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

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Message-ID: <ZMriW7IWemouYB43@liuwe-devbox-debian-v2>
Date:   Wed, 2 Aug 2023 23:10:19 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Saurabh Sengar <ssengar@...ux.microsoft.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        mikelley@...rosoft.com, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH v3] x86/hyperv: add noop functions to x86_init mpparse
 functions

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>

Applied to hyperv-fixes. Thanks.