flight 144728 xen-4.10-testing real [real]
http://logs.test-lab.xenproject.org/osstest/logs/144728/

Regressions :-(

Tests which did not succeed and are blocking,
including tests which could not be run:
 test-amd64-i386-xl-qemut-debianhvm-i386-xsm 13 guest-saverestore fail REGR. 
vs. 144324
 test-armhf-armhf-xl-vhd      10 debian-di-install        fail REGR. vs. 144324

Tests which did not succeed, but are not blocking:
 test-amd64-i386-xl-qemut-ws16-amd64 17 guest-stop             fail like 144324
 test-amd64-amd64-xl-qemuu-dmrestrict-amd64-dmrestrict 10 debian-hvm-install 
fail never pass
 test-amd64-i386-xl-qemuu-dmrestrict-amd64-dmrestrict 10 debian-hvm-install 
fail never pass
 test-amd64-i386-libvirt-xsm  13 migrate-support-check        fail   never pass
 test-amd64-amd64-libvirt     13 migrate-support-check        fail   never pass
 test-amd64-amd64-libvirt-xsm 13 migrate-support-check        fail   never pass
 test-amd64-i386-libvirt      13 migrate-support-check        fail   never pass
 test-amd64-i386-libvirt-qemuu-debianhvm-amd64-xsm 11 migrate-support-check 
fail never pass
 test-amd64-amd64-libvirt-qemuu-debianhvm-amd64-xsm 11 migrate-support-check 
fail never pass
 test-arm64-arm64-xl-credit2  13 migrate-support-check        fail   never pass
 test-arm64-arm64-xl-credit2  14 saverestore-support-check    fail   never pass
 test-arm64-arm64-xl-xsm      13 migrate-support-check        fail   never pass
 test-arm64-arm64-xl-xsm      14 saverestore-support-check    fail   never pass
 test-arm64-arm64-libvirt-xsm 13 migrate-support-check        fail   never pass
 test-arm64-arm64-xl          13 migrate-support-check        fail   never pass
 test-arm64-arm64-libvirt-xsm 14 saverestore-support-check    fail   never pass
 test-arm64-arm64-xl          14 saverestore-support-check    fail   never pass
 test-arm64-arm64-xl-credit1  13 migrate-support-check        fail   never pass
 test-arm64-arm64-xl-credit1  14 saverestore-support-check    fail   never pass
 test-arm64-arm64-xl-seattle  13 migrate-support-check        fail   never pass
 test-arm64-arm64-xl-seattle  14 saverestore-support-check    fail   never pass
 test-amd64-amd64-libvirt-vhd 12 migrate-support-check        fail   never pass
 test-armhf-armhf-xl-arndale  13 migrate-support-check        fail   never pass
 test-armhf-armhf-xl-arndale  14 saverestore-support-check    fail   never pass
 test-armhf-armhf-xl-credit2  13 migrate-support-check        fail   never pass
 test-armhf-armhf-xl-multivcpu 13 migrate-support-check        fail  never pass
 test-armhf-armhf-xl-credit2  14 saverestore-support-check    fail   never pass
 test-armhf-armhf-xl-multivcpu 14 saverestore-support-check    fail  never pass
 test-armhf-armhf-libvirt     13 migrate-support-check        fail   never pass
 test-armhf-armhf-libvirt     14 saverestore-support-check    fail   never pass
 test-armhf-armhf-libvirt-raw 12 migrate-support-check        fail   never pass
 test-armhf-armhf-libvirt-raw 13 saverestore-support-check    fail   never pass
 test-amd64-amd64-xl-qemut-win7-amd64 17 guest-stop             fail never pass
 test-amd64-amd64-qemuu-nested-amd 22 leak-check/check          fail never pass
 test-armhf-armhf-xl-credit1  13 migrate-support-check        fail   never pass
 test-armhf-armhf-xl-credit1  14 saverestore-support-check    fail   never pass
 test-armhf-armhf-xl-cubietruck 13 migrate-support-check        fail never pass
 test-armhf-armhf-xl-cubietruck 14 saverestore-support-check    fail never pass
 test-armhf-armhf-xl          13 migrate-support-check        fail   never pass
 test-armhf-armhf-xl          14 saverestore-support-check    fail   never pass
 test-amd64-amd64-xl-qemut-ws16-amd64 17 guest-stop             fail never pass
 test-amd64-i386-xl-qemut-win7-amd64 17 guest-stop              fail never pass
 test-amd64-i386-xl-qemuu-win7-amd64 17 guest-stop              fail never pass
 test-armhf-armhf-xl-rtds     13 migrate-support-check        fail   never pass
 test-armhf-armhf-xl-rtds     14 saverestore-support-check    fail   never pass
 test-amd64-amd64-xl-qemuu-win7-amd64 17 guest-stop             fail never pass
 test-amd64-i386-xl-qemuu-ws16-amd64 17 guest-stop              fail never pass
 test-amd64-amd64-xl-qemuu-ws16-amd64 17 guest-stop             fail never pass
 test-arm64-arm64-xl-thunderx  2 hosts-allocate               starved  n/a

