linux.git/include/xen, branch master Linux kernel source tree xen/xenbus: better handle backend crash 2026-03-04T14:31:40+00:00 Juergen Gross jgross@suse.com 2026-02-18T09:52:05+00:00 e2dcf9065536ab4a1b00828ff0d19f7d282dfecc When the backend domain crashes, coordinated device cleanup is not possible (as it involves waiting for the backend state change). In that case, toolstack forcefully removes frontend xenstore entries. xenbus_dev_changed() handles this case, and triggers device cleanup. It's possible that toolstack manages to connect new device in that place, before xenbus_dev_changed() notices the old one is missing. If that happens, new one won't be probed and will forever remain in XenbusStateInitialising. Fix this by checking the frontend's state in Xenstore. In case it has been reset to XenbusStateInitialising by Xen tools, consider this being the result of an unplug+plug operation. It's important that cleanup on such unplug doesn't modify Xenstore entries (especially the "state" key) as it belong to the new device to be probed - changing it would derail establishing connection to the new backend (most likely, closing the device before it was even connected). Handle this case by setting new xenbus_device->vanished flag to true, and check it before changing state entry. And even if xenbus_dev_changed() correctly detects the device was forcefully removed, the cleanup handling is still racy. Since this whole handling doesn't happened in a single Xenstore transaction, it's possible that toolstack might put a new device there already. Avoid re-creating the state key (which in the case of loosing the race would actually close newly attached device). The problem does not apply to frontend domain crash, as this case involves coordinated cleanup. Problem originally reported at https://lore.kernel.org/xen-devel/aOZvivyZ9YhVWDLN@mail-itl/T/#t, including reproduction steps. Based-on-patch-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20260218095205.453657-3-jgross@suse.com> 
When the backend domain crashes, coordinated device cleanup is not
possible (as it involves waiting for the backend state change). In that
case, toolstack forcefully removes frontend xenstore entries.
xenbus_dev_changed() handles this case, and triggers device cleanup.
It's possible that toolstack manages to connect new device in that
place, before xenbus_dev_changed() notices the old one is missing. If
that happens, new one won't be probed and will forever remain in
XenbusStateInitialising.

Fix this by checking the frontend's state in Xenstore. In case it has
been reset to XenbusStateInitialising by Xen tools, consider this
being the result of an unplug+plug operation.

It's important that cleanup on such unplug doesn't modify Xenstore
entries (especially the "state" key) as it belong to the new device
to be probed - changing it would derail establishing connection to the
new backend (most likely, closing the device before it was even
connected). Handle this case by setting new xenbus_device->vanished
flag to true, and check it before changing state entry.

And even if xenbus_dev_changed() correctly detects the device was
forcefully removed, the cleanup handling is still racy. Since this whole
handling doesn't happened in a single Xenstore transaction, it's possible
that toolstack might put a new device there already. Avoid re-creating
the state key (which in the case of loosing the race would actually
close newly attached device).

The problem does not apply to frontend domain crash, as this case
involves coordinated cleanup.

Problem originally reported at
https://lore.kernel.org/xen-devel/aOZvivyZ9YhVWDLN@mail-itl/T/#t,
including reproduction steps.

Based-on-patch-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260218095205.453657-3-jgross@suse.com>
xenbus: add xenbus_device parameter to xenbus_read_driver_state() 2026-03-04T14:31:40+00:00 Juergen Gross jgross@suse.com 2026-02-18T09:52:04+00:00 82169dace41cbaa951341b0f80f4570be3b2dec0 In order to prepare checking the xenbus device status in xenbus_read_driver_state(), add the pointer to struct xenbus_device as a parameter. Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Signed-off-by: Juergen Gross <jgross@suse.com> Acked-by: "Martin K. Petersen" <martin.petersen@oracle.com> # SCSI Acked-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Bjorn Helgaas <bhelgaas@google.com> # drivers/pci/xen-pcifront.c Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20260218095205.453657-2-jgross@suse.com> 
In order to prepare checking the xenbus device status in
xenbus_read_driver_state(), add the pointer to struct xenbus_device
as a parameter.

Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: "Martin K. Petersen" <martin.petersen@oracle.com> # SCSI
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>	# drivers/pci/xen-pcifront.c
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260218095205.453657-2-jgross@suse.com>
Partial revert "x86/xen: fix balloon target initialization for PVH dom0" 2026-02-02T06:31:22+00:00 Roger Pau Monne roger.pau@citrix.com 2026-01-28T11:05:08+00:00 0949c646d64697428ff6257d52efa5093566868d This partially reverts commit 87af633689ce16ddb166c80f32b120e50b1295de so the current memory target for PV guests is still fetched from start_info->nr_pages, which matches exactly what the toolstack sets the initial memory target to. Using get_num_physpages() is possible on PV also, but needs adjusting to take into account the ISA hole and the PFN at 0 not considered usable memory despite being populated, and hence would need extra adjustments. Instead of carrying those extra adjustments switch back to the previous code. That leaves Linux with a difference in how current memory target is obtained for HVM vs PV, but that's better than adding extra logic just for PV. However if switching to start_info->nr_pages for PV domains we need to differentiate between released pages (freed back to the hypervisor) as opposed to pages in the physmap which are not populated to start with. Introduce a new xen_unpopulated_pages to account for papges that have never been populated, and hence in the PV case don't need subtracting. Fixes: 87af633689ce ("x86/xen: fix balloon target initialization for PVH dom0") Reported-by: James Dingwall <james@dingwall.me.uk> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20260128110510.46425-2-roger.pau@citrix.com> 
This partially reverts commit 87af633689ce16ddb166c80f32b120e50b1295de so
the current memory target for PV guests is still fetched from
start_info->nr_pages, which matches exactly what the toolstack sets the
initial memory target to.

Using get_num_physpages() is possible on PV also, but needs adjusting to
take into account the ISA hole and the PFN at 0 not considered usable
memory despite being populated, and hence would need extra adjustments.
Instead of carrying those extra adjustments switch back to the previous
code.  That leaves Linux with a difference in how current memory target is
obtained for HVM vs PV, but that's better than adding extra logic just for
PV.

However if switching to start_info->nr_pages for PV domains we need to
differentiate between released pages (freed back to the hypervisor) as
opposed to pages in the physmap which are not populated to start with.
Introduce a new xen_unpopulated_pages to account for papges that have
never been populated, and hence in the PV case don't need subtracting.

Fixes: 87af633689ce ("x86/xen: fix balloon target initialization for PVH dom0")
Reported-by: James Dingwall <james@dingwall.me.uk>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260128110510.46425-2-roger.pau@citrix.com>
drivers/xen/xenbus: Replace deprecated strcpy in xenbus_transaction_end 2025-11-17T07:48:40+00:00 Thorsten Blum thorsten.blum@linux.dev 2025-10-31T11:21:31+00:00 a73d4a055622d0973e371382b16a13f9795ffec7 strcpy() is deprecated; inline the read-only string instead. Fix the function comment and use bool instead of int while we're at it. Link: https://github.com/KSPP/linux/issues/88 Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20251031112145.103257-2-thorsten.blum@linux.dev> 
strcpy() is deprecated; inline the read-only string instead. Fix the
function comment and use bool instead of int while we're at it.

Link: https://github.com/KSPP/linux/issues/88
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20251031112145.103257-2-thorsten.blum@linux.dev>
xen: replace XENFEAT_auto_translated_physmap with xen_pv_domain() 2025-09-08T15:01:36+00:00 Juergen Gross jgross@suse.com 2025-08-26T14:56:07+00:00 0f4283123fe1e6016296048d0fdcfce615047a13 Instead of testing the XENFEAT_auto_translated_physmap feature, just use !xen_pv_domain() which is equivalent. This has the advantage that a kernel not built with CONFIG_XEN_PV will be smaller due to dead code elimination. Reviewed-by: Jason Andryuk <jason.andryuk@amd.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20250826145608.10352-3-jgross@suse.com> 
Instead of testing the XENFEAT_auto_translated_physmap feature, just
use !xen_pv_domain() which is equivalent.

This has the advantage that a kernel not built with CONFIG_XEN_PV
will be smaller due to dead code elimination.

