Eduardo Habkost wrote:
This patch adds an interface to set a function to be called on crash time,
on each CPU. The function will be set by code that enables virtualization
extensions on the CPUs (i.e. KVM). It will be called once on each CPU
by machine_crash_shutdown(), and should do the very least to disable
virt extensions on the CPU where it is being called.
The function will be used by KVM to disable virtualization before halting
the CPUs, otherwise the booting of the kdump kernel may hang. It does
hang, when vmx is enabled, and I wouldn't be surprised if having svm
enabled also causes problems.
The functions that set the function pointer uses RCU synchronization,
just in case the crash NMI is triggered while KVM is unloading.
We can't just use the same notifiers used at reboot time (that are used
by non-crash-dump kexec), because at crash time some CPUs may have IRQs
disabled, so we can't use IPIs. The crash shutdown code use NMIs to
tell the other CPUs to be halted, so the notifier call is hooked into
the CPU halting code that is on the crash shutdown NMI handler.
+static void (*virt_disable_fn)(unsigned int cpu);
Since you never use the cpu argument, I suggest dropping it.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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