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

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Date:   Thu, 11 Feb 2021 07:53:19 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Makarand Sonare <makarandsonare@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, 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 Thu, Feb 11, 2021, Paolo Bonzini wrote:
> On 10/02/21 22:23, Makarand Sonare wrote:
> > +void vmx_update_pml_in_vmcs(struct kvm_vcpu *vcpu)
> > +{
> > +	if (cpu_has_secondary_exec_ctrls()) {
> > +		if (is_guest_mode(vcpu)) {
> > +			to_vmx(vcpu)->nested.deferred_update_pml_vmcs = true;
> > +			return;
> > +		}
> > +
> > +		if (vcpu->kvm->arch.pml_enabled)
> > +			vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL,
> > +				SECONDARY_EXEC_ENABLE_PML);
> > +		else
> > +			vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL,
> > +				SECONDARY_EXEC_ENABLE_PML);
> > +	}
> > +}
> 
> 
> Since the execution controls are shadowed, they can be read quite
> efficiently.  This means that there's no need for
> vcpu->kvm->arch.pml_enabled, and also that the copy can be done
> unconditionally in prepare_vmcs02 and nested_vmx_vmexit.
> 
> If the above is not true, we should at least combine
> change_vmcs01_virtual_apic_mode, reload_vmcs01_apic_access_page and the new
> field in a single bit field, for example vmx->nested.dirty_vmcs01_fields or
> vmx->nested.vmexit_requests.
> 
> In any case I expect Sean to take care of submitting this patch and I have
> to do nothing more about it, right?

Right, we'll sort it out.