Commits on May 22, 2023

1. hw/pci: Disable PCI_ERR_UNCOR_MASK register for machine type < 8.0 …

   Since it's implementation on v8.0.0-rc0, having the PCI_ERR_UNCOR_MASK
   set for machine types < 8.0 will cause migration to fail if the target
   QEMU version is < 8.0.0 :
   
   qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x10a read: 40 device: 0 cmask: ff wmask: 0 w1cmask:0
   qemu-system-x86_64: Failed to load PCIDevice:config
   qemu-system-x86_64: Failed to load e1000e:parent_obj
   qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:02.0/e1000e'
   qemu-system-x86_64: load of migration failed: Invalid argument
   
   The above test migrated a 7.2 machine type from QEMU master to QEMU 7.2.0,
   with this cmdline:
   
   ./qemu-system-x86_64 -M pc-q35-7.2 [-incoming XXX]
   
   In order to fix this, property x-pcie-err-unc-mask was introduced to
   control when PCI_ERR_UNCOR_MASK is enabled. This property is enabled by
   default, but is disabled if machine type <= 7.2.
   
   Fixes: 010746a ("hw/pci/aer: Implement PCI_ERR_UNCOR_MASK register")
   Suggested-by: Michael S. Tsirkin <mst@redhat.com>
   Signed-off-by: Leonardo Bras <leobras@redhat.com>
   Message-Id: <20230503002701.854329-1-leobras@redhat.com>
   Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
   Reviewed-by: Peter Xu <peterx@redhat.com>
   Reviewed-by: Juan Quintela <quintela@redhat.com>
   Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1576
   Tested-by: Fiona Ebner <f.ebner@proxmox.com>
   Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
   Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
   (cherry picked from commit 5ed3dab)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Leonardo Bras authored and Michael Tokarev committed May 22, 2023
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2. virtio-net: not enable vq reset feature unconditionally …

   The commit 93a97dc ("virtio-net: enable vq reset feature") enables
   unconditionally vq reset feature as long as the device is emulated.
   This makes impossible to actually disable the feature, and it causes
   migration problems from qemu version previous than 7.2.
   
   The entire final commit is unneeded as device system already enable or
   disable the feature properly.
   
   This reverts commit 93a97dc.
   Fixes: 93a97dc ("virtio-net: enable vq reset feature")
   Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
   
   Message-Id: <20230504101447.389398-1-eperezma@redhat.com>
   Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
   Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
   Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
   (cherry picked from commit 1fac00f)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   

   eugpermar authored and Michael Tokarev committed May 22, 2023
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3. virtio-crypto: fix NULL pointer dereference in virtio_crypto_free_req… …

   …uest
   
   Ensure op_info is not NULL in case of QCRYPTODEV_BACKEND_ALG_SYM algtype.
   
   Fixes: 0e660a6 ("crypto: Introduce RSA algorithm")
   Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
   Reported-by: Yiming Tao <taoym@zju.edu.cn>
   Message-Id: <20230509075317.1132301-1-mcascell@redhat.com>
   Reviewed-by: Gonglei <arei.gonglei@huawei.com>
   Reviewed-by: zhenwei pi<pizhenwei@bytedance.com>
   Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
   Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
   (cherry picked from commit 3e69908)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Mauro Matteo Cascella authored and Michael Tokarev committed May 22, 2023
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4. aio-posix: do not nest poll handlers …

   QEMU's event loop supports nesting, which means that event handler
   functions may themselves call aio_poll(). The condition that triggered a
   handler must be reset before the nested aio_poll() call, otherwise the
   same handler will be called and immediately re-enter aio_poll. This
   leads to an infinite loop and stack exhaustion.
   
   Poll handlers are especially prone to this issue, because they typically
   reset their condition by finishing the processing of pending work.
   Unfortunately it is during the processing of pending work that nested
   aio_poll() calls typically occur and the condition has not yet been
   reset.
   
   Disable a poll handler during ->io_poll_ready() so that a nested
   aio_poll() call cannot invoke ->io_poll_ready() again. As a result, the
   disabled poll handler and its associated fd handler do not run during
   the nested aio_poll(). Calling aio_set_fd_handler() from inside nested
   aio_poll() could cause it to run again. If the fd handler is pending
   inside nested aio_poll(), then it will also run again.
   