version targeted for testing:
 xen                  6cb1cb9c63e91b71ce639e7b7cf08ca85d44266f
baseline version:
 xen                  e4899550ff7834e1ea5dfbbfb1c618f64e247761

Last test of basis   144324  2019-11-27 12:48:37 Z   15 days
Testing same since   144728  2019-12-11 15:10:47 Z    1 days    1 attempts

------------------------------------------------------------
People who touched revisions under test:
  Andrew Cooper <andrew.coop...@citrix.com>
  George Dunlap <george.dun...@citrix.com>
  Jan Beulich <jbeul...@suse.com>
  Julien Grall <jul...@xen.org>
  Kevin Tian <kevin.t...@intel.com>

jobs:
 build-amd64-xsm                                              pass    
 build-arm64-xsm                                              pass    
 build-i386-xsm                                               pass    
 build-amd64-xtf                                              pass    
 build-amd64                                                  pass    
 build-arm64                                                  pass    
 build-armhf                                                  pass    
 build-i386                                                   pass    
 build-amd64-libvirt                                          pass    
 build-arm64-libvirt                                          pass    
 build-armhf-libvirt                                          pass    
 build-i386-libvirt                                           pass    
 build-amd64-prev                                             pass    
 build-i386-prev                                              pass    
 build-amd64-pvops                                            pass    
 build-arm64-pvops                                            pass    
 build-armhf-pvops                                            pass    
 build-i386-pvops                                             pass    
 test-xtf-amd64-amd64-1                                       pass    
 test-xtf-amd64-amd64-2                                       pass    
 test-xtf-amd64-amd64-3                                       pass    
 test-xtf-amd64-amd64-4                                       pass    
 test-xtf-amd64-amd64-5                                       pass    
 test-amd64-amd64-xl                                          pass    
 test-arm64-arm64-xl                                          pass    
 test-armhf-armhf-xl                                          pass    
 test-amd64-i386-xl                                           pass    
 test-amd64-amd64-libvirt-qemuu-debianhvm-amd64-xsm           pass    
 test-amd64-i386-libvirt-qemuu-debianhvm-amd64-xsm            pass    
 test-amd64-amd64-xl-qemut-stubdom-debianhvm-amd64-xsm        pass    
 test-amd64-i386-xl-qemut-stubdom-debianhvm-amd64-xsm         pass    
 test-amd64-amd64-xl-qemut-debianhvm-i386-xsm                 pass    
 test-amd64-i386-xl-qemut-debianhvm-i386-xsm                  fail    
 test-amd64-amd64-xl-qemuu-debianhvm-i386-xsm                 pass    
 test-amd64-i386-xl-qemuu-debianhvm-i386-xsm                  pass    
 test-amd64-amd64-libvirt-xsm                                 pass    
 test-arm64-arm64-libvirt-xsm                                 pass    
 test-amd64-i386-libvirt-xsm                                  pass    
 test-amd64-amd64-xl-xsm                                      pass    
 test-arm64-arm64-xl-xsm                                      pass    
 test-amd64-i386-xl-xsm                                       pass    
 test-amd64-amd64-qemuu-nested-amd                            fail    
 test-amd64-amd64-xl-pvhv2-amd                                pass    
 test-amd64-i386-qemut-rhel6hvm-amd                           pass    
 test-amd64-i386-qemuu-rhel6hvm-amd                           pass    
 test-amd64-amd64-xl-qemut-debianhvm-amd64                    pass    
 test-amd64-i386-xl-qemut-debianhvm-amd64                     pass    
 test-amd64-amd64-xl-qemuu-debianhvm-amd64                    pass    
 test-amd64-i386-xl-qemuu-debianhvm-amd64                     pass    
 test-amd64-i386-freebsd10-amd64                              pass    
 test-amd64-amd64-xl-qemuu-ovmf-amd64                         pass    
 test-amd64-i386-xl-qemuu-ovmf-amd64                          pass    