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250826145608.10352-3-jgross@suse.com>
xen: rework xen_pv_domain() 2025-09-08T15:01:36+00:00 Juergen Gross jgross@suse.com 2025-08-26T14:56:06+00:00 34c605fe53d49886d2741223b12950a33bdf2acf Rework xen_pv_domain() to no longer use the xen_domain_type variable, but the artificial X86_FEATURE_XENPV cpu feature. On non-x86 architectures xen_pv_domain() can be defined as "0". This has the advantage that a kernel not built with CONFIG_XEN_PV will be smaller due to dead code elimination. Set the X86_FEATURE_XENPV feature very early, as xen_pv_domain() is used rather early, too. Reviewed-by: Jason Andryuk <jason.andryuk@amd.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20250826145608.10352-2-jgross@suse.com> 
Rework xen_pv_domain() to no longer use the xen_domain_type variable,
but the artificial X86_FEATURE_XENPV cpu feature.

On non-x86 architectures xen_pv_domain() can be defined as "0".

This has the advantage that a kernel not built with CONFIG_XEN_PV
will be smaller due to dead code elimination.

Set the X86_FEATURE_XENPV feature very early, as xen_pv_domain() is
used rather early, too.

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250826145608.10352-2-jgross@suse.com>
Merge tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 2025-08-03T23:23:09+00:00 Linus Torvalds torvalds@linux-foundation.org 2025-08-03T23:23:09+00:00 e991acf1bce7a428794514cbbe216973c9c0a3c8 Pull non-MM updates from Andrew Morton: "Significant patch series in this pull request: - "squashfs: Remove page->mapping references" (Matthew Wilcox) gets us closer to being able to remove page->mapping - "relayfs: misc changes" (Jason Xing) does some maintenance and minor feature addition work in relayfs - "kdump: crashkernel reservation from CMA" (Jiri Bohac) switches us from static preallocation of the kdump crashkernel's working memory over to dynamic allocation. So the difficulty of a-priori estimation of the second kernel's needs is removed and the first kernel obtains extra memory - "generalize panic_print's dump function to be used by other kernel parts" (Feng Tang) implements some consolidation and rationalization of the various ways in which a failing kernel splats information at the operator * tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (80 commits) tools/getdelays: add backward compatibility for taskstats version kho: add test for kexec handover delaytop: enhance error logging and add PSI feature description samples: Kconfig: fix spelling mistake "instancess" -> "instances" fat: fix too many log in fat_chain_add() scripts/spelling.txt: add notifer||notifier to spelling.txt xen/xenbus: fix typo "notifer" net: mvneta: fix typo "notifer" drm/xe: fix typo "notifer" cxl: mce: fix typo "notifer" KVM: x86: fix typo "notifer" MAINTAINERS: add maintainers for delaytop ucount: use atomic_long_try_cmpxchg() in atomic_long_inc_below() ucount: fix atomic_long_inc_below() argument type kexec: enable CMA based contiguous allocation stackdepot: make max number of pools boot-time configurable lib/xxhash: remove unused functions init/Kconfig: restore CONFIG_BROKEN help text lib/raid6: update recov_rvv.c zero page usage docs: update docs after introducing delaytop ... 
Pull non-MM updates from Andrew Morton:
 "Significant patch series in this pull request:

   - "squashfs: Remove page->mapping references" (Matthew Wilcox) gets
     us closer to being able to remove page->mapping

   - "relayfs: misc changes" (Jason Xing) does some maintenance and
     minor feature addition work in relayfs

   - "kdump: crashkernel reservation from CMA" (Jiri Bohac) switches
     us from static preallocation of the kdump crashkernel's working
     memory over to dynamic allocation. So the difficulty of a-priori
     estimation of the second kernel's needs is removed and the first
     kernel obtains extra memory

   - "generalize panic_print's dump function to be used by other
     kernel parts" (Feng Tang) implements some consolidation and
     rationalization of the various ways in which a failing kernel
     splats information at the operator

