From patchwork Thu Mar 4 21:38:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hector Martin X-Patchwork-Id: 392891 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT 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 A669AC433E9 for ; Thu, 4 Mar 2021 21:41:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F99265007 for ; Thu, 4 Mar 2021 21:41:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240106AbhCDVkV (ORCPT ); Thu, 4 Mar 2021 16:40:21 -0500 Received: from marcansoft.com ([212.63.210.85]:33250 "EHLO mail.marcansoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240093AbhCDVkQ (ORCPT ); Thu, 4 Mar 2021 16:40:16 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: hector@marcansoft.com) by mail.marcansoft.com (Postfix) with ESMTPSA id 354873FA28; Thu, 4 Mar 2021 21:39:26 +0000 (UTC) From: Hector Martin To: linux-arm-kernel@lists.infradead.org Cc: Hector Martin , Marc Zyngier , Rob Herring , Arnd Bergmann , Olof Johansson , Krzysztof Kozlowski , Mark Kettenis , Tony Lindgren , Mohamed Mediouni , Stan Skowronek , Alexander Graf , Will Deacon , Linus Walleij , Mark Rutland , Andy Shevchenko , Greg Kroah-Hartman , Jonathan Corbet , Catalin Marinas , Christoph Hellwig , "David S. Miller" , devicetree@vger.kernel.org, linux-serial@vger.kernel.org, linux-doc@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFT PATCH v3 01/27] arm64: Cope with CPUs stuck in VHE mode Date: Fri, 5 Mar 2021 06:38:36 +0900 Message-Id: <20210304213902.83903-2-marcan@marcan.st> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210304213902.83903-1-marcan@marcan.st> References: <20210304213902.83903-1-marcan@marcan.st> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org From: Marc Zyngier It seems that the CPU known as Apple M1 has 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. 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 | 28 ++++++++++++++++++++++++---- 2 files changed, 54 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 66b0e0b66e31..673002b11865 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 + +1: + mov_q x0, INIT_SCTLR_EL1_MMU_OFF + msr sctlr_el1, x0 + msr elr_el2, lr mov w0, #BOOT_CPU_MODE_EL2 eret diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S index 5eccbd62fec8..c7601030ee82 100644 --- a/arch/arm64/kernel/hyp-stub.S +++ b/arch/arm64/kernel/hyp-stub.S @@ -27,12 +27,12 @@ SYM_CODE_START(__hyp_stub_vectors) ventry el2_fiq_invalid // FIQ EL2t ventry el2_error_invalid // Error EL2t - ventry el2_sync_invalid // Synchronous EL2h + ventry elx_sync // Synchronous EL2h ventry el2_irq_invalid // IRQ EL2h ventry el2_fiq_invalid // FIQ EL2h ventry el2_error_invalid // Error EL2h - ventry el1_sync // Synchronous 64-bit EL1 + ventry elx_sync // Synchronous 64-bit EL1 ventry el1_irq_invalid // IRQ 64-bit EL1 ventry el1_fiq_invalid // FIQ 64-bit EL1 ventry el1_error_invalid // Error 64-bit EL1 @@ -45,7 +45,7 @@ SYM_CODE_END(__hyp_stub_vectors) .align 11 -SYM_CODE_START_LOCAL(el1_sync) +SYM_CODE_START_LOCAL(elx_sync) cmp x0, #HVC_SET_VECTORS b.ne 1f msr vbar_el2, x1 @@ -71,7 +71,7 @@ SYM_CODE_START_LOCAL(el1_sync) 9: mov x0, xzr eret -SYM_CODE_END(el1_sync) +SYM_CODE_END(elx_sync) // nVHE? No way! Give me the real thing! SYM_CODE_START_LOCAL(mutate_to_vhe) @@ -243,3 +243,23 @@ SYM_FUNC_START(switch_to_vhe) #endif ret SYM_FUNC_END(switch_to_vhe) + +SYM_FUNC_START(stick_to_vhe) + /* + * Make sure the switch to VHE cannot fail, by overriding the + * override. This is hilarious. + */ + adr_l x1, id_aa64mmfr1_override + add x1, x1, #FTR_OVR_MASK_OFFSET + dc civac, x1 + dsb sy + isb + ldr x0, [x1] + bic x0, x0, #(0xf << ID_AA64MMFR1_VHE_SHIFT) + str x0, [x1] + + mov x0, #HVC_VHE_RESTART + hvc #0 + mov x0, #BOOT_CPU_MODE_EL2 + ret +SYM_FUNC_END(stick_to_vhe)