* Re: [RFC patch 14/15] workpending: Provide infrastructure for work before entering a guest
[not found] ` <20190919150809.860645841@linutronix.de>
@ 2019-09-26 11:35 ` Miroslav Benes
0 siblings, 0 replies; only message in thread
From: Miroslav Benes @ 2019-09-26 11:35 UTC (permalink / raw)
To: Thomas Gleixner
Cc: LKML, x86, Peter Zijlstra, Andy Lutomirski, Catalin Marinas,
Will Deacon, Mark Rutland, Marc Zyngier, Paolo Bonzini, kvm,
linux-arch, live-patching
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
[...]
> +#define EXIT_TO_GUESTMODE_WORK \
> + (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_RESUME | \
> + ARCH_EXIT_TO_GUESTMODE_WORK)
[...]
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
>
> +int core_exit_to_guestmode_work(struct kvm *kvm, struct kvm_vcpu *vcpu,
> + unsigned long ti_work)
> +{
> + /*
> + * Before returning to guest mode handle all pending work
> + */
> + if (ti_work & _TIF_SIGPENDING) {
> + vcpu->run->exit_reason = KVM_EXIT_INTR;
> + vcpu->stat.signal_exits++;
> + return -EINTR;
> + }
> +
> + if (ti_work & _TIF_NEED_RESCHED) {
> + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + schedule();
> + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + }
> +
> + if (ti_work & _TIF_PATCH_PENDING) {
> + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + klp_update_patch_state(current);
> + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + }
If I am reading the code correctly, _TIF_PATCH_PENDING is not a part of
EXIT_TO_GUESTMODE_WORK, so the handling code here would not be called on
any arch as of now.
I also think that _TIF_PATCH_PENDING must not be handled here generally.
It could break consistency guarantees when live patching KVM (and we do
that from time to time).
Adding live-patching ML to CC.
Miroslav
> + if (ti_work & _TIF_NOTIFY_RESUME) {
> + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + clear_thread_flag(TIF_NOTIFY_RESUME);
> + tracehook_notify_resume(NULL);
> + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + }
> +
> + /* Any extra architecture specific work */
> + return arch_exit_to_guestmode_work(kvm, vcpu, ti_work);
> +}
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