 test-amd64-amd64-xl-qemut-win7-amd64                         fail    
 test-amd64-i386-xl-qemut-win7-amd64                          fail    
 test-amd64-amd64-xl-qemuu-win7-amd64                         fail    
 test-amd64-i386-xl-qemuu-win7-amd64                          fail    
 test-amd64-amd64-xl-qemut-ws16-amd64                         fail    
 test-amd64-i386-xl-qemut-ws16-amd64                          fail    
 test-amd64-amd64-xl-qemuu-ws16-amd64                         fail    
 test-amd64-i386-xl-qemuu-ws16-amd64                          fail    
 test-armhf-armhf-xl-arndale                                  pass    
 test-amd64-amd64-xl-credit1                                  pass    
 test-arm64-arm64-xl-credit1                                  pass    
 test-armhf-armhf-xl-credit1                                  pass    
 test-amd64-amd64-xl-credit2                                  pass    
 test-arm64-arm64-xl-credit2                                  pass    
 test-armhf-armhf-xl-credit2                                  pass    
 test-armhf-armhf-xl-cubietruck                               pass    
 test-amd64-amd64-xl-qemuu-dmrestrict-amd64-dmrestrict        fail    
 test-amd64-i386-xl-qemuu-dmrestrict-amd64-dmrestrict         fail    
 test-amd64-i386-freebsd10-i386                               pass    
 test-amd64-amd64-qemuu-nested-intel                          pass    
 test-amd64-amd64-xl-pvhv2-intel                              pass    
 test-amd64-i386-qemut-rhel6hvm-intel                         pass    
 test-amd64-i386-qemuu-rhel6hvm-intel                         pass    
 test-amd64-amd64-libvirt                                     pass    
 test-armhf-armhf-libvirt                                     pass    
 test-amd64-i386-libvirt                                      pass    
 test-amd64-amd64-livepatch                                   pass    
 test-amd64-i386-livepatch                                    pass    
 test-amd64-amd64-migrupgrade                                 pass    
 test-amd64-i386-migrupgrade                                  pass    
 test-amd64-amd64-xl-multivcpu                                pass    
 test-armhf-armhf-xl-multivcpu                                pass    
 test-amd64-amd64-pair                                        pass    
 test-amd64-i386-pair                                         pass    
 test-amd64-amd64-libvirt-pair                                pass    
 test-amd64-i386-libvirt-pair                                 pass    
 test-amd64-amd64-amd64-pvgrub                                pass    
 test-amd64-amd64-i386-pvgrub                                 pass    
 test-amd64-amd64-pygrub                                      pass    
 test-amd64-amd64-xl-qcow2                                    pass    
 test-armhf-armhf-libvirt-raw                                 pass    
 test-amd64-i386-xl-raw                                       pass    
 test-amd64-amd64-xl-rtds                                     pass    
 test-armhf-armhf-xl-rtds                                     pass    
 test-arm64-arm64-xl-seattle                                  pass    
 test-amd64-amd64-xl-qemuu-debianhvm-amd64-shadow             pass    
 test-amd64-i386-xl-qemuu-debianhvm-amd64-shadow              pass    
 test-amd64-amd64-xl-shadow                                   pass    
 test-amd64-i386-xl-shadow                                    pass    
 test-arm64-arm64-xl-thunderx                                 starved 
 test-amd64-amd64-libvirt-vhd                                 pass    
 test-armhf-armhf-xl-vhd                                      fail    


------------------------------------------------------------
sg-report-flight on osstest.test-lab.xenproject.org
logs: /home/logs/logs
images: /home/logs/images

Logs, config files, etc. are available at
    http://logs.test-lab.xenproject.org/osstest/logs

Explanation of these reports, and of osstest in general, is at
    http://xenbits.xen.org/gitweb/?p=osstest.git;a=blob;f=README.email;hb=master
    http://xenbits.xen.org/gitweb/?p=osstest.git;a=blob;f=README;hb=master

Test harness code can be found at
    http://xenbits.xen.org/gitweb?p=osstest.git;a=summary


Not pushing.

