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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <a18d5eb9-e796-1d09-b3d5-1573ad7b1d20@redhat.com>
Date:   Wed, 25 Jul 2018 16:39:11 +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 16:13, Vitaly Kuznetsov wrote:
> Paolo Bonzini <pbonzini@...hat.com> writes:
> 
>> On 25/07/2018 15:26, Vitaly Kuznetsov wrote:
>>
>>> 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).
>>
> 
> Not only clean fields, in case we can't touch memory in
> vmx_set_nested_state I guess we'll need to cache the whole eVMCS, just
> like we save cached_shadow_vmcs12. Anyway, let's eat the elephant one
> bite at a time :-)

You're right, but do we actually need to save the vmcs12 if eVMCS is
active?  The format would be different, but the size wouldn't.

Paolo