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

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Message-ID: <a95b2a12-f3a9-b930-49fe-46c2278df34d@redhat.com>
Date:   Fri, 18 May 2018 11:41:23 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Eduardo Habkost <ehabkost@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Cc:     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 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