linux-kernel - Re: [PATCH 1/2] x86/hyperv: Allow guests to enable InvariantTSC

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Message-ID: <20191003160326.GA22098@andrea.guest.corp.microsoft.com>
Date:   Thu, 3 Oct 2019 18:03:26 +0200
From:   Andrea Parri <parri.andrea@...il.com>
To:     linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        x86@...nel.org
Cc:     "K . Y . Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: Re: [PATCH 1/2] x86/hyperv: Allow guests to enable InvariantTSC


On Thu, Oct 03, 2019 at 05:52:00PM +0200, Andrea Parri wrote:
> If the hardware supports TSC scaling, Hyper-V will set bit 15 of the
> HV_PARTITION_PRIVILEGE_MASK in guest VMs with a compatible Hyper-V
> configuration version.  Bit 15 corresponds to the
> AccessTscInvariantControls privilege.  If this privilege bit is set,
> guests can access the HvSyntheticInvariantTscControl MSR: guests can
> set bit 0 of this synthetic MSR to enable the InvariantTSC feature.
> After setting the synthetic MSR, CPUID will enumerate support for
> InvariantTSC.
> 
> Signed-off-by: Andrea Parri <parri.andrea@...il.com>

Subject should have been "[PATCH] ...", i.e., there is no 2/2 planned
(not for this patchset at least).  Please let me know if I should re-
submit with the subject fixed.

Thanks,
  Andrea