   In theory fd handlers can be affected by the same issue, but they are
   more likely to reset the condition before calling nested aio_poll().
   
   This is a special case and it's somewhat complex, but I don't see a way
   around it as long as nested aio_poll() is supported.
   
   Cc: qemu-stable@nongnu.org
   Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2186181
   Fixes: c382706 ("block: Mark bdrv_co_io_(un)plug() and callers GRAPH_RDLOCK")
   Cc: Kevin Wolf <kwolf@redhat.com>
   Cc: Emanuele Giuseppe Esposito <eesposit@redhat.com>
   Cc: Paolo Bonzini <pbonzini@redhat.com>
   Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
   Message-Id: <20230502184134.534703-2-stefanha@redhat.com>
   Reviewed-by: Kevin Wolf <kwolf@redhat.com>
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   (cherry picked from commit 6d740fb)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Stefan Hajnoczi authored and Michael Tokarev committed May 22, 2023
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5. tested: add test for nested aio_poll() in poll handlers …

   Cc: qemu-stable@nongnu.org
   Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
   Message-Id: <20230502184134.534703-3-stefanha@redhat.com>
   [kwolf: Restrict to CONFIG_POSIX, Windows doesn't support polling]
   Tested-by: Kevin Wolf <kwolf@redhat.com>
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   (cherry picked from commit 844a12a)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Stefan Hajnoczi authored and Michael Tokarev committed May 22, 2023
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6. block: compile out assert_bdrv_graph_readable() by default …

   reader_count() is a performance bottleneck because the global
   aio_context_list_lock mutex causes thread contention. Put this debugging
   assertion behind a new ./configure --enable-debug-graph-lock option and
   disable it by default.
   
   The --enable-debug-graph-lock option is also enabled by the more general
   --enable-debug option.
   
   Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
   Message-Id: <20230501173443.153062-1-stefanha@redhat.com>
   Reviewed-by: Kevin Wolf <kwolf@redhat.com>
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   (cherry picked from commit 58a2e3f)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Stefan Hajnoczi authored and Michael Tokarev committed May 22, 2023
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7. graph-lock: Disable locking for now …

   In QEMU 8.0, we've been seeing deadlocks in bdrv_graph_wrlock(). They
   come from callers that hold an AioContext lock, which is not allowed
   during polling. In theory, we could temporarily release the lock, but
   callers are inconsistent about whether they hold a lock, and if they do,
   some are also confused about which one they hold. While all of this is
   fixable, it's not trivial, and the best course of action for 8.0.1 is
   probably just disabling the graph locking code temporarily.
   
   We don't currently rely on graph locking yet. It is supposed to replace
   the AioContext lock eventually to enable multiqueue support, but as long
   as we still have the AioContext lock, it is sufficient without the graph
   lock. Once the AioContext lock goes away, the deadlock doesn't exist any
   more either and this commit can be reverted. (Of course, it can also be
   reverted while the AioContext lock still exists if the callers have been
   fixed.)
   
   Cc: qemu-stable@nongnu.org
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   Message-Id: <20230517152834.277483-2-kwolf@redhat.com>
   Reviewed-by: Eric Blake <eblake@redhat.com>
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   (cherry picked from commit 80fc5d2)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Kevin Wolf authored and Michael Tokarev committed May 22, 2023
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8. nbd/server: Fix drained_poll to wake coroutine in right AioContext …

   nbd_drained_poll() generally runs in the main thread, not whatever
   iothread the NBD server coroutine is meant to run in, so it can't
   directly reenter the coroutines to wake them up.
   
   The code seems to have the right intention, it specifies the correct
   AioContext when it calls qemu_aio_coroutine_enter(). However, this
   functions doesn't schedule the coroutine to run in that AioContext, but
   it assumes it is already called in the home thread of the AioContext.
   
   To fix this, add a new thread-safe qio_channel_wake_read() that can be
   called in the main thread to wake up the coroutine in its AioContext,
   and use this in nbd_drained_poll().
   
   Cc: qemu-stable@nongnu.org
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   Message-Id: <20230517152834.277483-3-kwolf@redhat.com>
   Reviewed-by: Eric Blake <eblake@redhat.com>
   Signed-off-by: Kevin Wolf <kwolf@redhat.com>
   (cherry picked from commit 7c1f51b)
   Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

   Kevin Wolf authored and Michael Tokarev committed May 22, 2023
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