linux-kernel - Re: [PATCH v4 02/19] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs

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Message-ID: <299817fc-0940-432c-bfbb-a02781a48c9f@zytor.com>
Date: Mon, 14 Apr 2025 09:53:45 -0700
From: Xin Li <xin@...or.com>
To: Chao Gao <chao.gao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        andrew.cooper3@...rix.com, luto@...nel.org, peterz@...radead.org,
        xin3.li@...el.com
Subject: Re: [PATCH v4 02/19] KVM: VMX: Initialize VM entry/exit FRED controls
 in vmcs_config

On 4/14/2025 12:41 AM, Chao Gao wrote:
>> +		{ VM_ENTRY_LOAD_IA32_FRED,		VM_EXIT_ACTIVATE_SECONDARY_CONTROLS },
> This line should be removed. It enforces that "Activate secondary controls"
> is supported iff FRED is supported, which isn't true.
> 
> Bit 3 of 2nd VM-exit controls is "Prematurely busy shadow stack". Some CPUs
> support it, but not FRED.

Sigh, 2nd time on the same shit.