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 E3032C52D6F for ; Wed, 21 Aug 2024 11:17:23 +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=iZnYpF9jenvIG4DIW9jMT1JP/7Bpffb+L1QVdvR8l+A=; b=VGbV6Gjz6YJmaSdcD0fyyoYwAh j7vVk8LoKe8knXQBlJaFU0m7HOHcyfUc3XvEwKIjbpG/xf6SX0PfkWPU3Jyux/98VE14d2oyEwaE8 GMetoOjgs/ak6SzIjcBE+mIe9RpGRxWE8r9/lFcdBo+IKxACgVQfyd08rrRzul8zLfwtXJIm7L6lP /0D5RgKEnUqWomGNuLuIMm+3D4YjRewf5j5NSPkPCHgfHTZGTJ7lBdlaBjm1mrX70qfkNcxVwFh5y 6fZUDy2On2FMMV5NEot7qAVi6oH2rhjojCtwyuDsgtmc/CgkSuTj8dsX12s3TTl8SRp343az3iRPZ lmDdaH8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sgjKz-00000008dXf-2jm8; Wed, 21 Aug 2024 11:17:13 +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 1sgjKG-00000008dMS-0yDS for linux-arm-kernel@lists.infradead.org; Wed, 21 Aug 2024 11:16:29 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 8F09760FD8; Wed, 21 Aug 2024 11:16:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 450FDC32782; Wed, 21 Aug 2024 11:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724238987; bh=PQJeXUClWIAPxChh0edfyISaZ9J1rH+OUORmO3eT5qE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FJhxJt02rS7eOjXO6WMjIA2afl2W3RPa2hQxNRh9ASYDKoNVMcShIV6R5cRGkt3A7 UC+EZUNOiBhjPQFxvUuAaJUanS14akEEfAlOXhDWA/shohcACzaxojrFiAHXnPMDJL bkhyvi4Bd3xV4T/Kw4nhtKxxIVyLT0/4tzwPh9e7GzFGGuWU3EWuc/42vdA4CYUn+E KAjolLBZ/L5444f74z1Kz4fcqUUlF6VcbGu5+Ma9jVjgG6TvHKsVkRvbo4Kq/CVo+H H37h/LYuQw/D5WiNt5p5Wxuk44T6//AYWWhsGqIqxT7P3qTrdt86gizHulSF9Jpkiu q/9SLMnEV+eag== 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 1sgjKD-005Yj5-1a; Wed, 21 Aug 2024 12:16:25 +0100 Date: Wed, 21 Aug 2024 12:16:24 +0100 Message-ID: <86h6bexh13.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, James Morse , Suzuki K Poulose , Zenghui Yu , Alexander Potapenko Subject: Re: [PATCH 06/12] KVM: arm64: Zero ID_AA64PFR0_EL1.GIC when no GICv3 is presented to the guest In-Reply-To: References: <20240820100349.3544850-1-maz@kernel.org> <20240820100349.3544850-7-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/29.4 (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: oliver.upton@linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, glider@google.com 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-20240821_041628_395299_AA7B77F5 X-CRM114-Status: GOOD ( 31.71 ) 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 Wed, 21 Aug 2024 00:50:18 +0100, Oliver Upton wrote: > > On Tue, Aug 20, 2024 at 11:03:43AM +0100, Marc Zyngier wrote: > > In order to be consistent, we shouldn't advertise a GICv3 when none > > is actually usable by the guest. > > > > Wipe the feature when these conditions apply, and allow the field > > to be written from userspace. > > > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/kvm/sys_regs.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > > index bc2d54da3827..7d00d7e359e1 100644 > > --- a/arch/arm64/kvm/sys_regs.c > > +++ b/arch/arm64/kvm/sys_regs.c > > @@ -2365,7 +2365,6 @@ static const struct sys_reg_desc sys_reg_descs[] = { > > ID_AA64PFR0_EL1_MPAM | > > ID_AA64PFR0_EL1_SVE | > > ID_AA64PFR0_EL1_RAS | > > - ID_AA64PFR0_EL1_GIC | > > ID_AA64PFR0_EL1_AdvSIMD | > > ID_AA64PFR0_EL1_FP), }, > > ID_SANITISED(ID_AA64PFR1_EL1), > > @@ -4634,6 +4633,11 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu) > > > > guard(mutex)(&kvm->arch.config_lock); > > > > + if (!kvm_has_gicv3(kvm)) { > > + kvm->arch.id_regs[IDREG_IDX(SYS_ID_AA64PFR0_EL1)] &= ~ID_AA64PFR0_EL1_GIC_MASK; > > + kvm->arch.id_regs[IDREG_IDX(SYS_ID_PFR1_EL1)] &= ~ID_PFR1_EL1_GIC_MASK; > > + } > > + > > Hmm, should we use the ID register field as the source of truth for > kvm_has_gicv3() at this point? > > I think what you have in patch #1 makes good sense for a stable > backport. Using the ID register from this point forward would make the > behavior consistent for a stupid userspace instantiated GICv3 for the VM > but clobbered it from the ID register. > > AFAICT all other usage of kvm_has_gicv3() happens after > kvm_finalize_sys_regs(), so it should take this last-minute fixup into > account. Right, so changing the definition of kvm_has_gicv3() in this patch, and using the "old" definition here only. Yup, this seems like a reasonable thing to do. Thanks, M. -- Without deviation from the norm, progress is not possible.