------------------------------------------------------------
commit 6cb1cb9c63e91b71ce639e7b7cf08ca85d44266f
Author: Andrew Cooper <andrew.coop...@citrix.com>
Date:   Wed Dec 11 15:44:09 2019 +0100

    AMD/IOMMU: Cease using a dynamic height for the IOMMU pagetables
    
    update_paging_mode() has multiple bugs:
    
     1) Booting with iommu=debug will cause it to inform you that that it called
        without the pdev_list lock held.
     2) When growing by more than a single level, it leaks the newly allocated
        table(s) in the case of a further error.
    
    Furthermore, the choice of default level for a domain has issues:
    
     1) All HVM guests grow from 2 to 3 levels during construction because of 
the
        position of the VRAM just below the 4G boundary, so defaulting to 2 is a
        waste of effort.
     2) The limit for PV guests doesn't take memory hotplug into account, and
        isn't dynamic at runtime like HVM guests.  This means that a PV guest 
may
        get RAM which it can't map in the IOMMU.
    
    The dynamic height is a property unique to AMD, and adds a substantial
    quantity of complexity for what is a marginal performance improvement.  
Remove
    the complexity by removing the dynamic height.
    
    PV guests now get 3 or 4 levels based on any hotplug regions in the host.
    This only makes a difference for hardware which previously had all RAM below
    the 512G boundary, and a hotplug region above.
    
    HVM guests now get 4 levels (which will be sufficient until 256TB guests
    become a thing), because we don't currently have the information to know 
when
    3 would be safe to use.
    
    The overhead of this extra level is not expected to be noticeable.  It costs
    one page (4k) per domain, and one extra IO-TLB paging structure cache entry
    which is very hot and less likely to be evicted.
    
    This is XSA-311.
    
    Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
    Acked-by: Jan Beulich <jbeul...@suse.com>
    master commit: b4f042236ae0bb6725b3e8dd40af5a2466a6f971
    master date: 2019-12-11 14:55:32 +0100

commit ba2776a1c19ea3bd17d1b20fac9710a70d478981
Author: George Dunlap <george.dun...@citrix.com>
Date:   Wed Dec 11 15:43:44 2019 +0100

    x86/mm: relinquish_memory: Grab an extra type ref when setting PGT_partial
    
    The PGT_partial bit in page->type_info holds both a type count and a
    general ref count.  During domain tear-down, when free_page_type()
    returns -ERESTART, relinquish_memory() correctly handles the general
    ref count, but fails to grab an extra type count when setting
    PGT_partial.  When this bit is eventually cleared, type_count underflows
    and triggers the following BUG in page_alloc.c:free_domheap_pages():
    
        BUG_ON((pg[i].u.inuse.type_info & PGT_count_mask) != 0);
    
    As far as we can tell, this page underflow cannot be exploited any any
    other way: The page can't be used as a pagetable by the dying domain
    because it's dying; it can't be used as a pagetable by any other
    domain since it belongs to the dying domain; and ownership can't
    transfer to any other domain without hitting the BUG_ON() in
    free_domheap_pages().
    
    (steal_page() won't work on a page in this state, since it requires
    PGC_allocated to be set, and PGC_allocated will already have been
    cleared.)
    
    Fix this by grabbing an extra type ref if setting PGT_partial in
    relinquish_memory.
    
    This is part of XSA-310.
    
    Signed-off-by: George Dunlap <george.dun...@citrix.com>
    Acked-by: Jan Beulich <jbeul...@suse.com>
    master commit: 66bdc16aeed8ddb2ae724adc5ea6bde0dea78c3d
    master date: 2019-12-11 14:55:08 +0100

commit 9d143e84c2a3f1b9bb1783cf64769faab0b11625
Author: George Dunlap <george.dun...@citrix.com>
Date:   Wed Dec 11 15:43:09 2019 +0100

    x86/mm: alloc/free_lN_table: Retain partial_flags on -EINTR
    
    When validating or de-validating pages (in alloc_lN_table and
    free_lN_table respectively), the `partial_flags` local variable is
    used to keep track of whether the "current" PTE started the entire
    operation in a "may be partial" state.
    
    One of the patches in XSA-299 addressed the fact that it is possible
    for a previously-partially-validated entry to subsequently be found to
    have invalid entries (indicated by returning -EINVAL); in which case
    page->partial_flags needs to be set to indicate that the current PTE
    may have the partial bit set (and thus _put_page_type() should be
    called with PTF_partial_set).
    
