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vmbus_wait_for_unload() may be called in the panic path after other
CPUs are stopped. vmbus_wait_for_unload() currently loops through
online CPUs looking for the UNLOAD response message. But the values of
CONFIG_KEXEC_CORE and crash_kexec_post_notifiers affect the path used
to stop the other CPUs, and in one of the paths the stopped CPUs
are removed from cpu_online_mask. This removal happens in both
x86/x64 and arm64 architectures. In such a case, vmbus_wait_for_unload()
only checks the panic'ing CPU, and misses the UNLOAD response message
except when the panic'ing CPU is CPU 0. vmbus_wait_for_unload()
eventually times out, but only after waiting 100 seconds.
Fix this by looping through *present* CPUs in vmbus_wait_for_unload().
The cpu_present_mask is not modified by stopping the other CPUs in the
panic path, nor should it be.
Also, in a CoCo VM the synic_message_page is not allocated in
hv_synic_alloc(), but is set and cleared in hv_synic_enable_regs()
and hv_synic_disable_regs() such that it is set only when the CPU is
online. If not all present CPUs are online when vmbus_wait_for_unload()
is called, the synic_message_page might be NULL. Add a check for this.
Fixes: cd95aad557 ("Drivers: hv: vmbus: handle various crash scenarios")
Cc: stable@vger.kernel.org
Reported-by: John Starks <jostarks@microsoft.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/1684422832-38476-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.