linux-kernel - Re: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to x86

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Message-ID: <1b97ea8f-84fe-ac3c-7492-4d1675f7f074@intel.com>
Date:   Tue, 1 Aug 2023 14:52:25 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Saurabh Sengar <ssengar@...ux.microsoft.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Cc:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "hpa@...or.com" <hpa@...or.com>
Subject: Re: [EXTERNAL] Re: [PATCH v3] x86/hyperv: add noop functions to
 x86_init mpparse functions

On 7/21/23 05:58, Saurabh Singh Sengar wrote:
>> On Fri, Jun 23, 2023 at 09:28:08AM -0700, Saurabh Sengar wrote:
>>> Hyper-V can run VMs at different privilege "levels" known as Virtual
>>> Trust Levels (VTL). Sometimes, it chooses to run two different VMs at
>>> different levels but they share some of their address space. In such
>>> setups VTL2 (higher level VM) has visibility of all of the
>>> VTL0 (level 0) memory space.
>>>
>>> When the CONFIG_X86_MPPARSE is enabled for VTL2, the VTL2 kernel
>>> performs a search within the low memory to locate MP tables. However,
>>> in systems where VTL0 manages the low memory and may contain valid
>>> tables, this scanning can result in incorrect MP table information
>>> being provided to the VTL2 kernel, mistakenly considering VTL0's MP
>>> table as its own
>>>
>>> Add noop functions to avoid MP parse scan by VTL2.
>>>
>>> Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
>> Hi Dave, are you happy with the commit message?
> HI Dave,
> 
> If there is no concern, can I get your ack

Looks sane:

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>

Although, if you muck with this any more having actual facts on what the
"incorrect MP table information" causes would be nice too.