linux-kernel - Re: [PATCH v9 09/22] KVM: VMX: Save/restore guest FRED RSP0

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Message-ID: <aRQiOVfJg2PwyEdk@intel.com>
Date: Wed, 12 Nov 2025 13:59:21 +0800
From: Chao Gao <chao.gao@...el.com>
To: "Xin Li (Intel)" <xin@...or.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>,
	<hch@...radead.org>, <sohil.mehta@...el.com>
Subject: Re: [PATCH v9 09/22] KVM: VMX: Save/restore guest FRED RSP0

On Sun, Oct 26, 2025 at 01:18:57PM -0700, Xin Li (Intel) wrote:
>From: Xin Li <xin3.li@...el.com>
>
>Save guest FRED RSP0 in vmx_prepare_switch_to_host() and restore it
>in vmx_prepare_switch_to_guest() because MSR_IA32_FRED_RSP0 is passed
>through to the guest, thus is volatile/unknown.
>
>Note, host FRED RSP0 is restored in arch_exit_to_user_mode_prepare(),
>regardless of whether it is modified in KVM.
>
>Signed-off-by: Xin Li <xin3.li@...el.com>
>Signed-off-by: Xin Li (Intel) <xin@...or.com>
>Tested-by: Shan Kang <shan.kang@...el.com>
>Tested-by: Xuelian Guo <xuelian.guo@...el.com>

Reviewed-by: Chao Gao <chao.gao@...el.com>