The 'read_reply' works with 'process_msg' to read of a reply in XenBus.
'process_msg' is running from within the 'xenbus' thread. Whenever
a message shows up in XenBus it is put on a xs_state.reply_list list
and 'read_reply' picks it up.
The problem is if the backend domain or the xenstored process is killed.
In which case 'xenbus' is still awaiting - and 'read_reply' if called -
stuck forever waiting for the reply_list to have some contents.
This is normally not a problem - as the backend domain can come back
or the xenstored process can be restarted. However if the domain
is in process of being powered off/restarted/halted - there is no
point of waiting on it coming back - as we are effectively being
terminated and should not impede the progress.
This patch solves this problem by checking whether the guest is the
right domain. If it is an initial domain and hurtling towards death -
there is no point of continuing the wait. All other type of guests
continue with their behavior (as Xenstore is expected to still be
running in another domain).
Fixes-Bug: http://bugs.xenproject.org/xen/bug/8
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Convert printks to pr_<level> (excludes printk(KERN_DEBUG...)
to be more consistent throughout the xen subsystem.
Add pr_fmt with KBUILD_MODNAME or "xen:" KBUILD_MODNAME
Coalesce formats and add missing word spaces
Add missing newlines
Align arguments and reflow to 80 columns
Remove DRV_NAME from formats as pr_fmt adds the same content
This does change some of the prefixes of these messages
but it also does make them more consistent.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
asm/xen/hypervisor.h was included twice.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This breaks on ARM. This quirk is not necessary on ARM because no
hypervisors of that vintage exist for that architecture (port is too
new).
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
[v1: Moved the ifdef inside the function per Jan Beulich suggestion]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
We were missing the 'void' on the parameter arguments.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
The commit 254d1a3f02, titled
"xen/pv-on-hvm kexec: shutdown watches from old kernel" assumes that the
XenBus backend can deal with reading of values from:
"control/platform-feature-xs_reset_watches":
... a patch for xenstored is required so that it
accepts the XS_RESET_WATCHES request from a client (see changeset
23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
the registration of watches will fail and some features of a PVonHVM
guest are not available. The guest is still able to boot, but repeated
kexec boots will fail."
Sadly this is not true when using a Xen 3.4 hypervisor and booting a PVHVM
guest. We end up hanging at:
err = xenbus_scanf(XBT_NIL, "control",
"platform-feature-xs_reset_watches", "%d", &supported);
This can easily be seen with guests hanging at xenbus_init:
NX (Execute Disable) protection: active
SMBIOS 2.4 present.
DMI: Xen HVM domU, BIOS 3.4.0 05/13/2011
Hypervisor detected: Xen HVM
Xen version 3.4.
Xen Platform PCI: I/O protocol version 1
... snip ..
calling xenbus_init+0x0/0x27e @ 1
Reverting the commit or using the attached patch fixes the issue. This fix
checks whether the hypervisor is older than 4.0 and if so does not try to
perform the read.
Fixes-Oracle-Bug: 14708233
CC: stable@vger.kernel.org
Acked-by: Olaf Hering <olaf@aepfle.de>
[v2: Added a comment in the source code]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
bind_evtchn_to_irqhandler can legitimately return 0 (irq 0): it is not
an error.
If Linux is running as an HVM domain and is running as Dom0, use
xenstored_local_init to initialize the xenstore page and event channel.
Changes in v4:
- do not xs_reset_watches on dom0.
Changes in v2:
- refactor xenbus_init.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
[v5: Fixed case switch indentations]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Add xs_reset_watches function to shutdown watches from old kernel after
kexec boot. The old kernel does not unregister all watches in the
shutdown path. They are still active, the double registration can not
be detected by the new kernel. When the watches fire, unexpected events
will arrive and the xenwatch thread will crash (jumps to NULL). An
orderly reboot of a hvm guest will destroy the entire guest with all its
resources (including the watches) before it is rebuilt from scratch, so
the missing unregister is not an issue in that case.
With this change the xenstored is instructed to wipe all active watches
for the guest. However, a patch for xenstored is required so that it
accepts the XS_RESET_WATCHES request from a client (see changeset
23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
the registration of watches will fail and some features of a PVonHVM
guest are not available. The guest is still able to boot, but repeated
kexec boots will fail.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
* 'stable/for-linus-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen: (37 commits)
xen/pciback: Expand the warning message to include domain id.
xen/pciback: Fix "device has been assigned to X domain!" warning
xen/pciback: Move the PCI_DEV_FLAGS_ASSIGNED ops to the "[un|]bind"
xen/xenbus: don't reimplement kvasprintf via a fixed size buffer
xenbus: maximum buffer size is XENSTORE_PAYLOAD_MAX
xen/xenbus: Reject replies with payload > XENSTORE_PAYLOAD_MAX.
Xen: consolidate and simplify struct xenbus_driver instantiation
xen-gntalloc: introduce missing kfree
xen/xenbus: Fix compile error - missing header for xen_initial_domain()
xen/netback: Enable netback on HVM guests
xen/grant-table: Support mappings required by blkback
xenbus: Use grant-table wrapper functions
xenbus: Support HVM backends
xen/xenbus-frontend: Fix compile error with randconfig
xen/xenbus-frontend: Make error message more clear
xen/privcmd: Remove unused support for arch specific privcmp mmap
xen: Add xenbus_backend device
xen: Add xenbus device driver
xen: Add privcmd device driver
xen/gntalloc: fix reference counts on multi-page mappings
...
Haogang Chen found out that:
There is a potential integer overflow in process_msg() that could result
in cross-domain attack.
body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);
When a malicious guest passes 0xffffffff in msg->hdr.len, the subsequent
call to xb_read() would write to a zero-length buffer.
