linux-kernel - Re: [PATCH v2 6/6] KVM: nVMX: optimize prepare_vmcs02{,

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Message-ID: <2ed3d00b-bc99-2e2d-3a23-a86de767bfec@redhat.com>
Date:   Wed, 25 Jul 2018 15:31:47 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v2 6/6] KVM: nVMX: optimize prepare_vmcs02{,_full} for
 Enlightened VMCS case

On 25/07/2018 15:26, Vitaly Kuznetsov wrote:
> Doing it in nested_vmx_handle_enlightened_vmptrld() is even better: we
> can simplify copy_enlightened_to_vmcs12() too!

Yes, that's true!

> The other place where we set dirty_vmcs12 is the newly introduced
> vmx_set_nested_state() but I think I'm going to add support for eVMCS
> there later and just return something like -ENOTSUPP for now. Too many
> people work on nested simultaneously :-)

Hmm, I think that means you have to put the clean fields in the
vmx_nested struct.  Then it's really easy in vmx_set_nested_state to
clear all the clean bits.  Touching memory in vmx_set_nested_state is...
*puts on sunglasses* a touchy subject (see comment in kvm/queue's
enter_vmx_non_root_mode).

Thanks,

Paolo