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  1. 23 3月, 2016 20 次提交
  3. 22 3月, 2016 20 次提交
    • M
      contrib/ivshmem-server: Print "not for production" warning · a335c6f2
      由 Markus Armbruster 提交于 
      The code is okay for illustrating how things work and for testing, but
its error handling make it unfit for production use.  Print a warning
to protect the innocent.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-41-git-send-email-armbru@redhat.com>
      a335c6f2
    • M
      ivshmem: Require master to have ID zero · 62a830b6
      由 Markus Armbruster 提交于 
      Migration with ivshmem needs to be carefully orchestrated to work.
Exactly one peer (the "master") migrates to the destination, all other
peers need to unplug (and disconnect), migrate, plug back (and
reconnect).  This is sort of documented in qemu-doc.

If peers connect on the destination before migration completes, the
shared memory can get messed up.  This isn't documented anywhere.  Fix
that in qemu-doc.

To avoid messing up register IVPosition on migration, the server must
assign the same ID on source and destination.  ivshmem-spec.txt leaves
ID assignment unspecified, however.

Amend ivshmem-spec.txt to require the first client to receive ID zero.
The example ivshmem-server complies: it always assigns the first
unused ID.

For a bit of additional safety, enforce ID zero for the master.  This
does nothing when we're not using a server, because the ID is zero for
all peers then.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-40-git-send-email-armbru@redhat.com>
      62a830b6
    • M
      ivshmem: Drop ivshmem property x-memdev · 13fd2cb6
      由 Markus Armbruster 提交于 
      Use ivshmem-plain instead.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-39-git-send-email-armbru@redhat.com>
      13fd2cb6
    • M
      ivshmem: Clean up after the previous commit · ddc85284
      由 Markus Armbruster 提交于 
      Move code to more sensible places.  Use the opportunity to reorder and
document IVShmemState members.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-38-git-send-email-armbru@redhat.com>
      ddc85284
    • M
      ivshmem: Split ivshmem-plain, ivshmem-doorbell off ivshmem · 5400c02b
      由 Markus Armbruster 提交于 
      ivshmem can be configured with and without interrupt capability
(a.k.a. "doorbell").  The two configurations have largely disjoint
options, which makes for a confusing (and badly checked) user
interface.  Moreover, the device can't tell the guest whether its
doorbell is enabled.

Create two new device models ivshmem-plain and ivshmem-doorbell, and
deprecate the old one.

Changes from ivshmem:

* PCI revision is 1 instead of 0.  The new revision is fully backwards
  compatible for guests.  Guests may elect to require at least
  revision 1 to make sure they're not exposed to the funny "no shared
  memory, yet" state.

* Property "role" replaced by "master".  role=master becomes
  master=on, role=peer becomes master=off.  Default is off instead of
  auto.

* Property "use64" is gone.  The new devices always have 64 bit BARs.

Changes from ivshmem to ivshmem-plain:

* The Interrupt Pin register in PCI config space is zero (does not use
  an interrupt pin) instead of one (uses INTA).

* Property "x-memdev" is renamed to "memdev".

* Properties "shm" and "size" are gone.  Use property "memdev"
  instead.

* Property "msi" is gone.  The new device can't have MSI-X capability.
  It can't interrupt anyway.

* Properties "ioeventfd" and "vectors" are gone.  They're meaningless
  without interrupts anyway.

Changes from ivshmem to ivshmem-doorbell:

* Property "msi" is gone.  The new device always has MSI-X capability.

* Property "ioeventfd" defaults to on instead of off.

* Property "size" is gone.  The new device can only map all the shared
  memory received from the server.

Guests can easily find out whether the device is configured for
interrupts by checking for MSI-X capability.