The other end of this connection is always the xenstore backend daemon
so there is no guest (malicious or otherwise) which can do this. The
xenstore daemon is a trusted component in the system.
However this seem like a reasonable robustness improvement so we should
have it.
And Ian when read the API docs found that:
The payload length (len field of the header) is limited to 4096
(XENSTORE_PAYLOAD_MAX) in both directions. If a client exceeds the
limit, its xenstored connection will be immediately killed by
xenstored, which is usually catastrophic from the client's point of
view. Clients (particularly domains, which cannot just reconnect)
should avoid this.
so this patch checks against that instead.
This also avoids a potential integer overflow pointed out by Haogang Chen.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Haogang Chen <haogangchen@gmail.com>
CC: stable@kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This reverts commit ddacf5ef68.
As when booting the kernel under Amazon EC2 as an HVM guest it ends up
hanging during startup. Reverting this we loose the fix for kexec
booting to the crash kernels.
Fixes Canonical BZ #901305 (http://bugs.launchpad.net/bugs/901305)
Tested-by: Alessandro Salvatori <sandr8@gmail.com>
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Randy found a compile error when using make randconfig to trigger
drivers/xen/xenbus/xenbus_xs.c:909:2: error: implicit declaration of function 'xen_hvm_domain'
it is unclear which of the CONFIG options triggered this. This
patch fixes the error.
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Add new xs_reset_watches function to shutdown watches from old kernel after
kexec boot. The old kernel does not unregister all watches in the
shutdown path. They are still active, the double registration can not
be detected by the new kernel. When the watches fire, unexpected events
will arrive and the xenwatch thread will crash (jumps to NULL). An
orderly reboot of a hvm guest will destroy the entire guest with all its
resources (including the watches) before it is rebuilt from scratch, so
the missing unregister is not an issue in that case.
With this change the xenstored is instructed to wipe all active watches
for the guest. However, a patch for xenstored is required so that it
accepts the XS_RESET_WATCHES request from a client (see changeset
23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
the registration of watches will fail and some features of a PVonHVM
guest are not available. The guest is still able to boot, but repeated
kexec boots will fail.
[v5: use xs_single instead of passing a dummy string to xs_talkv]
[v4: ignore -EEXIST in xs_reset_watches]
[v3: use XS_RESET_WATCHES instead of XS_INTRODUCE]
[v2: move all code which deals with XS_INTRODUCE into xs_introduce()
(based on feedback from Ian Campbell); remove casts from kvec assignment]
Signed-off-by: Olaf Hering <olaf@aepfle.de>
[v1: Redid the git description a bit]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
During repeated kexec boots xenwatch_thread() can crash because
xenbus_watch->callback is cleared by xenbus_watch_path() if a node/token
combo for a new watch happens to match an already registered watch from
an old kernel. In this case xs_watch returns -EEXISTS, then
register_xenbus_watch() does not remove the to-be-registered watch from
the list of active watches but returns the -EEXISTS to the caller
anyway.
Because the watch is still active in xenstored it will cause an event
which will arrive in the new kernel. process_msg() will find the
encapsulated struct xenbus_watch in its list of registered watches and
puts the "empty" watch handle in the queue for xenwatch_thread().
xenwatch_thread() then calls ->callback which was cleared earlier by
xenbus_watch_path().
To prevent that crash in a guest running on an old xen toolstack remove
the special -EEXIST handling.
v2:
- remove the EEXIST handing in register_xenbus_watch() instead of
checking for ->callback in process_msg()
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Since the device we are resuming could be the device containing the
swap device we should ensure that the allocation cannot cause
IO.
On resume, this path is triggered when the running system tries to
continue using its devices. If it cannot then the resume will fail;
to try to avoid this we let it dip into the emergency pools.
The majority of these changes were made when linux-2.6.18-xen.hg
changeset e8b49cfbdac0 was ported upstream in
a144ff09bc but somehow this hunk was
dropped.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Stable Kernel <stable@kernel.org> # .32.x
================================================
[ BUG: lock held when returning to user space! ]
------------------------------------------------
xenstore-list/3522 is leaving the kernel with locks still held!
1 lock held by xenstore-list/3522:
#0: (&xs_state.transaction_mutex){......}, at: [<c026dc6f>] xenbus_dev_request_and_reply+0x8f/0xa0
The canonical fix for this type of issue appears to be to maintain a
count manually rather than using an rwsem so do that here.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
The xenfs filesystem exports various interfaces to usermode. Initially
this exports a file to allow usermode to interact with xenbus/xenstore.
Traditionally this appeared in /proc/xen. Rather than extending procfs,
this patch adds a backward-compat mountpoint on /proc/xen, and provides
a xenfs filesystem which can be mounted there.
Signed-off-by: Alex Zeffertt <alex.zeffertt@eu.citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Avoid allocations causing swap activity on the resume path by
preventing the allocations from doing IO and allowing them
to access the emergency pools.
These paths are used when a frontend device is trying to connect
to its backend driver over Xenbus. These reconnections are triggered
on demand by IO, so by definition there is already IO underway,
and further IO would naturally deadlock. On resume, this path
is triggered when the running system tries to continue using its
devices. If it cannot then the resume will fail; to try to avoid this
we let it dip into the emergency pools.
[ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ]
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch fixes an obvious use-after-free spotted by the Coverity checker.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This communicates with the machine control software via a registry
residing in a controlling virtual machine. This allows dynamic
creation, destruction and modification of virtual device
configurations (network devices, block devices and CPUS, to name some
examples).
[ Greg, would you mind giving this a review? Thanks -J ]
Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Greg KH <greg@kroah.com>
Konrad Rzeszutek Wilk