* tag 'mm-nonmm-stable-2025-08-03-12-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (80 commits)
  tools/getdelays: add backward compatibility for taskstats version
  kho: add test for kexec handover
  delaytop: enhance error logging and add PSI feature description
  samples: Kconfig: fix spelling mistake "instancess" -> "instances"
  fat: fix too many log in fat_chain_add()
  scripts/spelling.txt: add notifer||notifier to spelling.txt
  xen/xenbus: fix typo "notifer"
  net: mvneta: fix typo "notifer"
  drm/xe: fix typo "notifer"
  cxl: mce: fix typo "notifer"
  KVM: x86: fix typo "notifer"
  MAINTAINERS: add maintainers for delaytop
  ucount: use atomic_long_try_cmpxchg() in atomic_long_inc_below()
  ucount: fix atomic_long_inc_below() argument type
  kexec: enable CMA based contiguous allocation
  stackdepot: make max number of pools boot-time configurable
  lib/xxhash: remove unused functions
  init/Kconfig: restore CONFIG_BROKEN help text
  lib/raid6: update recov_rvv.c zero page usage
  docs: update docs after introducing delaytop
  ...
xen/xenbus: fix typo "notifer" 2025-08-02T19:01:40+00:00 WangYuli wangyuli@uniontech.com 2025-07-22T07:34:30+00:00 004f42dd90b7ef542a51983bdaa5b2ef621ed41d There is a spelling mistake of 'notifer' in the comment which should be 'notifier'. Link: https://lkml.kernel.org/r/C6633C66376C709A+20250722073431.21983-7-wangyuli@uniontech.com Signed-off-by: WangYuli <wangyuli@uniontech.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> 
There is a spelling mistake of 'notifer' in the comment which
should be 'notifier'.

Link: https://lkml.kernel.org/r/C6633C66376C709A+20250722073431.21983-7-wangyuli@uniontech.com
Signed-off-by: WangYuli <wangyuli@uniontech.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
xen: Remove some deadcode (x) 2025-07-14T07:55:52+00:00 Dr. David Alan Gilbert linux@treblig.org 2025-07-13T13:26:25+00:00 0df11950099887520cc8bf22a790a5535be30e8d Remove three uncalled functions: xenbus_mkdir() was added in 2007 by commit 4bac07c993d0 ("xen: add the Xenbus sysfs and virtual device hotplug driver") but has remained unused. xen_get_runstate_snapshot() last use was removed in 2016 by commit 6ba286ad8457 ("xen: support runqueue steal time on xen") which replaces the use by the _cpu version. xen_resume_notifier_unregister() last use was removed in 2017 by commit 1914f0cd203c ("xen/acpi: upload PM state from init-domain to Xen") Remove them. Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com> Message-ID: <20250713132625.164728-1-linux@treblig.org> 
Remove three uncalled functions:

  xenbus_mkdir() was added in 2007 by
commit 4bac07c993d0 ("xen: add the Xenbus sysfs and virtual device hotplug
driver")
but has remained unused.

  xen_get_runstate_snapshot() last use was removed in 2016 by
commit 6ba286ad8457 ("xen: support runqueue steal time on xen")
which replaces the use by the _cpu version.

  xen_resume_notifier_unregister() last use was removed in 2017 by
commit 1914f0cd203c ("xen/acpi: upload PM state from init-domain to Xen")

Remove them.

Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250713132625.164728-1-linux@treblig.org>
xen/mcelog: Add __nonstring annotations for unterminated strings 2025-03-14T10:15:16+00:00 Kees Cook kees@kernel.org 2025-03-10T22:22:38+00:00 1c3dfc7c6b0f551fdca3f7c1f1e4c73be8adb17d When a character array without a terminating NUL character has a static initializer, GCC 15's -Wunterminated-string-initialization will only warn if the array lacks the "nonstring" attribute[1]. Mark the arrays with __nonstring to and correctly identify the char array as "not a C string" and thereby eliminate the warning. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1] Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Cc: xen-devel@lists.xenproject.org Signed-off-by: Kees Cook <kees@kernel.org> Acked-by: Juergen Gross <jgross@suse.com> Message-ID: <20250310222234.work.473-kees@kernel.org> Signed-off-by: Juergen Gross <jgross@suse.com> 
When a character array without a terminating NUL character has a static
initializer, GCC 15's -Wunterminated-string-initialization will only
warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
with __nonstring to and correctly identify the char array as "not a C
string" and thereby eliminate the warning.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Kees Cook <kees@kernel.org>
Acked-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250310222234.work.473-kees@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>