Note: some code added in sub-optimal places to make the diff easier to
review.  The next commit will move it to more sensible places.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-37-git-send-email-armbru@redhat.com>
      5400c02b
    • M
      ivshmem: Replace int role_val by OnOffAuto master · 2a845da7
      由 Markus Armbruster 提交于 
      In preparation of making it a qdev property.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-36-git-send-email-armbru@redhat.com>
      2a845da7
    • M
      qdev: New DEFINE_PROP_ON_OFF_AUTO · 55e8a154
      由 Markus Armbruster 提交于 
      Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-35-git-send-email-armbru@redhat.com>
      55e8a154
    • M
      ivshmem: Inline check_shm_size() into its only caller · 8baeb22b
      由 Markus Armbruster 提交于 
      Improve the error messages while there.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <1458066895-20632-34-git-send-email-armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
      8baeb22b
    • M
      ivshmem: Simplify memory regions for BAR 2 (shared memory) · c2d8019c
      由 Markus Armbruster 提交于 
      ivshmem_realize() puts the shared memory region in a container region.
Used to be necessary to permit delayed mapping of the shared memory.
However, we recently moved to synchronous mapping, in "ivshmem:
Receive shared memory synchronously in realize()" and the commit
following it.  The container is redundant since then.  Drop it.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <1458066895-20632-33-git-send-email-armbru@redhat.com>
      c2d8019c
    • M
      ivshmem: Implement shm=... with a memory backend · 5503e285
      由 Markus Armbruster 提交于 
      ivshmem has its very own code to create and map shared memory.
Replace that with an implicitly created memory backend.  Reduces the
number of ways we create BAR 2 from three to two.

The memory-backend-file is currently available only with CONFIG_LINUX,
so this adds a second Linuxism to ivshmem (the other one is eventfd).
Should we ever need to make it portable to systems where
memory-backend-file can't be made to serve, we could create a
memory-backend-shmem that allocates memory with shm_open().

Bonus fix: shared memory files are now created with permissions 0655
instead of 0777.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <1458066895-20632-32-git-send-email-armbru@redhat.com>
      5503e285
    • M
      ivshmem: Tighten check of property "size" · 08183c20
      由 Markus Armbruster 提交于 
      If size_t is narrower than 64 bits, passing uint64_t ivshmem_size to
mmap() truncates.  Reject such sizes.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-31-git-send-email-armbru@redhat.com>
      08183c20
    • M
      ivshmem: Simplify how we cope with short reads from server · ee276391
      由 Markus Armbruster 提交于 
      Short reads from a UNIX domain sockets are exceedingly unlikely when
the other side always sends eight bytes and we always read eight
bytes.  We cope with them anyway.  However, the code doing that is
rather convoluted.  Dumb it down radically.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-30-git-send-email-armbru@redhat.com>
      ee276391
    • M
      ivshmem: Drop the hackish test for UNIX domain chardev · ba5970a1
      由 Markus Armbruster 提交于 
      The chardev must be capable of transmitting SCM_RIGHTS ancillary
messages.  We check it by comparing CharDriverState member filename to
"unix:".  That's almost as brittle as it is disgusting.

When the actual transmission all happened asynchronously, this check
was all we could do in realize(), and thus better than nothing.  But
now we receive at least one SCM_RIGHTS synchronously in realize(),
it's not worth its keep anymore.  Drop it.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-29-git-send-email-armbru@redhat.com>
      ba5970a1
    • M
      ivshmem: Rely on server sending the ID right after the version · a3feb086
      由 Markus Armbruster 提交于 
      The protocol specification (ivshmem-spec.txt, formerly
ivshmem_device_spec.txt) has always required the ID message to be sent
right at the beginning, and ivshmem-server has always complied.  The
device, however, accepts it out of order.  If an interrupt setup
arrived before it, though, it would be misinterpreted as connect
notification.  Fix the latent bug by relying on the spec and
ivshmem-server's actual behavior.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-28-git-send-email-armbru@redhat.com>
      a3feb086
    • M
      ivshmem: Propagate errors through ivshmem_recv_setup() · 1309cf44
      由 Markus Armbruster 提交于 
      This kills off the funny state described in the previous commit.

Simplify ivshmem_io_read() accordingly, and update documentation.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <1458066895-20632-27-git-send-email-armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
      1309cf44
    • M
      ivshmem: Receive shared memory synchronously in realize() · 3a55fc0f
      由 Markus Armbruster 提交于 
      When configured for interrupts (property "chardev" given), we receive
the shared memory from an ivshmem server.  We do so asynchronously
after realize() completes, by setting up callbacks with
qemu_chr_add_handlers().

Keeping server I/O out of realize() that way avoids delays due to a
slow server.  This is probably relevant only for hot plug.

However, this funny "no shared memory, yet" state of the device also
causes a raft of issues that are hard or impossible to work around:

* The guest is exposed to this state: when we enter and leave it its
  shared memory contents is apruptly replaced, and device register
  IVPosition changes.

