linux-kernel - Re: [PATCH 19/61] KVM: VMX: Add helpers to query Intel PT mode

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <33a4d99d-98da-0bd8-0f9c-fc04bef54350@redhat.com>
Date:   Tue, 25 Feb 2020 15:54:21 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 19/61] KVM: VMX: Add helpers to query Intel PT mode

On 24/02/20 23:18, Sean Christopherson wrote:
>>>  {
>>>  	u32 vmexit_ctrl = vmcs_config.vmexit_ctrl;
>>> -	if (pt_mode == PT_MODE_SYSTEM)
>>> +	if (vmx_pt_mode_is_system())
>> ... and here? I.e. to cover the currently unsupported 'host-only' mode.
> Hmm, good question.  I don't think so?  On VM-Enter, RTIT_CTL would need to
> be loaded to disable PT.  Clearing RTIT_CTL on VM-Exit would be redundant
> at that point[1].  And AIUI, the PIP for VM-Enter/VM-Exit isn't needed
> because there is no context switch from the decoder's perspective.

How does host-only mode differ from "host-guest but don't expose PT to
the guest"?  So I would say that host-only mode is a special case of
host-guest, not of system mode.

Paolo