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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 8BB7EC43461 for ; Tue, 8 Sep 2020 17:47:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 508872064B for ; Tue, 8 Sep 2020 17:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599587226; bh=mxuzr7O6dMz7huOoZQtTuyGVaXDwht9yY9dDSe0fT4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=E8HrQxkG5ZdtQewQbe2Xukotn5/Qgm0QKVuglXGvcp6Kywovmg1tnItoT2/RCEPFK 1bvzFMdvAlIQG4m9z+S+aGKxbDb2LMm+7pZFsrkR67fLwGRZpRpzSv/tIF302tWVjY uhuwNOOpn9s6H1RryCm3QHQ0qcwIJIjS3MybM0Rg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732109AbgIHRrB (ORCPT ); Tue, 8 Sep 2020 13:47:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:57298 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731636AbgIHQN7 (ORCPT ); Tue, 8 Sep 2020 12:13:59 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9DECC248F6; Tue, 8 Sep 2020 15:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599580396; bh=mxuzr7O6dMz7huOoZQtTuyGVaXDwht9yY9dDSe0fT4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GM2Aprrt1erolzJv17RRVz6cIyOWm+zfSVNRVBz/hD+XRS8uk87EXdR6KLPZqFb/h SBqHY8jUoTEU2I42O2yHpoa1wAAxEvSOiRv3fNfd/2+oMqKz5sZuIR7vAnSWSE3ard eqx5nv5adwkfgQvV5ZI+qSnape/oeaP5nsTVHOAU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , James Morse , Marc Zyngier , Catalin Marinas , Andre Przywara Subject: [PATCH 4.14 60/65] KVM: arm64: Survive synchronous exceptions caused by AT instructions Date: Tue, 8 Sep 2020 17:26:45 +0200 Message-Id: <20200908152220.199797070@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200908152217.022816723@linuxfoundation.org> References: <20200908152217.022816723@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: James Morse commit 88a84ccccb3966bcc3f309cdb76092a9892c0260 upstream. KVM doesn't expect any synchronous exceptions when executing, any such exception leads to a panic(). AT instructions access the guest page tables, and can cause a synchronous external abort to be taken. The arm-arm is unclear on what should happen if the guest has configured the hardware update of the access-flag, and a memory type in TCR_EL1 that does not support atomic operations. B2.2.6 "Possible implementation restrictions on using atomic instructions" from DDI0487F.a lists synchronous external abort as a possible behaviour of atomic instructions that target memory that isn't writeback cacheable, but the page table walker may behave differently. Make KVM robust to synchronous exceptions caused by AT instructions. Add a get_user() style helper for AT instructions that returns -EFAULT if an exception was generated. While KVM's version of the exception table mixes synchronous and asynchronous exceptions, only one of these can occur at each location. Re-enter the guest when the AT instructions take an exception on the assumption the guest will take the same exception. This isn't guaranteed to make forward progress, as the AT instructions may always walk the page tables, but guest execution may use the translation cached in the TLB. This isn't a problem, as since commit 5dcd0fdbb492 ("KVM: arm64: Defer guest entry when an asynchronous exception is pending"), KVM will return to the host to process IRQs allowing the rest of the system to keep running. Cc: stable@vger.kernel.org # v4.14 Signed-off-by: James Morse Reviewed-by: Marc Zyngier Signed-off-by: Catalin Marinas Signed-off-by: Andre Przywara Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/kvm_asm.h | 28 ++++++++++++++++++++++++++++ arch/arm64/kvm/hyp/hyp-entry.S | 12 ++++++++++-- arch/arm64/kvm/hyp/switch.c | 8 ++++---- 3 files changed, 42 insertions(+), 6 deletions(-) --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -83,6 +83,34 @@ extern u32 __init_stage2_translation(voi *__hyp_this_cpu_ptr(sym); \ }) +#define __KVM_EXTABLE(from, to) \ + " .pushsection __kvm_ex_table, \"a\"\n" \ + " .align 3\n" \ + " .long (" #from " - .), (" #to " - .)\n" \ + " .popsection\n" + + +#define __kvm_at(at_op, addr) \ +( { \ + int __kvm_at_err = 0; \ + u64 spsr, elr; \ + asm volatile( \ + " mrs %1, spsr_el2\n" \ + " mrs %2, elr_el2\n" \ + "1: at "at_op", %3\n" \ + " isb\n" \ + " b 9f\n" \ + "2: msr spsr_el2, %1\n" \ + " msr elr_el2, %2\n" \ + " mov %w0, %4\n" \ + "9:\n" \ + __KVM_EXTABLE(1b, 2b) \ + : "+r" (__kvm_at_err), "=&r" (spsr), "=&r" (elr) \ + : "r" (addr), "i" (-EFAULT)); \ + __kvm_at_err; \ +} ) + + #else /* __ASSEMBLY__ */ .macro hyp_adr_this_cpu reg, sym, tmp --- a/arch/arm64/kvm/hyp/hyp-entry.S +++ b/arch/arm64/kvm/hyp/hyp-entry.S @@ -207,6 +207,15 @@ el1_error: mov x0, #ARM_EXCEPTION_EL1_SERROR b __guest_exit +el2_sync: + save_caller_saved_regs_vect + stp x29, x30, [sp, #-16]! + bl kvm_unexpected_el2_exception + ldp x29, x30, [sp], #16 + restore_caller_saved_regs_vect + + eret + el2_error: save_caller_saved_regs_vect stp x29, x30, [sp, #-16]! @@ -244,7 +253,6 @@ ENDPROC(\label) invalid_vector el2t_irq_invalid invalid_vector el2t_fiq_invalid invalid_vector el2t_error_invalid - invalid_vector el2h_sync_invalid invalid_vector el2h_irq_invalid invalid_vector el2h_fiq_invalid invalid_vector el1_sync_invalid @@ -261,7 +269,7 @@ ENTRY(__kvm_hyp_vector) ventry el2t_fiq_invalid // FIQ EL2t ventry el2t_error_invalid // Error EL2t - ventry el2h_sync_invalid // Synchronous EL2h + ventry el2_sync // Synchronous EL2h ventry el2h_irq_invalid // IRQ EL2h ventry el2h_fiq_invalid // FIQ EL2h ventry el2_error // Error EL2h --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -220,10 +220,10 @@ static bool __hyp_text __translate_far_t * saved the guest context yet, and we may return early... */ par = read_sysreg(par_el1); - asm volatile("at s1e1r, %0" : : "r" (far)); - isb(); - - tmp = read_sysreg(par_el1); + if (!__kvm_at("s1e1r", far)) + tmp = read_sysreg(par_el1); + else + tmp = 1; /* back to the guest */ write_sysreg(par, par_el1); if (unlikely(tmp & 1))