  This is a known issue.  We document that guests should not access
  the shared memory after device initialization until the IVPosition
  register becomes non-negative.

  For cold plug, the funny state is unlikely to be visible in
  practice, because we normally receive the shared memory long before
  the guest gets around to mess with the device.

  For hot plug, the timing is tighter, but the relative slowness of
  PCI device configuration has a good chance to hide the funny state.

  In either case, guests complying with the documented procedure are
  safe.

* Migration becomes racy.

  If migration completes before the shared memory setup completes on
  the source, shared memory contents is silently lost.  Fortunately,
  migration is rather unlikely to win this race.

  If the shared memory's ramblock arrives at the destination before
  shared memory setup completes, migration fails.

  There is no known way for a management application to wait for
  shared memory setup to complete.

  All you can do is retry failed migration.  You can improve your
  chances by leaving more time between running the destination QEMU
  and the migrate command.

  To mitigate silent memory loss, you need to ensure the server
  initializes shared memory exactly the same on source and
  destination.

  These issues are entirely undocumented so far.

I'd expect the server to be almost always fast enough to hide these
issues.  But then rare catastrophic races are in a way the worst kind.

This is way more trouble than I'm willing to take from any device.
Kill the funny state by receiving shared memory synchronously in
realize().  If your hot plug hangs, go kill your ivshmem server.

For easier review, this commit only makes the receive synchronous, it
doesn't add the necessary error propagation.  Without that, the funny
state persists.  The next commit will do that, and kill it off for
real.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-26-git-send-email-armbru@redhat.com>
      3a55fc0f
    • M
      ivshmem: Plug leaks on unplug, fix peer disconnect · 9db51b4d
      由 Markus Armbruster 提交于 
      close_peer_eventfds() cleans up three things: ioeventfd triggers if
they exist, eventfds, and the array to store them.

Commit 98609cd8 (v1.2.0) fixed it not to clean up ioeventfd triggers
when they don't exist (property ioeventfd=off, which is the default).
Unfortunately, the fix also made it skip cleanup of the eventfds and
the array then.  This is a memory and file descriptor leak on unplug.

Additionally, the reset of nb_eventfds is skipped.  Doesn't matter on
unplug.  On peer disconnect, however, this permanently wedges the
interrupt vectors used for that peer's ID.  The eventfds stay behind,
but aren't connected to a peer anymore.  When the ID gets recycled for
a new peer, the new peer's eventfds get assigned to vectors after the
old ones.  Commonly, the device's number of vectors matches the
server's, so the new ones get dropped with a "Too many eventfd
received" message.  Interrupts either don't work (common case) or go
to the wrong vector.

Fix by narrowing the conditional to just the ioeventfd trigger
cleanup.

While there, move the "invalid" peer check to the only caller where it
can actually happen, and tighten it to reject own ID.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-25-git-send-email-armbru@redhat.com>
      9db51b4d
    • M
      ivshmem: Disentangle ivshmem_read() · ca0b7566
      由 Markus Armbruster 提交于 
      Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-24-git-send-email-armbru@redhat.com>
      ca0b7566
    • M
      ivshmem: Simplify rejection of invalid peer ID from server · cd9953f7
      由 Markus Armbruster 提交于 
      ivshmem_read() processes server messages.  These are 64 bit signed
integers.  -1 is shared memory setup, 16 bit unsigned is a peer ID,
anything else is invalid.

ivshmem_read() rejects invalid negative messages right away, silently.

Invalid positive messages get rejected only in resize_peers(), and
ivshmem_read() then prints the rather cryptic message "failed to
resize peers array".

Extend the first check to cover all invalid messages, make it report
"server sent invalid message", and drop the second check.

Now resize_peers() can't fail anymore; simplify.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-23-git-send-email-armbru@redhat.com>
      cd9953f7
    • M
      ivshmem: Assert interrupts are set up once · 3c27969b
      由 Markus Armbruster 提交于 
      An interrupt is set up when the interrupt's file descriptor is
received.  Each message applies to the next interrupt vector.
Therefore, each vector cannot be set up more than once.

ivshmem_add_kvm_msi_virq() half-heartedly tries not to rely on this by
doing nothing then, but that's not going to recover from this error
should it become possible in the future.  watch_vector_notifier()
doesn't even try.

Simply assert what is the case, so we get alerted if we ever screw it
up.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1458066895-20632-22-git-send-email-armbru@redhat.com>
      3c27969b