1. 22 Feb, 2018 1 commit
    • Joao Martins's avatar
      xenbus: track caller request id · 0f0fd007
      Joao Martins authored
      commit 29fee6ee upstream.
      Commit fd8aa909 ("xen: optimize xenbus driver for multiple concurrent
      xenstore accesses") optimized xenbus concurrent accesses but in doing so
      broke UABI of /dev/xen/xenbus. Through /dev/xen/xenbus applications are in
      charge of xenbus message exchange with the correct header and body. Now,
      after the mentioned commit the replies received by application will no
      longer have the header req_id echoed back as it was on request (see
      specification below for reference), because that particular field is being
      overwritten by kernel.
      struct xsd_sockmsg
        uint32_t type;  /* XS_??? */
        uint32_t req_id;/* Request identifier, echoed in daemon's response.  */
        uint32_t tx_id; /* Transaction id (0 if not related to a transaction). */
        uint32_t len;   /* Length of data following this. */
        /* Generally followed by nul-terminated string(s). */
      Before there was only one request at a time so req_id could simply be
      forwarded back and forth. To allow simultaneous requests we need a
      different req_id for each message thus kernel keeps a monotonic increasing
      counter for this field and is written on every request irrespective of
      userspace value.
      Forwarding again the req_id on userspace requests is not a solution because
      we would open the possibility of userspace-generated req_id colliding with
      kernel ones. So this patch instead takes another route which is to
      artificially keep user req_id while keeping the xenbus logic as is. We do
      that by saving the original req_id before xs_send(), use the private kernel
      counter as req_id and then once reply comes and was validated, we restore
      back the original req_id.
      Cc: <stable@vger.kernel.org> # 4.11
      Fixes: fd8aa909 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
      Reported-by: default avatarBhavesh Davda <bhavesh.davda@oracle.com>
      Signed-off-by: default avatarJoao Martins <joao.m.martins@oracle.com>
      Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
      Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
  2. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      Many source files in the tree are missing licensing information, which
      makes it harder for compliance tools to determine the correct license.
      By default all files without license information are under the default
      license of the kernel, which is GPL version 2.
      Update the files which contain no license information with the 'GPL-2.0'
      SPDX license identifier.  The SPDX identifier is a legally binding
      shorthand, which can be used instead of the full boiler plate text.
      This patch is based on work done by Thomas Gleixner and Kate Stewart and
      Philippe Ombredanne.
      How this work was done:
      Patches were generated and checked against linux-4.14-rc6 for a subset of
      the use cases:
       - file had no licensing information it it.
       - file was a */uapi/* one with no licensing information in it,
       - file was a */uapi/* one with existing licensing information,
      Further patches will be generated in subsequent months to fix up cases
      where non-standard license headers were used, and references to license
      had to be inferred by heuristics based on keywords.
      The analysis to determine which SPDX License Identifier to be applied to
      a file was done in a spreadsheet of side by side results from of the
      output of two independent scanners (ScanCode & Windriver) producing SPDX
      tag:value files created by Philippe Ombredanne.  Philippe prepared the
      base worksheet, and did an initial spot review of a few 1000 files.
      The 4.13 kernel was the starting point of the analysis with 60,537 files
      assessed.  Kate Stewart did a file by file comparison of the scanner
      results in the spreadsheet to determine which SPDX license identifier(s)
      to be applied to the file. She confirmed any determination that was not
      immediately clear with lawyers working with the Linux Foundation.
      Criteria used to select files for SPDX license identifier tagging was:
       - Files considered eligible had to be source code files.
       - Make and config files were included as candidates if they contained >5
         lines of source
       - File already had some variant of a license header in it (even if <5
      All documentation files were explicitly excluded.
      The following heuristics were used to determine which SPDX license
      identifiers to apply.
       - when both scanners couldn't find any license traces, file was
         considered to have no license information in it, and the top level
         COPYING file license applied.
         For non */uapi/* files that summary was:
         SPDX license identifier                            # files
         GPL-2.0                                              11139
         and resulted in the first patch in this series.
         If that file was a */uapi/* path one, it was "GPL-2.0 WITH
         Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
         SPDX license identifier                            # files
         GPL-2.0 WITH Linux-syscall-note                        930
         and resulted in the second patch in this series.
       - if a file had some form of licensing information in it, and was one
         of the */uapi/* ones, it was denoted with the Linux-syscall-note if
         any GPL family license was found in the file or had no licensing in
         it (per prior point).  Results summary:
         SPDX license identifier                            # files
         GPL-2.0 WITH Linux-syscall-note                       270
         GPL-2.0+ WITH Linux-syscall-note                      169
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
         LGPL-2.1+ WITH Linux-syscall-note                      15
         GPL-1.0+ WITH Linux-syscall-note                       14
         ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
         LGPL-2.0+ WITH Linux-syscall-note                       4
         LGPL-2.1 WITH Linux-syscall-note                        3
         ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
         ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
         and that resulted in the third patch in this series.
       - when the two scanners agreed on the detected license(s), that became
         the concluded license(s).
       - when there was disagreement between the two scanners (one detected a
         license but the other didn't, or they both detected different
         licenses) a manual inspection of the file occurred.
       - In most cases a manual inspection of the information in the file
         resulted in a clear resolution of the license that should apply (and
         which scanner probably needed to revisit its heuristics).
       - When it was not immediately clear, the license identifier was
         confirmed with lawyers working with the Linux Foundation.
       - If there was any question as to the appropriate license identifier,
         the file was flagged for further research and to be revisited later
         in time.
      In total, over 70 hours of logged manual review was done on the
      spreadsheet to determine the SPDX license identifiers to apply to the
      source files by Kate, Philippe, Thomas and, in some cases, confirmation
      by lawyers working with the Linux Foundation.
      Kate also obtained a third independent scan of the 4.13 code base from
      FOSSology, and compared selected files where the other two scanners
      disagreed against that SPDX file, to see if there was new insights.  The
      Windriver scanner is based on an older version of FOSSology in part, so
      they are related.
      Thomas did random spot checks in about 500 files from the spreadsheets
      for the uapi headers and agreed with SPDX license identifier in the
      files he inspected. For the non-uapi files Thomas did random spot checks
      in about 15000 files.
      In initial set of patches against 4.14-rc6, 3 files were found to have
      copy/paste license identifier errors, and have been fixed to reflect the
      correct identifier.
      Additionally Philippe spent 10 hours this week doing a detailed manual
      inspection and review of the 12,461 patched files from the initial patch
      version early this week with:
       - a full scancode scan run, collecting the matched texts, detected
         license ids and scores
       - reviewing anything where there was a license detected (about 500+
         files) to ensure that the applied SPDX license was correct
       - reviewing anything where there was no detection but the patch license
         was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
         SPDX license was correct
      This produced a worksheet with 20 files needing minor correction.  This
      worksheet was then exported into 3 different .csv files for the
      different types of files to be modified.
      These .csv files were then reviewed by Greg.  Thomas wrote a script to
      parse the csv files and add the proper SPDX tag to the file, in the
      format that the file expected.  This script was further refined by Greg
      based on the output to detect more types of files automatically and to
      distinguish between header and source .c files (which need different
      comment types.)  Finally Greg ran the script using the .csv files to
      generate the patches.
      Reviewed-by: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
  3. 26 Oct, 2017 1 commit
  4. 25 Oct, 2017 1 commit
  5. 28 Sep, 2017 1 commit
  6. 18 Sep, 2017 1 commit
  7. 14 Sep, 2017 1 commit
    • Michal Hocko's avatar
      mm: treewide: remove GFP_TEMPORARY allocation flag · 0ee931c4
      Michal Hocko authored
      GFP_TEMPORARY was introduced by commit e12ba74d ("Group short-lived
      and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
      primary motivation was to allow users to tell that an allocation is
      short lived and so the allocator can try to place such allocations close
      together and prevent long term fragmentation.  As much as this sounds
      like a reasonable semantic it becomes much less clear when to use the
      highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
      context holding that memory sleep? Can it take locks? It seems there is
      no good answer for those questions.
      The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
      __GFP_RECLAIMABLE which in itself is tricky because basically none of
      the existing caller provide a way to reclaim the allocated memory.  So
      this is rather misleading and hard to evaluate for any benefits.
      I have checked some random users and none of them has added the flag
      with a specific justification.  I suspect most of them just copied from
      other existing users and others just thought it might be a good idea to
      use without any measuring.  This suggests that GFP_TEMPORARY just
      motivates for cargo cult usage without any reasoning.
      I believe that our gfp flags are quite complex already and especially
      those with highlevel semantic should be clearly defined to prevent from
      confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
      replace all existing users to simply use GFP_KERNEL.  Please note that
      SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
      so they will be placed properly for memory fragmentation prevention.
      I can see reasons we might want some gfp flag to reflect shorterm
      allocations but I propose starting from a clear semantic definition and
      only then add users with proper justification.
