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 5EA9EC27C4F for ; Fri, 21 Jun 2024 07:53:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=nXoBVk5kqzN1mCR3O5FxWCdVY0e1JqmsClbJIb/At4c=; b=a6Tc/ukKwQXxoFsnCl7tEeCPgN 5uOEUHD9dcyqNY0i5q2UCBkHOz0j4kiXtQ1ipd2/GVzGILUNZGEAZ9rs+ww0LzAtlJM6SwkgNXWA+ M1rSgK/Exc23Cd/XnFKa95zFVDdPujeHzSeKCfZ2B6H8XLigh8VfcGhJ2u+QdAOZp53VyBNvQ+Eiw ugHeQ17wPN2vSiPRMAboLFxqX/c7y+5B8zJ0n7dC2thh/4zmDy6V2uE/SaSFg7g5AeaKYtB4mhsmF ynR02/uZiLduGGrQYJl1VFS2FysI/9ZmNX9wGXpLtPsTrQud3DHLqNdriG/SSfachPTZX2ojOJ7jj 3VhbNTGA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sKZ5Y-00000008DNG-1EMp; Fri, 21 Jun 2024 07:53:40 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sKZ5U-00000008DMJ-2Op8 for linux-arm-kernel@lists.infradead.org; Fri, 21 Jun 2024 07:53:37 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id CA7ED6247A; Fri, 21 Jun 2024 07:53:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79671C2BBFC; Fri, 21 Jun 2024 07:53:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718956415; bh=eWeBwZ8/Lk6nImbfjWKt6XAuHYSDXDTd7xgQ3zt0uuA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=tVJlnJCGU3Ze6y91aA9mNXAeaKUrXYNa2sVodHGKsiRh4ebOIw1qfrUjg1SqtmC7V Bb6ECx/rwVvmajkN/+95vkWcjK5DDb0Qf03sBEEYO14PYePRkjb4FRV2BqQvIYA3Wc y+/jIbcCr0d7hU3OTrZYEoXzuEhQywVCHr0Ks0MlYSYje9ufuEM0J6LylY9RxgZPb2 a7dUPFSwffA4Yu6406bblU23YZcuYwkgS95qvQ88rZuGyziJ9V/ahHxPv2s2c9BNYO ETQwhiHXSXH+ClJG5vttCBYf4kOm3BvHBOHxN2y0GUk4VLaOeHjSRq3d9ZB97ymNC7 jmhYrDCmkg8Kw== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1sKZ5R-0062nT-7i; Fri, 21 Jun 2024 08:53:33 +0100 Date: Fri, 21 Jun 2024 08:53:32 +0100 Message-ID: <861q4qk9z7.wl-maz@kernel.org> From: Marc Zyngier To: Shaoqin Huang Cc: Oliver Upton , kvmarm@lists.linux.dev, James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] KVM: arm64: Allow userspace to change ID_AA64PFR1_EL1 In-Reply-To: References: <20240618063808.1040085-1-shahuang@redhat.com> <20240618063808.1040085-2-shahuang@redhat.com> <86ed8uk8cr.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: shahuang@redhat.com, oliver.upton@linux.dev, kvmarm@lists.linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240621_005336_732421_A2B0EF5F X-CRM114-Status: GOOD ( 31.39 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 21 Jun 2024 07:17:57 +0100, Shaoqin Huang wrote: > > Hi Marc, > > On 6/18/24 15:39, Marc Zyngier wrote: > > On Tue, 18 Jun 2024 07:38:06 +0100, > > Shaoqin Huang wrote: > >> > >> Allow userspace to change the guest-visible value of the register with > >> some severe limitation: > >> > >> - No changes to features not virtualized by KVM (MPAM_frac, RAS_frac) > >> --- > >> arch/arm64/kvm/sys_regs.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > >> index 22b45a15d068..bead81867bce 100644 > >> --- a/arch/arm64/kvm/sys_regs.c > >> +++ b/arch/arm64/kvm/sys_regs.c > >> @@ -2306,7 +2306,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { > >> ID_AA64PFR0_EL1_GIC | > >> ID_AA64PFR0_EL1_AdvSIMD | > >> ID_AA64PFR0_EL1_FP), }, > >> - ID_SANITISED(ID_AA64PFR1_EL1), > >> + ID_WRITABLE(ID_AA64PFR1_EL1, ~(ID_AA64PFR1_EL1_RAS_frac | > >> + ID_AA64PFR1_EL1_MPAM_frac)), > >> ID_UNALLOCATED(4,2), > >> ID_UNALLOCATED(4,3), > >> ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0), > > > > This isn't a valid patch. > > > > Furthermore, how about all the other features that may or may not be > > currently handled by KVM? Please see [1] and make sure that all > > existing fields have a known behaviour (a combination of masked, > > preserved, capped, writable or read-only). > > > > I can at least see problems with MTE_frac and MTEX, plus all the other > > things that KVM doesn't know how to save/restore (THE, GCS, NMI...). > > > > What I asked you to handle the whole register, I really meant it. > > I currently only found the BT and SSBS fields can be written without > any unknown behavior. I can only assume you haven't looked hard enough. > > All other fields in the ID_AA64PFR1_EL1 are either not supported by > KVM or the field involved with other register and KVM don't know how > to handle them. Why can't CSV2_frac be writable? Why can't most of the other fields be hidden depending on the VM configuration, as pointed out above? M. -- Without deviation from the norm, progress is not possible.