linux-kernel - Re: [PATCH v9 02/22] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs

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Message-Id: <4FCC46DA-37E6-4C0A-ABDF-D1278502732C@zytor.com>
Date: Thu, 22 Jan 2026 09:57:44 -0800
From: Xin Li <xin@...or.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, peterz@...radead.org, andrew.cooper3@...rix.com,
        chao.gao@...el.com, hch@...radead.org, sohil.mehta@...el.com
Subject: Re: [PATCH v9 02/22] KVM: VMX: Initialize VM entry/exit FRED controls
 in vmcs_config



> On Jan 20, 2026, at 1:24 AM, Binbin Wu <binbin.wu@...ux.intel.com> wrote:
> 
>> 
>> Setup VM entry/exit FRED controls in the global vmcs_config for proper
>> FRED VMCS fields management:
>>  1) load guest FRED state upon VM entry.
>>  2) save guest FRED state during VM exit.
>>  3) load host FRED state during VM exit.
>> 
> 
> Nit:
> I think it's worth noting that IA32_FRED_RSP0 and IA32_FRED_SSP0 are treated
> differently. The change log might need more context on which MSRs are
> atomically switched in order to describe that though.

I deliberately omitted this point, as I felt that mentioning special cases
would be a distraction within a patch intended for the common framework.

In the overall patch series, this particular patch is like initially claiming
FRED simplifies virtualization state management, only to introduce complexities
in subsequent patches.