    Unfortunately, the patches in XSA-299 assumed that once
    put_page_from_lNe() returned -ERESTART on a page, it was not possible
    for it to return -EINTR.  This turns out to be true for
    alloc_lN_table() and free_lN_table, but not for _get_page_type() and
    _put_page_type(): both can return -EINTR when called on pages with
    PGT_partial set.  In these cases, the pages PGT_partial will still be
    set; failing to set partial_flags appropriately may allow an attacker
    to do a privilege escalation similar to those described in XSA-299.
    
    Fix this by always copying the local partial_flags variable into
    page->partial_flags when exiting early.
    
    NB that on the "get" side, no adjustment to nr_validated_entries is
    needed: whether pte[i] is partially validated or entirely
    un-validated, we want nr_validated_entries = i.  On the "put" side,
    however, we need to adjust nr_validated_entries appropriately: if
    pte[i] is entirely validated, we want nr_validated_entries = i + 1; if
    pte[i] is partially validated, we want nr_validated_entries = i.
    
    This is part of XSA-310.
    
    Signed-off-by: George Dunlap <george.dun...@citrix.com>
    Reviewed-by: Jan Beulich <jbeul...@suse.com>
    master commit: 4e70f4476c0c543559f971faecdd5f1300cddb0a
    master date: 2019-12-11 14:54:43 +0100

commit fe8dab3cfc821aed3e94b11363a8304bb620c4ef
Author: George Dunlap <george.dun...@citrix.com>
Date:   Wed Dec 11 15:42:33 2019 +0100

    x86/mm: Set old_guest_table when destroying vcpu pagetables
    
    Changeset 6c4efc1eba ("x86/mm: Don't drop a type ref unless you held a
    ref to begin with"), part of XSA-299, changed the calling discipline
    of put_page_type() such that if put_page_type() returned -ERESTART
    (indicating a partially de-validated page), subsequent calls to
    put_page_type() must be called with PTF_partial_set.  If called on a
    partially de-validated page but without PTF_partial_set, Xen will
    BUG(), because to do otherwise would risk opening up the kind of
    privilege escalation bug described in XSA-299.
    
    One place this was missed was in vcpu_destroy_pagetables().
    put_page_and_type_preemptible() is called, but on -ERESTART, the
    entire operation is simply restarted, causing put_page_type() to be
    called on a partially de-validated page without PTF_partial_set.  The
    result was that if such an operation were interrupted, Xen would hit a
    BUG().
    
    Fix this by having vcpu_destroy_pagetables() consistently pass off
    interrupted de-validations to put_old_page_type():
    - Unconditionally clear references to the page, even if
      put_page_and_type failed
    - Set old_guest_table and old_guest_table_partial appropriately
    
    While here, do some refactoring:
    
     - Move clearing of arch.cr3 to the top of the function
    
     - Now that clearing is unconditional, move the unmap to the same
       conditional as the l4tab mapping.  This also allows us to reduce
       the scope of the l4tab variable.
    
     - Avoid code duplication by looping to drop references on
       guest_table_user
    
    This is part of XSA-310.
    
    Reported-by: Sarah Newman <s...@prgmr.com>
    Signed-off-by: George Dunlap <george.dun...@citrix.com>
    Reviewed-by: Jan Beulich <jbeul...@suse.com>
    master commit: ececa12b2c4c8e4433e4f9be83f5c668ae36fe08
    master date: 2019-12-11 14:54:13 +0100

commit 07e546ef49daedb4fb1bcb28c7443533c0675122
Author: George Dunlap <george.dun...@citrix.com>
Date:   Wed Dec 11 15:41:54 2019 +0100

    x86/mm: Don't reset linear_pt_count on partial validation
    
    "Linear pagetables" is a technique which involves either pointing a
    pagetable at itself, or to another pagetable the same or higher level.
    Xen has limited support for linear pagetables: A page may either point
    to itself, or point to another page of the same level (i.e., L2 to L2,
    L3 to L3, and so on).
    
    XSA-240 introduced an additional restriction that limited the "depth"
    of such chains by allowing pages to either *point to* other pages of
    the same level, or *be pointed to* by other pages of the same level,
    but not both.  To implement this, we keep track of the number of
    outstanding times a page points to or is pointed to another page
    table, to prevent both from happening at the same time.
    
    Unfortunately, the original commit introducing this reset this count
    when resuming validation of a partially-validated pagetable, dropping
    some "linear_pt_entry" counts.
    
