linux-kernel - Re: [PATCH] kvm: rename HINTS_DEDICATED to KVM_HINTS

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Date:   Fri, 18 May 2018 15:47:53 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Eduardo Habkost <ehabkost@...hat.com>,
        linux-kernel@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] kvm: rename HINTS_DEDICATED to KVM_HINTS_REALTIME

On Fri, May 18, 2018 at 11:41:23AM +0200, Paolo Bonzini wrote:
> On 17/05/2018 20:46, Eduardo Habkost wrote:
> > My understanding of the original patch is that the intention is
> > to tell the guest that it is very unlikely to be preempted, so it
> > can choose a more appropriate spinlock implementation.  This
> > description implies that the guest will never be preempted, which
> > is much stronger guarantee.
> > 
> > Isn't this new description incompatible with existing usage of
> > the hint, which might include people who just use vCPU pinning
> > but no mlock?
> 
> If you use hugetlbfs and vhost-user you don't really need mlock for the
> QEMU process, do you?  The QEMU process is not doing much in that case
> and hugetlbfs gives you pinned memory automatically.
> 
> Paolo

Same with PCI device passthrough: VFIO pins all guest memory right now.

-- 
MST