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Sean Christopherson
d76fb40637
Move the posted interrupt pre/post_block logic into vcpu_put/load respectively, using the kvm_vcpu_is_blocking() to determining whether or not the wakeup handler needs to be set (and unset). This avoids updating the PI descriptor if halt-polling is successful, reduces the number of touchpoints for updating the descriptor, and eliminates the confusing behavior of intentionally leaving a "stale" PI.NDST when a blocking vCPU is scheduled back in after preemption. The downside is that KVM will do the PID update twice if the vCPU is preempted after prepare_to_rcuwait() but before schedule(), but that's a rare case (and non-existent on !PREEMPT kernels). The notable wart is the need to send a self-IPI on the wakeup vector if an outstanding notification is pending after configuring the wakeup vector. Ideally, KVM would just do a kvm_vcpu_wake_up() in this case, but the scheduler doesn't support waking a task from its preemption notifier callback, i.e. while the task is right in the middle of being scheduled out. Note, setting the wakeup vector before halt-polling is not necessary: once the pending IRQ will be recorded in the PIR, kvm_vcpu_has_events() will detect this (via kvm_cpu_get_interrupt(), kvm_apic_get_interrupt(), apic_has_interrupt_for_ppr() and finally vmx_sync_pir_to_irr()) and terminate the polling. Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20211208015236.1616697-5-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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.