    On debug builds on systems where guests used this feature, this might
    lead to crashes that look like this:
    
        Assertion 'oc > 0' failed at mm.c:874
    
    Worse, if an attacker could engineer such a situation to occur, they
    might be able to make loops or other abitrary chains of linear
    pagetables, leading to the denial-of-service situation outlined in
    XSA-240.
    
    This is XSA-309.
    
    Reported-by: Manuel Bouyer <bou...@antioche.eu.org>
    Signed-off-by: George Dunlap <george.dun...@citrix.com>
    Reviewed-by: Jan Beulich <jbeul...@suse.com>
    master commit: 7473efd12fb7a6548f5303f1f4c5cb521543a813
    master date: 2019-12-11 14:10:27 +0100

commit fefa5f92616d8505f6753b5f18fa25aa59c17053
Author: Andrew Cooper <andrew.coop...@citrix.com>
Date:   Wed Dec 11 15:41:22 2019 +0100

    x86/vtx: Work around SingleStep + STI/MovSS VMEntry failures
    
    See patch comment for technical details.
    
    Concerning the timeline, this was first discovered in the aftermath of
    XSA-156 which caused #DB to be intercepted unconditionally, but only in
    its SingleStep + STI form which is restricted to privileged software.
    
    After working with Intel and identifying the problematic vmentry check,
    this workaround was suggested, and the patch was posted in an RFC
    series.  Outstanding work for that series (not breaking Introspection)
    is still pending, and this fix from it (which wouldn't have been good
    enough in its original form) wasn't committed.
    
    A vmentry failure was reported to xen-devel, and debugging identified
    this bug in its SingleStep + MovSS form by way of INT1, which does not
    involve the use of any privileged instructions, and proving this to be a
    security issue.
    
    This is XSA-308
    
    Reported-by: HÃ¥kon Alstadheim <ha...@alstadheim.priv.no>
    Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
    Reviewed-by: Jan Beulich <jbeul...@suse.com>
    Acked-by: Kevin Tian <kevin.t...@intel.com>
    master commit: 1d3eb8259804e5bec991a3462d69ba6bd80bb40e
    master date: 2019-12-11 14:09:30 +0100

commit c9f9ff77a6acd3306f72872ddad32b4bd413ed81
Author: Jan Beulich <jbeul...@suse.com>
Date:   Wed Dec 11 15:40:39 2019 +0100

    x86+Arm32: make find_next_{,zero_}bit() have well defined behavior
    
    These functions getting used with the 2nd and 3rd arguments being equal
    wasn't well defined: Arm64 reliably returns the value of the 2nd
    argument in this case, while on x86 for bitmaps up to 64 bits wide the
    return value was undefined (due to the undefined behavior of a shift of
    a value by the number of bits it's wide) when the incoming value was 64.
    On Arm32 an actual out of bounds access would happen when the
    size/offset value is a multiple of 32; if this access doesn't fault, the
    return value would have been sufficiently correct afaict.
    
    Make the functions consistently tolerate the last two arguments being
    equal (and in fact the 3rd argument being greater or equal to the 2nd),
    in favor of finding and fixing all the use sites that violate the
    original more strict assumption.
    
    This is XSA-307.
    
    Signed-off-by: Jan Beulich <jbeul...@suse.com>
    Acked-by: Julien Grall <jul...@xen.org>
    master commit: 7442006b9f0940fb36f1f8470a416ec836e0d2ce
    master date: 2019-12-11 14:06:18 +0100

commit 406d40d8b4161aecedfb8fd1c3cb74dcdb9419a1
Author: Jan Beulich <jbeul...@suse.com>
Date:   Wed Dec 11 15:39:07 2019 +0100

    AMD/IOMMU: don't needlessly trigger errors/crashes when unmapping a page
    
    Unmapping a page which has never been mapped should be a no-op (note how
    it already is in case there was no root page table allocated). There's
    in particular no need to grow the number of page table levels in use,
    and there's also no need to allocate intermediate page tables except
    when needing to split a large page.
    
    Signed-off-by: Jan Beulich <jbeul...@suse.com>
    Reviewed-by: Paul Durrant <p...@xen.org>
    Acked-by: Andrew Cooper <andrew.coop...@citrix.com>
    master commit: ad591454f069647c36a7daaa9ec23384c0263f0b
    master date: 2019-11-12 11:08:34 +0100
(qemu changes not included)

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