From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4165EC47254 for ; Tue, 5 May 2020 10:42:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1BBE520735 for ; Tue, 5 May 2020 10:42:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588675378; bh=NLCbmdO5jXwPTRJmev5nd5sqfYdfydo3KQgdzeupCVw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=NfjSd6jd7Jby0c15HqNFz6CoH+TfZWRirT8bSTHKdkLwaF9yenG7jw6sqPyHoDKRt MUkNgPrMMmAHatmv5Xo7Gb33lVKYFr7XY7z4w0ehv3mPQfV/d4sUzxLOdDiJZfqibG r3JWmrq4R5qmZ4F2I/vP0v43lmBoRJnOtO2VaaYs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728711AbgEEKm5 (ORCPT ); Tue, 5 May 2020 06:42:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:54904 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728660AbgEEKm5 (ORCPT ); Tue, 5 May 2020 06:42:57 -0400 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C1FFD206A5; Tue, 5 May 2020 10:42:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588675376; bh=NLCbmdO5jXwPTRJmev5nd5sqfYdfydo3KQgdzeupCVw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2Jo+b3eyoAVOg/5340CGqyTb2jUUFWj37ojZOsHWNQHkvvtQZjiUq62H2OVcZpHI8 LNS3z8WXpoQpIIY5GRyImbq8O3W8Ogr1KK3IQrKm19FzqGdfXNkkrLP5pfBeMviVoF Fud8qYMJPVqmMU28sgyb2quRfLYtIq3//48fkSKA= Date: Tue, 5 May 2020 11:42:51 +0100 From: Will Deacon To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Marc Zyngier , Mark Rutland , James Morse , Suzuki K Poulose , linux-kernel@vger.kernel.org Subject: Re: [PATCH V3 02/16] arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register Message-ID: <20200505104250.GA19710@willie-the-truck> References: <1588426445-24344-1-git-send-email-anshuman.khandual@arm.com> <1588426445-24344-3-git-send-email-anshuman.khandual@arm.com> <20200504202453.GA5012@willie-the-truck> <56cd3062-a0c2-6cdf-b7c6-c2b7bf56d23b@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56cd3062-a0c2-6cdf-b7c6-c2b7bf56d23b@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 05, 2020 at 12:20:41PM +0530, Anshuman Khandual wrote: > On 05/05/2020 01:54 AM, Will Deacon wrote: > > On Sat, May 02, 2020 at 07:03:51PM +0530, Anshuman Khandual wrote: > >> ID_DFR0 based TraceFilt feature should not be exposed to guests. Hence lets > >> drop it. > >> > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Cc: Marc Zyngier > >> Cc: Mark Rutland > >> Cc: James Morse > >> Cc: Suzuki K Poulose > >> Cc: linux-arm-kernel@lists.infradead.org > >> Cc: linux-kernel@vger.kernel.org > >> > >> Suggested-by: Mark Rutland > >> Reviewed-by: Suzuki K Poulose > >> Signed-off-by: Anshuman Khandual > >> --- > >> arch/arm64/kernel/cpufeature.c | 1 - > >> 1 file changed, 1 deletion(-) > >> > >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > >> index 6d032fbe416f..51386dade423 100644 > >> --- a/arch/arm64/kernel/cpufeature.c > >> +++ b/arch/arm64/kernel/cpufeature.c > >> @@ -435,7 +435,6 @@ static const struct arm64_ftr_bits ftr_id_pfr1[] = { > >> }; > >> > >> static const struct arm64_ftr_bits ftr_id_dfr0[] = { > >> - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0), > > > > Hmm, this still confuses me. Is this not now FTR_NONSTRICT? Why is that ok? > > Mark had mentioned about it earlier (https://patchwork.kernel.org/patch/11287805/) > Did I misinterpret the first part ? Could not figure "capping the emulated debug > features" part. Probably, Mark could give some more details. > > From the earlier discussion: > > * ID_DFR0 fields need more thought; we should limit what we expose here. > I don't think it's valid for us to expose TraceFilt, and I suspect we > need to add capping for debug features we currently emulate. Sorry, I for confused (again) by the cpufeature code :) I'm going to add the following to my comment: diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c1d44d127baa..9b05843d67af 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -53,6 +53,11 @@ * arbitrary physical CPUs, but some features not present on the host are * also advertised and emulated. Look at sys_reg_descs[] for the gory * details. + * + * - If the arm64_ftr_bits[] for a register has a missing field, then this + * field is treated as STRICT RES0, including for read_sanitised_ftr_reg(). + * This is stronger than FTR_HIDDEN and can be used to hide features from + * KVM guests. */ #define pr_fmt(fmt) "CPU features: " fmt However, I think we really want to get rid of ftr_generic_32bits[] entirely and spell out all of the register fields, even just using comments for the fields we're omitting: @@ -425,7 +430,7 @@ static const struct arm64_ftr_bits ftr_id_pfr1[] = { }; static const struct arm64_ftr_bits ftr_id_dfr0[] = { - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0), + /* 31:28 TraceFilt */ S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 24, 4, 0xf), /* PerfMon */ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 20, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 16, 4, 0), Longer term, I think we'll probably want to handle these within ARM64_FTR_BITS, as we may end up with features that we want to hide from KVM guests but not from the host kernel. Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5D24C47247 for ; Tue, 5 May 2020 10:43:00 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7E547206A5 for ; Tue, 5 May 2020 10:43:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Zi0H2v1O"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="2Jo+b3ey" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E547206A5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=CT/pmjgWB91FOkvTVspJfTsJhvqzB3lfJD2Ps+WTwMo=; b=Zi0H2v1OyIHwDx L97BMU2LMmuvU6i9dwiVfhDW0lHcpAMQgeCzp2VE7faW6giGFXASjlFqohGC/Qh7g0rRmTYcdodrl nRzG9NZTuuMC183D3TrO9vJf2I6CmNnx1a3UsYnq0lehfzEC5blaWzyaGig2+N72O7vEAKmWJhifp BcLgDApFawz4LjLEjQI5Jdd+TTitkcxxzmccJRcwoDgugeszCJh8NXZOYqs2oZjLCbxPpWppIqiPE hgWLPFnQpPTnXUfVYXhQA1fHuMtNo3msSnQ+eV4VPVNwi4wUKnuGwn9u4q4CthrwtCNdemJcUcI1P Hpv205/oMGVvPs2oCIQw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVv2R-0006yJ-F3; Tue, 05 May 2020 10:42:59 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVv2O-0006xh-La for linux-arm-kernel@lists.infradead.org; Tue, 05 May 2020 10:42:58 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C1FFD206A5; Tue, 5 May 2020 10:42:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588675376; bh=NLCbmdO5jXwPTRJmev5nd5sqfYdfydo3KQgdzeupCVw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2Jo+b3eyoAVOg/5340CGqyTb2jUUFWj37ojZOsHWNQHkvvtQZjiUq62H2OVcZpHI8 LNS3z8WXpoQpIIY5GRyImbq8O3W8Ogr1KK3IQrKm19FzqGdfXNkkrLP5pfBeMviVoF Fud8qYMJPVqmMU28sgyb2quRfLYtIq3//48fkSKA= Date: Tue, 5 May 2020 11:42:51 +0100 From: Will Deacon To: Anshuman Khandual Subject: Re: [PATCH V3 02/16] arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register Message-ID: <20200505104250.GA19710@willie-the-truck> References: <1588426445-24344-1-git-send-email-anshuman.khandual@arm.com> <1588426445-24344-3-git-send-email-anshuman.khandual@arm.com> <20200504202453.GA5012@willie-the-truck> <56cd3062-a0c2-6cdf-b7c6-c2b7bf56d23b@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <56cd3062-a0c2-6cdf-b7c6-c2b7bf56d23b@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200505_034256_748734_5B854A8F X-CRM114-Status: GOOD ( 22.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Suzuki K Poulose , Catalin Marinas , linux-kernel@vger.kernel.org, James Morse , Marc Zyngier , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 05, 2020 at 12:20:41PM +0530, Anshuman Khandual wrote: > On 05/05/2020 01:54 AM, Will Deacon wrote: > > On Sat, May 02, 2020 at 07:03:51PM +0530, Anshuman Khandual wrote: > >> ID_DFR0 based TraceFilt feature should not be exposed to guests. Hence lets > >> drop it. > >> > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Cc: Marc Zyngier > >> Cc: Mark Rutland > >> Cc: James Morse > >> Cc: Suzuki K Poulose > >> Cc: linux-arm-kernel@lists.infradead.org > >> Cc: linux-kernel@vger.kernel.org > >> > >> Suggested-by: Mark Rutland > >> Reviewed-by: Suzuki K Poulose > >> Signed-off-by: Anshuman Khandual > >> --- > >> arch/arm64/kernel/cpufeature.c | 1 - > >> 1 file changed, 1 deletion(-) > >> > >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > >> index 6d032fbe416f..51386dade423 100644 > >> --- a/arch/arm64/kernel/cpufeature.c > >> +++ b/arch/arm64/kernel/cpufeature.c > >> @@ -435,7 +435,6 @@ static const struct arm64_ftr_bits ftr_id_pfr1[] = { > >> }; > >> > >> static const struct arm64_ftr_bits ftr_id_dfr0[] = { > >> - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0), > > > > Hmm, this still confuses me. Is this not now FTR_NONSTRICT? Why is that ok? > > Mark had mentioned about it earlier (https://patchwork.kernel.org/patch/11287805/) > Did I misinterpret the first part ? Could not figure "capping the emulated debug > features" part. Probably, Mark could give some more details. > > From the earlier discussion: > > * ID_DFR0 fields need more thought; we should limit what we expose here. > I don't think it's valid for us to expose TraceFilt, and I suspect we > need to add capping for debug features we currently emulate. Sorry, I for confused (again) by the cpufeature code :) I'm going to add the following to my comment: diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c1d44d127baa..9b05843d67af 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -53,6 +53,11 @@ * arbitrary physical CPUs, but some features not present on the host are * also advertised and emulated. Look at sys_reg_descs[] for the gory * details. + * + * - If the arm64_ftr_bits[] for a register has a missing field, then this + * field is treated as STRICT RES0, including for read_sanitised_ftr_reg(). + * This is stronger than FTR_HIDDEN and can be used to hide features from + * KVM guests. */ #define pr_fmt(fmt) "CPU features: " fmt However, I think we really want to get rid of ftr_generic_32bits[] entirely and spell out all of the register fields, even just using comments for the fields we're omitting: @@ -425,7 +430,7 @@ static const struct arm64_ftr_bits ftr_id_pfr1[] = { }; static const struct arm64_ftr_bits ftr_id_dfr0[] = { - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0), + /* 31:28 TraceFilt */ S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 24, 4, 0xf), /* PerfMon */ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 20, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 16, 4, 0), Longer term, I think we'll probably want to handle these within ARM64_FTR_BITS, as we may end up with features that we want to hide from KVM guests but not from the host kernel. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel