:47.095]    [<ffff82d08010497f>] 
>> do_domctl+0x1a1f/0x1d60
>> (XEN) [2015-04-11 19:25:47.116]    [<ffff82d080234c6b>] 
>> syscall_enter+0xeb/0x145
>> (XEN) [2015-04-11 19:25:47.137] 
>> (XEN) [2015-04-11 19:25:47.146] 
>> (XEN) [2015-04-11 19:25:47.155] ****************************************
>> (XEN) [2015-04-11 19:25:47.174] Panic on CPU 2:
>> (XEN) [2015-04-11 19:25:47.187] Xen BUG at iommu_map.c:459
>> (XEN) [2015-04-11 19:25:47.203] ****************************************
>> (XEN) [2015-04-11 19:25:47.222] 
>> (XEN) [2015-04-11 19:25:47.231] Reboot in five seconds...
>>  
>>

> Right - does this fix the issue for you?

Affirmative :)
It survives and the device seems to work properly as well,
will do some more tests tomorrow.

Thanks for tracking it down !

--
Sander 


> diff --git a/xen/drivers/passthrough/x86/iommu.c
> b/xen/drivers/passthrough/x86/iommu.c
> index 9eb8d33..6094ba1 100644
> --- a/xen/drivers/passthrough/x86/iommu.c
> +++ b/xen/drivers/passthrough/x86/iommu.c
> @@ -56,8 +56,9 @@ int arch_iommu_populate_page_table(struct domain *d)

>      while ( !rc && (page = page_list_remove_head(&d->page_list)) )
>      {
> -        if ( has_hvm_container_domain(d) ||
-            (page->>u.inuse.type_info & PGT_type_mask) ==
> PGT_writable_page )
> +        if ( (mfn_to_gmfn(d, page_to_mfn(page)) != INVALID_MFN) &&
> +             (has_hvm_container_domain(d) ||
> +              ((page->u.inuse.type_info & PGT_type_mask) ==
> PGT_writable_page)) )
>          {
>              BUG_ON(SHARED_M2P(mfn_to_gmfn(d, page_to_mfn(page))));
>              rc = hd->platform_ops->map_page(





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