linux-kernel - Re: [PATCH] KVM: x86/svm: Add module param to control PMU virtualization

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]

Date:   Sat, 11 Dec 2021 03:15:25 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Like Xu <like.xu.linux@...il.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86/svm: Add module param to control PMU
 virtualization

On 12/10/21 20:25, Jim Mattson wrote:
> In the long run, I'd like to be able to override this system-wide
> setting on a per-VM basis, for VMs that I trust. (Of course, this
> implies that I trust the userspace process as well.)
> 
> How would you feel if we were to add a kvm ioctl to override this
> setting, for a particular VM, guarded by an appropriate permissions
> check, like capable(CAP_SYS_ADMIN) or capable(CAP_SYS_MODULE)?

What's the rationale for guarding this with a capability check?  IIRC 
you don't have such checks for perf_event_open (apart for getting kernel 
addresses, which is not a problem for virtualization).

Paolo