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=-10.0 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=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 074EEC43461 for ; Fri, 4 Sep 2020 14:22:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF03820797 for ; Fri, 4 Sep 2020 14:22:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599229330; bh=6KTkxpgzQHDR1wFViFDOTk7r1crsAnUhrlDc4NUnbmE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=X5hiwFOPlyuYrYNiTblimDVoX/hniwSid4gHVPvFCM/MDeL/RP6j5qn46o1NlfLKJ 4jC3YgKxgpfnABmHkpu0a5oAu0daA7KAK8enii+jHN31KILr1oHCnV3eZHWl5EgF3g a4tyeEgctVniLzirEUPgxxSh+OWOOro9Lu+v+q0w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730529AbgIDOWH (ORCPT ); Fri, 4 Sep 2020 10:22:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:38338 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730476AbgIDNeX (ORCPT ); Fri, 4 Sep 2020 09:34:23 -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 3432B2166E; Fri, 4 Sep 2020 13:31:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599226269; bh=6KTkxpgzQHDR1wFViFDOTk7r1crsAnUhrlDc4NUnbmE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zPn+u4B9ePNx0o2SSf9VKW00FGM4iak4fYTwhWyQlISiP00VOZwKADM5bGqOFNlnv QjD25xugUtaQMoycDoSqkz8TZ1Axjytkmfgrt+ZK/SVpqPGmZqHjaAlGgrFu7Nk6WP Xyofay/lkks4ouVV9Wvc1ftKf2w3Db13SmodVKtU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, James Morse , Marc Zyngier , Catalin Marinas , Andre Przywara Subject: [PATCH 5.8 09/17] KVM: arm64: Survive synchronous exceptions caused by AT instructions Date: Fri, 4 Sep 2020 15:30:08 +0200 Message-Id: <20200904120258.449102679@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200904120257.983551609@linuxfoundation.org> References: <20200904120257.983551609@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 # 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 | 14 ++++++++++---- arch/arm64/kvm/hyp/switch.c | 8 ++++---- 3 files changed, 42 insertions(+), 8 deletions(-) --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -121,6 +121,34 @@ extern char __smccc_workaround_1_smc[__S *__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 @@ -166,13 +166,19 @@ el1_error: b __guest_exit el2_sync: - /* Check for illegal exception return, otherwise panic */ + /* Check for illegal exception return */ mrs x0, spsr_el2 + tbnz x0, #20, 1f - /* if this was something else, then panic! */ - tst x0, #PSR_IL_BIT - b.eq __hyp_panic + 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 + +1: /* Let's attempt a recovery from the illegal exception return */ get_vcpu_ptr x1, x0 mov x0, #ARM_EXCEPTION_IL --- a/arch/arm64/kvm/hyp/switch.c +++ b/arch/arm64/kvm/hyp/switch.c @@ -303,10 +303,10 @@ 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 = SYS_PAR_EL1_F; /* back to the guest */ write_sysreg(par, par_el1); if (unlikely(tmp & SYS_PAR_EL1_F))