linux-kernel - Re: [PATCH v3 00/21] KVM: Dirty ring interface

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: <20200109171909-mutt-send-email-mst@kernel.org>
Date:   Thu, 9 Jan 2020 17:21:01 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Peter Xu <peterx@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Christophe de Dinechin <dinechin@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yan Zhao <yan.y.zhao@...el.com>,
        Jason Wang <jasowang@...hat.com>,
        Kevin Kevin <kevin.tian@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>
Subject: Re: [PATCH v3 00/21] KVM: Dirty ring interface

On Thu, Jan 09, 2020 at 09:51:50PM +0100, Paolo Bonzini wrote:
> On 09/01/20 20:13, Michael S. Tsirkin wrote:
> > That's one of the reasons I called for using something
> > resembling vring_packed_desc.
> 
> In principle it could make sense to use the ring-wrap detection
> mechanism from vring_packed_desc instead of the producer/consumer
> indices.  However, the element address/length indirection is unnecessary.
> 
> Also, unlike virtio, KVM needs to know if there are N free entries (N is
> ~512) before running a guest.  I'm not sure if that is possible with
> ring-wrap counters, while it's trivial with producer/consumer indices.
> 
> Paolo

Yes it's easy: just check whether current entry + 500 has been consumed.
Unless scatter/father is used, but then the answer is simple - just
don't use it :)

-- 
MST