From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) (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 4EFCD423EA2; Wed, 19 Aug 2026 09:01:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787130106; cv=none; b=i94sEWU8+HnPbBUDExOtBhO5uQYbJp8G+iMUXCIY/+OT92gryWe+ionaVc6q2mPYHG5gNO0OiMhfVdCQN8kbMhywoT9WuEcdjyFE/G2FZNMFZg30U+MbBUc+nt0LxH2WDlEtDhxmATALryD74sYYovoRW4XyTDNTal5HI7Eb+u8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787130106; c=relaxed/simple; bh=98dOTjBq3wFdgdqGwfTTN7JMPJ0QM80kncC/dhsAaEM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KjWHLbul53wRzblYb6lte2yzrnKuad/JQ2pNP0Nkp4Yqc9Wb9yCDawJGoDyPY7v85KR8Q6wTyLWUlTN5X4/kDgE45NR6pCaGXK784vJu6pZh5oO1S6aJQkqEnXzYukq7PnpaGhbVsUQKJd1khuYIKbmby9dI/k4vbMe2P0HJlcc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=hSXRDztE; arc=none smtp.client-ip=198.175.65.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="hSXRDztE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1787130102; x=1818666102; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=98dOTjBq3wFdgdqGwfTTN7JMPJ0QM80kncC/dhsAaEM=; b=hSXRDztEuzK+vfxlEy/1ccqN6GCuPuovXdXysoD1h1iPqYv7jrVOCKa5 OsZWYAP4Wj89yslv9bXROmkbfotQ5gOSmkOCO6e23jlZjgp264DAWCvKz NgK+4Mtq/Bdx+2UMUyBvWYzgYC5Hb8I8idzrWtnjzNMY3q6KPrLFGW4uM I1+AvxdZtXkQVazYVmxBOshPIMl4aseUvBgWZPGpNQzPZO9xhjdzn2Iae xB3AV3idyX4Mp7qzpJ3Y6WijEWhJqbdl2hB6ytNluVkdm6LfctGnXLU0o Nsq/rTn5DUNPgy60hm22rEcKpwJUNNiHbSbId53nEACkYy5ThGaTZWQGr w==; X-CSE-ConnectionGUID: l4ZPcnSRRAy2LfEdhY2SmQ== X-CSE-MsgGUID: r418o4NdSISl02Jar7NfXA== X-IronPort-AV: E=McAfee;i="6800,10657,11879"; a="87656950" X-IronPort-AV: E=Sophos;i="6.25,231,1779174000"; d="scan'208";a="87656950" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Aug 2026 02:01:40 -0700 X-CSE-ConnectionGUID: 9ez7glO+TTyq5jZ/07zDlg== X-CSE-MsgGUID: Msh0ANjXTbieZObaUkO15Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,231,1779174000"; d="scan'208";a="270702846" Received: from unknown (HELO [10.238.2.33]) ([10.238.2.33]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Aug 2026 02:01:33 -0700 Message-ID: <481a39fa-d99f-4139-823b-1d9327c3a9c8@linux.intel.com> Date: Wed, 19 Aug 2026 17:01:30 +0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/7] KVM: x86: Virtualize LASS and advertise support to userspace To: Sohil Mehta Cc: kvm@vger.kernel.org, x86@kernel.org, Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Shuah Khan , Peter Zijlstra , "Chang S . Bae" , Kai Huang , Fuad Tabba , Chao Gao , Yosry Ahmed , Claudio Imbrenda , David Matlack , Bala-Vignesh-Reddy , Kishen Maloor , Rick Edgecombe , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260806011536.4172258-1-sohil.mehta@intel.com> <20260806011536.4172258-6-sohil.mehta@intel.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260806011536.4172258-6-sohil.mehta@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/6/2026 9:15 AM, Sohil Mehta wrote: > From: Zeng Guang > > Virtualize Linear Address Space Separation (LASS) by letting the guest > enable CR4.LASS[bit 27]. Allow the guest to set CR4.LASS only if LASS is > enumerated in the guest's CPUID. Set CR4.LASS in the emulated > IA32_VMX_CR4_FIXED1 MSR so that LASS can be enabled in nested VMX > operation as well. > > Keep CR4.LASS KVM-owned instead of making it guest-owned. LASS is > expected to be enabled once per vCPU at boot and rarely toggled at > runtime. > > LASS is enumerated by CPUID.(EAX=07H,ECX=1):EAX.LASS[bit 6] and only > works in IA-32e mode. Advertise LASS to userspace on 64-bit kernels and > only when it is supported by the host. Notably, it will not be exposed > to userspace if the deprecated vsyscall=emulate mode is set on the ^ Nit: mode could be dropped. > kernel command line. > > Signed-off-by: Zeng Guang > Signed-off-by: Binbin Wu > Signed-off-by: Sohil Mehta Reviewed-by: Binbin Wu