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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47662C433EF for ; Wed, 19 Jan 2022 10:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353333AbiASK7F (ORCPT ); Wed, 19 Jan 2022 05:59:05 -0500 Received: from foss.arm.com ([217.140.110.172]:53402 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345368AbiASK7E (ORCPT ); Wed, 19 Jan 2022 05:59:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 83BB8ED1; Wed, 19 Jan 2022 02:59:03 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 104583F73D; Wed, 19 Jan 2022 02:58:58 -0800 (PST) From: Mark Rutland To: linux-kernel@vger.kernel.org, Paolo Bonzini , Michael Ellerman Cc: aleksandar.qemu.devel@gmail.com, alexandru.elisei@arm.com, anup.patel@wdc.com, aou@eecs.berkeley.edu, atish.patra@wdc.com, borntraeger@linux.ibm.com, bp@alien8.de, catalin.marinas@arm.com, chenhuacai@kernel.org, dave.hansen@linux.intel.com, frankja@linux.ibm.com, frederic@kernel.org, gor@linux.ibm.com, hca@linux.ibm.com, james.morse@arm.com, jmattson@google.com, joro@8bytes.org, luto@kernel.org, mark.rutland@arm.com, maz@kernel.org, mingo@redhat.com, nsaenzju@redhat.com, palmer@dabbelt.com, paulmck@kernel.org, paul.walmsley@sifive.com, peterz@infradead.org, seanjc@google.com, suzuki.poulose@arm.com, svens@linux.ibm.com, tglx@linutronix.de, tsbogend@alpha.franken.de, vkuznets@redhat.com, wanpengli@tencent.com, will@kernel.org Subject: [PATCH v2 0/7] kvm: fix latent guest entry/exit bugs Date: Wed, 19 Jan 2022 10:58:47 +0000 Message-Id: <20220119105854.3160683-1-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Several architectures have latent bugs around guest entry/exit. This series addresses those for: arm64, mips, riscv, s390, x86 However, I'm not sure how to address powerpc and could do with some help there. I have build-tested the arm64, mips, riscv, s390, and x86 cases, but I don't have a suitable HW setup to test these, so any review and/or testing would be much appreciated. Issues include: 1) Several architectures enable interrupts between guest_enter() and guest_exit(). As this period is an RCU extended quiescent state (EQS) this is unsound unless the irq entry code explicitly wakes RCU, which most architectures only do for entry from usersapce or idle. I believe this affects: arm64, riscv, s390 I am not sure about powerpc. 2) Several architectures permit instrumentation of code between guest_enter() and guest_exit(), e.g. KASAN, KCOV, KCSAN, etc. As instrumentation may directly o indirectly use RCU, this has the same problems as with interrupts. I believe this affects: arm64, mips, powerpc, riscv, s390 3) Several architectures do not inform lockdep and tracing that interrupts are enabled during the execution of the guest, or do so in an incorrect order. Generally this means that logs will report IRQs being masked for much longer than is actually the case, which is not ideal for debugging. I don't know whether this affects the correctness of lockdep. I believe this affects: arm64, mips, powerpc, riscv, s390 This was previously fixed for x86 specifically in a series of commits: 87fa7f3e98a1310e ("x86/kvm: Move context tracking where it belongs") 0642391e2139a2c1 ("x86/kvm/vmx: Add hardirq tracing to guest enter/exit") 9fc975e9efd03e57 ("x86/kvm/svm: Add hardirq tracing on guest enter/exit") 3ebccdf373c21d86 ("x86/kvm/vmx: Move guest enter/exit into .noinstr.text") 135961e0a7d555fc ("x86/kvm/svm: Move guest enter/exit into .noinstr.text") 160457140187c5fb ("KVM: x86: Defer vtime accounting 'til after IRQ handling") bc908e091b326467 ("KVM: x86: Consolidate guest enter/exit logic to common helpers") But other architectures were left broken, and the infrastructure for handling this correctly is x86-specific. This series introduces generic helper functions which can be used to handle the problems above, and migrates architectures over to these, fixing the latent issues. For s390, where the KVM guest EQS is interruptible, I've added infrastructure to wake RCU during this EQS. Since v1 [1]: * Add arch_in_rcu_eqs() * Convert s390 * Rename exit_to_guest_mode() -> guest_state_enter_irqoff() * Rename enter_from_guest_mode() -> guest_state_exit_irqoff() * Various commit message cleanups I've pushed the series (based on v5.16) to my kvm/entry-rework branch: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kvm/entry-rework git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git kvm/entry-rework ... with this version tagged as kvm-entry-rework-20210119. [1] https://lore.kernel.org/r/20220111153539.2532246-1-mark.rutland@arm.com/ Thanks, Mark. Mark Rutland (7): entry: add arch_in_rcu_eqs() kvm: add guest_state_{enter,exit}_irqoff() kvm/arm64: rework guest entry logic kvm/mips: rework guest entry logic kvm/riscv: rework guest entry logic kvm/s390: rework guest entry logic kvm/x86: rework guest entry logic arch/arm64/kvm/arm.c | 51 +++++++----- arch/mips/kvm/mips.c | 37 ++++++++- arch/riscv/kvm/vcpu.c | 44 +++++++---- arch/s390/include/asm/entry-common.h | 10 +++ arch/s390/include/asm/kvm_host.h | 3 + arch/s390/kvm/kvm-s390.c | 49 +++++++++--- arch/s390/kvm/vsie.c | 17 ++-- arch/x86/kvm/svm/svm.c | 4 +- arch/x86/kvm/vmx/vmx.c | 4 +- arch/x86/kvm/x86.c | 4 +- arch/x86/kvm/x86.h | 45 ----------- include/linux/entry-common.h | 16 ++++ include/linux/kvm_host.h | 112 ++++++++++++++++++++++++++- kernel/entry/common.c | 3 +- 14 files changed, 286 insertions(+), 113 deletions(-) -- 2.30.2