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=-15.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 27091C433DB for ; Thu, 25 Mar 2021 19:35:05 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 88CB061A31 for ; Thu, 25 Mar 2021 19:35:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 88CB061A31 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+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=desiato.20200630; 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=U3Vo8uzDgbaiQNExCV37ujQc00xIb+92vpeuGr3USVU=; b=BXxlua27SvhbVlDzG3Kehuz8o 6MoNUwI6a/8Edig7+ik5R34dIxtVLFaeXT5bjxth85qkeRaOSWBPtu7fg8lCDSCaADCER+zt9MgKH H9e3F68MkIuGPifnbH03EVBCH1Kzz1zUQLLt9MxCxmuZUf1gIzUvn14Z5ckv+Us21/bWwC41J34aa F7s6f2edUtGdUGrpvqcK2zL8JdFs7xLT2mPcR4u5LyZk0PTKFU8RGpYOndY8/cCGnvYgs6bckzPX1 vMKh3QKpqm4o/GlE6Jgxi+EU5B+NuRE6JtlKoNx39wx7yVR2oXOTUExwRUsA+9Jwh2g0AX8Rbn6XD cehI1RoTw==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lPVjV-0026Hg-KY; Thu, 25 Mar 2021 19:33:29 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lPVjQ-0026H5-WC for linux-arm-kernel@lists.infradead.org; Thu, 25 Mar 2021 19:33:26 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4254E61A31; Thu, 25 Mar 2021 19:33:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616700803; bh=FG39RmZiPQOlIBXsT8d0iYog2rpwW0CqFGvcaw3ZNUg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sG2FvRutL/6wZIqfEJslEwFvcrVMdjpWL7RPUHM1p8KxKAYtMW0woAmQTzXABVCfk gB/CifZyQP5us9yEcofAwVesq8EDd49VveGmpOsOMk/UhQ+3fuGaJuuTDNrkeUMyCm zKt4s19+o4FQvygPkUhZx4dIhMcsKoBe1xR0DZMXvwF5/N83nlk3j+rR83dqyBUNZl sf/bpA7bAQ5zTqPoPhG2AaGQm2fCSjhEE9GC8Xwjx2QPEbrQyzw4x3ikwKeYFJ1/fE csSbApkgho/jnAs9QUgx0b0rGOp7/6cGgY5Hbeqq2ANQOjaz/5U2xy1A0YnDpaPiHp 7phKWJlzovmcA== Date: Thu, 25 Mar 2021 19:33:19 +0000 From: Will Deacon To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, Hector Martin , Arnd Bergmann , Mark Rutland , Catalin Marinas , kernel-team@android.com Subject: Re: [PATCH 2/2] arm64: Cope with CPUs stuck in VHE mode Message-ID: <20210325193318.GD16123@willie-the-truck> References: <20210325124721.941182-1-maz@kernel.org> <20210325124721.941182-3-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210325124721.941182-3-maz@kernel.org> 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-20210325_193325_301459_31E4E17D X-CRM114-Status: GOOD ( 23.18 ) 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 Thu, Mar 25, 2021 at 12:47:21PM +0000, Marc Zyngier wrote: > It seems that the CPUs part of the SoC known as Apple M1 have the > terrible habit of being stuck with HCR_EL2.E2H==1, in violation > of the architecture. > > Try and work around this deplorable state of affairs by detecting > the stuck bit early and short-circuit the nVHE dance. Additional > filtering code ensures that attempts at switching to nVHE from > the command-line are also ignored. > > It is still unknown whether there are many more such nuggets > to be found... > > Reported-by: Hector Martin > Signed-off-by: Marc Zyngier > --- > arch/arm64/kernel/head.S | 33 +++++++++++++++++++++++++++--- > arch/arm64/kernel/hyp-stub.S | 15 ++++++++++---- > arch/arm64/kernel/idreg-override.c | 13 +++++++++++- > 3 files changed, 53 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 840bda1869e9..db2de5b8f3d9 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -477,14 +477,13 @@ EXPORT_SYMBOL(kimage_vaddr) > * booted in EL1 or EL2 respectively. > */ > SYM_FUNC_START(init_kernel_el) > - mov_q x0, INIT_SCTLR_EL1_MMU_OFF > - msr sctlr_el1, x0 > - > mrs x0, CurrentEL > cmp x0, #CurrentEL_EL2 > b.eq init_el2 > > SYM_INNER_LABEL(init_el1, SYM_L_LOCAL) > + mov_q x0, INIT_SCTLR_EL1_MMU_OFF > + msr sctlr_el1, x0 > isb > mov_q x0, INIT_PSTATE_EL1 > msr spsr_el1, x0 > @@ -504,6 +503,34 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL) > msr vbar_el2, x0 > isb > > + /* > + * Fruity CPUs seem to have HCR_EL2.E2H set to RES1, > + * making it impossible to start in nVHE mode. Is that > + * compliant with the architecture? Absolutely not! > + */ > + mrs x0, hcr_el2 > + and x0, x0, #HCR_E2H > + cbz x0, 1f > + > + /* Switching to VHE requires a sane SCTLR_EL1 as a start */ > + mov_q x0, INIT_SCTLR_EL1_MMU_OFF > + msr_s SYS_SCTLR_EL12, x0 > + > + /* > + * Force an eret into a helper "function", and let it return > + * to our original caller... This makes sure that we have > + * initialised the basic PSTATE state. > + */ > + mov x0, #INIT_PSTATE_EL2 > + msr spsr_el1, x0 > + adr_l x0, stick_to_vhe > + msr elr_el1, x0 > + eret What does this do if CONFIG_VHE=n on one of these CPUs? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel