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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 83765C4345F for ; Thu, 2 May 2024 10:50:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=gJDmKgSmzLSOGKfpOczvG8SVVZEf0gqchUMTKnEwMn0=; b=UxYcum2QOCl3ze luaaqd65nYhLBp9EXzSagIV0bQt2OKXOVSMUWPdN+KYq56z4beYqRssm/pTf1ZwYheYCYUXKOcoft VkcBdsmIkZHBioXH4/FtNf+Z3R/K+Zi7HlHIC1VWjWz+ghtG1rHewHuiK3UQ5TAGLVXjVSlcNMYid MW1gBauy4+oeaqK3eHXPJ3LuHwXsHskQwRgLpSaq+vRdBGBFDQaNgSWK+AvORx4B5igOrhv61Sjks WtHhSrthLhajyiNzFzwoHW4XGrjTVt8FQ9S+FRuLWOo66PuK9Csk1Npx+FYsZ1lm/JPojNvvAX4uc hP+xtX+7VLiaWefUUqGg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s2U1F-0000000CPkY-3qh7; Thu, 02 May 2024 10:50:29 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:32c8:5054:ff:fe00:142]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s2U1C-0000000CPk0-1rrQ for linux-arm-kernel@lists.infradead.org; Thu, 02 May 2024 10:50:27 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=z6rERo+AyDCjavqLTFckp1YpHTpXK30bl2flTzGgKh4=; b=pYjBeGS+MErfdrH8W54b0VWDuS euZFo5BSf9VgccTYxIYh5goUeiSoaU/Jypg/VkzlNSzehUwYoyv0vG7v5SnYVYDN3nnrAbvJXToZh 8gjFMQls6RAGq0nL3fLDjOenVUIFse3BmA18xw11obJumJ0x+LSeymZvS/VfM6wJlYUTPuCeFn+h5 1u0caWVzhl0ss/OsNb5Lmmgxrt2VpKwPL4hEwHXB8/luJxzHUOTumcqZNFeNoztmjQJQ+PJCMEnPD iOI3lB6PH8sToZfRJ1fbaxEi11/Gbsu+kU8/87HKEZdG97S5Ps9oLonSPfqdAmhOhnSusrwqRzfxP hevoYwpQ==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:36402) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1s2U0y-0007B3-0g; Thu, 02 May 2024 11:50:12 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1s2U0x-0003az-0v; Thu, 02 May 2024 11:50:11 +0100 Date: Thu, 2 May 2024 11:50:10 +0100 From: "Russell King (Oracle)" To: Oliver Upton Cc: Marc Zyngier , Catalin Marinas , Will Deacon , James Morse , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [PATCH RFC] KVM: arm64: allow ID_MMFR4_EL1 to be writable Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240502_035026_525917_D322F111 X-CRM114-Status: GOOD ( 29.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 01, 2024 at 08:51:15PM +0100, Russell King (Oracle) wrote: > On Wed, May 01, 2024 at 06:59:17PM +0000, Oliver Upton wrote: > > On Wed, May 01, 2024 at 07:08:05PM +0100, Russell King (Oracle) wrote: > > > On Wed, May 01, 2024 at 05:57:20PM +0000, Oliver Upton wrote: > > > > Hi Russell, > > > > > > > > On Wed, May 01, 2024 at 06:06:51PM +0100, Russell King (Oracle) wrote: > > > > > Between 5.4 and 5.15, the guests view of HPDS, CnP, XNX and AC2 > > > > > changed their value on the same Neoverse N1 r3p1 hardware which makes > > > > > migrating between these kernels on the host problematical. > > > > > > > > It'd be helpful to expand a bit more on how these fields changed, better > > > > yet if we can blame it back to a commit. I'm guessing the only direction > > > > of migration you care about is old -> new then? > > > > > > Yes. For MMFR4_EL1, we see 0 with our 5.4 based kernel, and 0x21110 > > > with our 5.15 kernel. I've been looking at tracking down which commit > > > is responsible but I've come up with nothing that fits. > > > > > > The only change I can see is the FTR definition for MMFR4, but this > > > always included 4:7 (AC2) which changed 0 -> 1. So... no idea what > > > commit caused the change. > > > > > > There are a load of other registers that we need sorting, but this > > > is just a test forray into attempting to solve this. > > > > Got it, let me see if I can find it then. Do share that list of > > problematic registers when you have it, hopefully this isn't the tip of > > the iceberg... > > There unfortunately is an iceberg, but hopefully it isn't big enough to > sink a ship! > > Besides ID_MMFR4_EL1, here are the other differences we've identified. > Note that these are Oracle's UEK kernels, so based on stable kernel > branches. > > Register Field 5.4.x 5.15.x > ID_PFR0_EL1 CSV2 0 1 > ID_ISAR6_EL1 DP 0 1 > ID_PFR2_EL1 SSBS 0 1 > CSV3 0 1 > ID_AA64DFR0_EL1 PMSVer 1 0 > DebugVer 8 6 > ID_AA64MMFR1_EL1 XNX 0 1 > ID_AA64MMFR2_EL1 EVT 0 1 > KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2 > 0x12 0 I'm finding sys_regs.c very unintuitive for working out what we allow to be written, because it's all coded in negative-logic. By that I mean the mask values are all ~(what-we-don't-allow) rather than a positive this-is-what-we-allow. So I've ended up creating a table, looking up the registers and working out what's read-only and what's read-write. >From that, I can see (for example) that from the ISAR6_EL1 register, the field names appear in the AA64ISAR0_EL1 and AA64ISAR1_EL1 registers, and all non-res0 fields are writable. It is therefore my intention to submit a patch doing this: - AA32_ID_SANITISED(ID_ISAR6_EL1), + AA32_ID_WRITABLE(ID_ISAR6_EL1, ID_ISAR6_EL1_I8MM | + ID_ISAR6_EL1_BF16 | + ID_ISAR6_EL1_SPECRES | + ID_ISAR6_EL1_SB | + ID_ISAR6_EL1_FHM | + ID_ISAR6_EL1_DP | + ID_ISAR6_EL1_JSCVT), which, like the MMFR4 patch, uses positive logic for what we allow to be changed, even though this is equivalent to ~ID_ISAR6_EL1_RES0 which tells us nothing without either looking up in the spec, or looking at the generated sysreg-defs.h to figure it out. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel