From nobody Wed Dec 24 22:09:26 2025 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.20]) (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 E89EC171AA; Wed, 24 Jan 2024 07:42:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=134.134.136.20 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706082141; cv=none; b=XBgQpSfZbOEunaI82rU2C0v8DfVTJ/EPRmCPG5nN0WVShpl1ePg/kCpVRyY8JJeW6oRSx2l5RxhgCqFPZ872Bubz0zzA64aBO8L5JeUWYKOXq7r3p+dwVREBbjV/xywDH4+gEPpyVluVscY9MMvBpc0ROO5i72gGMugXHiwZ8s8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706082141; c=relaxed/simple; bh=rpFgire7Svqru/HfpQ1b16RkVx0842HOL7xbgXY2vaQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=f0UcyazsjAEUmn8g2uHDmiUNyZtwYLIAqf5BPJGhMr2C7kfbFttpJjfB4MTchyazvUb+a0AYa/KsyucQMMwZfTEna6nOdo/u+hPdjvQTt3Od1+PUl/3tgLaYnS9vyd8ROA4HQNdCU3fjMBR/chysWEX3c2arsCfQsF4/rWEYJQI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=DxEim5OK; arc=none smtp.client-ip=134.134.136.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none 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="DxEim5OK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1706082139; x=1737618139; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=rpFgire7Svqru/HfpQ1b16RkVx0842HOL7xbgXY2vaQ=; b=DxEim5OKkxWhq/fmmpcb6qriPpEEMdNxTU/AWUYZDgVotvNyZ2MeOM0A tnTekbp8xiaqRMIrXmjE/GhfNom8ybwX+oBMmcFzPNPEsDnf1Bx3jk5N6 PWK0YOeKHHCkGiY1MkFlbuW0vgyTG94IqTTtiey4JRd9jQq3yvgA8tU1C x+BgE1dl5WQzfkcqg6VerSEeQ1RvY6ay6cF7d8vtMBz5YLogLA8jqWmTL Y8OulnN07dkGnSQWH8Z+2vcPd3potfsaaBj9qOs8yNiYYD2wYTNf6xNyx /BP1SFyRD1rxKnY82lehskJC2l5qxN/LQq4ReJZGpgMVnyjFGBrfxsmgm w==; X-IronPort-AV: E=McAfee;i="6600,9927,10962"; a="392184641" X-IronPort-AV: E=Sophos;i="6.05,216,1701158400"; d="scan'208";a="392184641" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2024 23:42:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,216,1701158400"; d="scan'208";a="1819150" Received: from bbaidya-mobl.amr.corp.intel.com (HELO desk) ([10.209.53.134]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2024 23:42:12 -0800 Date: Tue, 23 Jan 2024 23:42:11 -0800 From: Pawan Gupta To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Josh Poimboeuf , Andy Lutomirski , Jonathan Corbet , Sean Christopherson , Paolo Bonzini , tony.luck@intel.com, ak@linux.intel.com, tim.c.chen@linux.intel.com, Andrew Cooper , Nikolay Borisov Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, Alyssa Milburn , Daniel Sneddon , antonio.gomez.iglesias@linux.intel.com, Pawan Gupta Subject: [PATCH v6 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Message-ID: <20240123-delay-verw-v6-5-a8206baca7d3@linux.intel.com> X-Mailer: b4 0.12.3 References: <20240123-delay-verw-v6-0-a8206baca7d3@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240123-delay-verw-v6-0-a8206baca7d3@linux.intel.com> Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Sean Christopherson Use EFLAGS.CF instead of EFLAGS.ZF to track whether to use VMRESUME versus VMLAUNCH. Freeing up EFLAGS.ZF will allow doing VERW, which clobbers ZF, for MDS mitigations as late as possible without needing to duplicate VERW for both paths. Reviewed-by: Nikolay Borisov Signed-off-by: Sean Christopherson Signed-off-by: Pawan Gupta --- arch/x86/kvm/vmx/run_flags.h | 7 +++++-- arch/x86/kvm/vmx/vmenter.S | 6 +++--- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx/run_flags.h b/arch/x86/kvm/vmx/run_flags.h index edc3f16cc189..6a9bfdfbb6e5 100644 --- a/arch/x86/kvm/vmx/run_flags.h +++ b/arch/x86/kvm/vmx/run_flags.h @@ -2,7 +2,10 @@ #ifndef __KVM_X86_VMX_RUN_FLAGS_H #define __KVM_X86_VMX_RUN_FLAGS_H =20 -#define VMX_RUN_VMRESUME (1 << 0) -#define VMX_RUN_SAVE_SPEC_CTRL (1 << 1) +#define VMX_RUN_VMRESUME_SHIFT 0 +#define VMX_RUN_SAVE_SPEC_CTRL_SHIFT 1 + +#define VMX_RUN_VMRESUME BIT(VMX_RUN_VMRESUME_SHIFT) +#define VMX_RUN_SAVE_SPEC_CTRL BIT(VMX_RUN_SAVE_SPEC_CTRL_SHIFT) =20 #endif /* __KVM_X86_VMX_RUN_FLAGS_H */ diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index be275a0410a8..b3b13ec04bac 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -139,7 +139,7 @@ SYM_FUNC_START(__vmx_vcpu_run) mov (%_ASM_SP), %_ASM_AX =20 /* Check if vmlaunch or vmresume is needed */ - test $VMX_RUN_VMRESUME, %ebx + bt $VMX_RUN_VMRESUME_SHIFT, %ebx =20 /* Load guest registers. Don't clobber flags. */ mov VCPU_RCX(%_ASM_AX), %_ASM_CX @@ -161,8 +161,8 @@ SYM_FUNC_START(__vmx_vcpu_run) /* Load guest RAX. This kills the @regs pointer! */ mov VCPU_RAX(%_ASM_AX), %_ASM_AX =20 - /* Check EFLAGS.ZF from 'test VMX_RUN_VMRESUME' above */ - jz .Lvmlaunch + /* Check EFLAGS.CF from the VMX_RUN_VMRESUME bit test above. */ + jnc .Lvmlaunch =20 /* * After a successful VMRESUME/VMLAUNCH, control flow "magically" --=20 2.34.1