From nobody Sun Dec 14 23:36:31 2025 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 568102F7AB1; Sun, 26 Oct 2025 20:20:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761510033; cv=none; b=k9qkLsEITHdFONj8LgLY2Ts9nOcNVNVy4buqVAiw0RWr6uV6tMLghIHAMPC3lqHTQm0i48qj7mJryFJss92kLtSHxvmy/VzgHb1KqG7tkk8MLEbOhPgVTZ8O6g4E2MburzrpgGF08NVqu+IQx0WgGlvfriuKbiz3yRUrZyWbdiI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761510033; c=relaxed/simple; bh=9VokAk414snLBXF3pyB7JHAuMHOkiiRHlOL/Ix4S4e0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CDbV25k7YisSz3j34+Iz4fN8KXuLjKp+nduYCyWyP4ZI7SX5vtlvLeHXyOxvvrDICRRJqG2KJKNcroHqyaP5dQOpkW4+NSKvdt375RZVKo+9bnuaeSsVbWiA80uGX8YwsJBJCVJPWB5isC1YinwNR32wKujUsunsYLS5I5/wpzo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=eRId25kd; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="eRId25kd" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 59QKJBkS505258 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sun, 26 Oct 2025 13:19:29 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 59QKJBkS505258 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025102301; t=1761509970; bh=8UDLl5WkXPSsKyh6NlsnUJ4bx5FWuZND7Ll3P/1c8gM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eRId25kdLnDWL+6fkOVYDtCjNl8lyo3QpaH4m2Ce940hAtXPcMUBtZi5nM508X/wY SfjW//8NCJTYwYf5rFa/McYi9KVa/iDZrFA3v3W+tlWORuydptuYUcxgsJwqmM2qVG sy6DXoX7yijkpjsbRE8HtMoT72EhSi4tB0K9a4ZZIKFuu3akqBlED0yKhQL7pEI82/ wMdakm/otgy+afqNmRx1vSz1EREIDY6GX14QEjRuXjl/lP/EVQ3TMspNye6qV3YmUX 4dcteTPGz2excBC01EtQlIjuuJgssAzCAX3CvikR0TCatMpif83Xb8NX8N+IoKo/bX A3bHoV24/CmEA== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org Cc: pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, xin@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org, sohil.mehta@intel.com Subject: [PATCH v9 11/22] KVM: x86: Add a helper to detect if FRED is enabled for a vCPU Date: Sun, 26 Oct 2025 13:18:59 -0700 Message-ID: <20251026201911.505204-12-xin@zytor.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251026201911.505204-1-xin@zytor.com> References: <20251026201911.505204-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Xin Li Signed-off-by: Xin Li [ Sean: removed the "kvm_" prefix from the function name ] Signed-off-by: Sean Christopherson Signed-off-by: Xin Li (Intel) Tested-by: Shan Kang Tested-by: Xuelian Guo Reviewed-by: Chao Gao --- Change in v5: * Add TB from Xuelian Guo. --- arch/x86/kvm/kvm_cache_regs.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h index 8ddb01191d6f..3c8dbb77d7d4 100644 --- a/arch/x86/kvm/kvm_cache_regs.h +++ b/arch/x86/kvm/kvm_cache_regs.h @@ -205,6 +205,21 @@ static __always_inline bool kvm_is_cr4_bit_set(struct = kvm_vcpu *vcpu, return !!kvm_read_cr4_bits(vcpu, cr4_bit); } =20 +/* + * It's enough to check just CR4.FRED (X86_CR4_FRED) to tell if + * a vCPU is running with FRED enabled, because: + * 1) CR4.FRED can be set to 1 only _after_ IA32_EFER.LMA =3D 1. + * 2) To leave IA-32e mode, CR4.FRED must be cleared first. + */ +static inline bool is_fred_enabled(struct kvm_vcpu *vcpu) +{ +#ifdef CONFIG_X86_64 + return kvm_is_cr4_bit_set(vcpu, X86_CR4_FRED); +#else + return false; +#endif +} + static inline ulong kvm_read_cr3(struct kvm_vcpu *vcpu) { if (!kvm_register_is_available(vcpu, VCPU_EXREG_CR3)) --=20 2.51.0