linux-kernel - Re: [PATCH RFC hack dont apply] intel

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Message-ID: <CAJZ5v0hz+KDGVdz+X=98p51fOpk6AAa3CmL-asWw3uZg12X-Lw@mail.gmail.com>
Date:   Sat, 30 Sep 2017 01:21:43 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Yang Zhang <yang.zhang.wz@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kvm@...r.kernel.org, Wanpeng Li <wanpeng.li@...mail.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, rkrcmar@...hat.com,
        dmatlack@...gle.com, agraf@...e.de,
        Peter Zijlstra <peterz@...radead.org>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH RFC hack dont apply] intel_idle: support running within a VM

On Sat, Sep 30, 2017 at 12:01 AM, Michael S. Tsirkin <mst@...hat.com> wrote:
> intel idle driver does not DTRT when running within a VM:
> when going into a deep power state, the right thing to
> do is to exit to hypervisor rather than to keep polling
> within guest using mwait.
>
> Currently the solution is just to exit to hypervisor each time we go
> idle - this is why kvm does not expose the mwait leaf to guests even
> when it allows guests to do mwait.
>
> But that's not ideal - it seems better to use the idle driver to guess
> when will the next interrupt arrive.

The idle driver alone is not sufficient for that, though.

Thanks,
Rafael