linux-kernel - Re: [RESEND PATCH ] KVM: VMX: Enable/disable PML when dirty logging gets enabled/disabled

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Date:   Wed, 10 Feb 2021 16:55:35 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Makarand Sonare <makarandsonare@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, pshier@...gle.com, jmattson@...gle.com,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [RESEND PATCH ] KVM: VMX: Enable/disable PML when dirty logging
 gets enabled/disabled

On Wed, Feb 10, 2021, Makarand Sonare wrote:
> @@ -7517,9 +7531,39 @@ static void vmx_slot_enable_log_dirty(struct kvm *kvm,
>  static void vmx_slot_disable_log_dirty(struct kvm *kvm,
>  				       struct kvm_memory_slot *slot)
>  {
> +	/*
> +	 * Check all slots and disable PML if dirty logging
> +	 * is being disabled for the last slot
> +	 *
> +	 */
> +	if (enable_pml &&
> +	    kvm->dirty_logging_enable_count == 0 &&
> +	    kvm->arch.pml_enabled) {
> +		kvm->arch.pml_enabled = false;
> +		kvm_make_all_cpus_request(kvm,
> +			KVM_REQ_UPDATE_VCPU_DIRTY_LOGGING_STATE);
> +	}
> +
>  	kvm_mmu_slot_set_dirty(kvm, slot);
>  }

...

> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ee4ac2618ec59..c6e5b026bbfe8 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -307,6 +307,7 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
>  {
>  	return kvm_make_all_cpus_request_except(kvm, req, NULL);
>  }
> +EXPORT_SYMBOL_GPL(kvm_make_all_cpus_request);

If we move enable_pml into x86.c then this export and several of the kvm_x86_ops
go away.  I know this because I have a series I was about to send that does that,
among several other things.  I suspect that kvm->arch.pml_enabled could also go
away, but that's just a guess.

Anyways, I'll work with you off-list to figure out a plan.  The easiest thing is
probably for me to tack it on to the end of my series.  I completely spaced on
the fact that my series would conflict with this code, sorry :-/