      This was been brought up before LSF this year by Matthew [1] and it
      turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
      seems to be a heuristic without any measured advantage for most (if not
      all) its current users.  The follow up discussion has revealed that
      opinions on what might be temporary allocation differ a lot between
      developers.  So rather than trying to tweak existing users into a
      semantic which they haven't expected I propose to simply remove the flag
      and start from scratch if we really need a semantic for short term
      [1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org
      [akpm@linux-foundation.org: fix typo]
      [akpm@linux-foundation.org: coding-style fixes]
      [sfr@canb.auug.org.au: drm/i915: fix up]
        Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
      Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Acked-by: default avatarMel Gorman <mgorman@suse.de>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Neil Brown <neilb@suse.de>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 31 Aug, 2017 22 commits
  9. 29 Aug, 2017 1 commit
  10. 28 Aug, 2017 1 commit
  11. 21 Aug, 2017 1 commit
    • Arnd Bergmann's avatar
      Kbuild: use -fshort-wchar globally · 8c97023c
      Arnd Bergmann authored
      Commit 971a69db ("Xen: don't warn about 2-byte wchar_t in efi")
      added the --no-wchar-size-warning to the Makefile to avoid this
      harmless warning:
      arm-linux-gnueabi-ld: warning: drivers/xen/efi.o uses 2-byte wchar_t yet the output is to use 4-byte wchar_t; use of wchar_t values across objects may fail
      Changing kbuild to use thin archives instead of recursive linking
      unfortunately brings the same warning back during the final link.
      The kernel does not use wchar_t string literals at this point, and
      xen does not use wchar_t at all (only efi_char16_t), so the flag
      has no effect, but as pointed out by Jan Beulich, adding a wchar_t
      string literal would be bad here.
      Since wchar_t is always defined as u16, independent of the toolchain
      default, always passing -fshort-wchar is correct and lets us
      remove the Xen specific hack along with fixing the warning.
      Link: https://patchwork.kernel.org/patch/9275217/
      Fixes: 971a69db ("Xen: don't warn about 2-byte wchar_t in efi")
      Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
      Acked-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
      Signed-off-by: Masahiro Yamada's avatarMasahiro Yamada <yamada.masahiro@socionext.com>
  12. 15 Aug, 2017 1 commit
    • Roger Pau Monne's avatar
      xen: fix bio vec merging · 462cdace
      Roger Pau Monne authored
      The current test for bio vec merging is not fully accurate and can be
      tricked into merging bios when certain grant combinations are used.
      The result of these malicious bio merges is a bio that extends past
      the memory page used by any of the originating bios.
      Take into account the following scenario, where a guest creates two
      grant references that point to the same mfn, ie: grant 1 -> mfn A,
      grant 2 -> mfn A.
      These references are then used in a PV block request, and mapped by
      the backend domain, thus obtaining two different pfns that point to
      the same mfn, pfn B -> mfn A, pfn C -> mfn A.
      If those grants happen to be used in two consecutive sectors of a disk
      IO operation becoming two different bios in the backend domain, the
      checks in xen_biovec_phys_mergeable will succeed, because bfn1 == bfn2
      (they both point to the same mfn). However due to the bio merging,
      the backend domain will end up with a bio that expands past mfn A into
      mfn A + 1.
      Fix this by making sure the check in xen_biovec_phys_mergeable takes
      into account the offset and the length of the bio, this basically
      replicates whats done in __BIOVEC_PHYS_MERGEABLE using mfns (bus
      addresses). While there also remove the usage of
      __BIOVEC_PHYS_MERGEABLE, since that's already checked by the callers
      of xen_biovec_phys_mergeable.
      CC: stable@vger.kernel.org
      Reported-by: default avatar"Jan H. Schönherr" <jschoenh@amazon.de>
      Signed-off-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
      Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
      Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  13. 11 Aug, 2017 2 commits
    • Liu Shuo's avatar
      xen/events: Fix interrupt lost during irq_disable and irq_enable · 020db9d3
      Liu Shuo authored
      Here is a device has xen-pirq-MSI interrupt. Dom0 might lost interrupt
      during driver irq_disable/irq_enable. Here is the scenario,
       1. irq_disable -> disable_dynirq -> mask_evtchn(irq channel)
       2. dev interrupt raised by HW and Xen mark its evtchn as pending
       3. irq_enable -> startup_pirq -> eoi_pirq ->
          clear_evtchn(channel of irq) -> clear pending status
       4. consume_one_event process the irq event without pending bit assert
          which result in interrupt lost once
       5. No HW interrupt raising anymore.
      Now use enable_dynirq for enable_pirq of xen_pirq_chip to remove
      eoi_pirq when irq_enable.
      Signed-off-by: default avatarLiu Shuo <shuo.a.liu@intel.com>
      Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
      Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
    • Juergen Gross's avatar
      xen: avoid deadlock in xenbus · 529871bb
      Juergen Gross authored
      When starting the xenwatch thread a theoretical deadlock situation is
      xs_init() contains:
          task = kthread_run(xenwatch_thread, NULL, "xenwatch");
          if (IS_ERR(task))
              return PTR_ERR(task);
          xenwatch_pid = task->pid;
      And xenwatch_thread() does:
      The callback could call unregister_xenbus_watch() which does:
          if (current->pid != xenwatch_pid)
      In case a watch is firing before xenwatch_pid could be set and the
      callback of that watch unregisters a watch, then a self-deadlock would
      Avoid this by setting xenwatch_pid in xenwatch_thread().
      Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
      Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
      Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
  14. 27 Jul, 2017 3 commits
  15. 23 Jul, 2017 2 commits