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 B8FA6C433EF for ; Mon, 29 Nov 2021 13:09:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377530AbhK2NMf (ORCPT ); Mon, 29 Nov 2021 08:12:35 -0500 Received: from foss.arm.com ([217.140.110.172]:38494 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377463AbhK2NK2 (ORCPT ); Mon, 29 Nov 2021 08:10:28 -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 5B3B311D4; Mon, 29 Nov 2021 05:07:10 -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 0AFB83F766; Mon, 29 Nov 2021 05:07:06 -0800 (PST) From: Mark Rutland To: linux-kernel@vger.kernel.org Cc: benh@kernel.crashing.org, boqun.feng@gmail.com, bp@alien8.de, catalin.marinas@arm.com, dvyukov@google.com, efuller@redhat.com, elver@google.com, ink@jurassic.park.msu.ru, jonas@southpole.se, juri.lelli@redhat.com, linux@armlinux.org.uk, luto@kernel.org, mark.rutland@arm.com, mattst88@gmail.com, michal.simek@xilinx.com, mingo@redhat.com, mpe@ellerman.id.au, npiggin@gmail.com, paulmck@kernel.org, paulus@samba.org, peterz@infradead.org, rth@twiddle.net, shorne@gmail.com, stefan.kristiansson@saunalahti.fi, tglx@linutronix.de, vincent.guittot@linaro.org, will@kernel.org Subject: [PATCH v8 02/11] entry: snapshot thread flags Date: Mon, 29 Nov 2021 13:06:44 +0000 Message-Id: <20211129130653.2037928-3-mark.rutland@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211129130653.2037928-1-mark.rutland@arm.com> References: <20211129130653.2037928-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race. To avoid such issues, a snapshot of the flags has to be taken prior to using them. Some places already use READ_ONCE() for that, others do not. Convert them all to the new flag accessor helpers. Signed-off-by: Mark Rutland Acked-by: Paul E. McKenney Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Thomas Gleixner --- include/linux/entry-kvm.h | 2 +- kernel/entry/common.c | 4 ++-- kernel/entry/kvm.c | 4 ++-- 3 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h index 0d7865a0731c..07c878d6e323 100644 --- a/include/linux/entry-kvm.h +++ b/include/linux/entry-kvm.h @@ -75,7 +75,7 @@ static inline void xfer_to_guest_mode_prepare(void) */ static inline bool __xfer_to_guest_mode_work_pending(void) { - unsigned long ti_work = READ_ONCE(current_thread_info()->flags); + unsigned long ti_work = read_thread_flags(); return !!(ti_work & XFER_TO_GUEST_MODE_WORK); } diff --git a/kernel/entry/common.c b/kernel/entry/common.c index d5a61d565ad5..bad713684c2e 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -187,7 +187,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, /* Check if any of the above work has queued a deferred wakeup */ tick_nohz_user_enter_prepare(); - ti_work = READ_ONCE(current_thread_info()->flags); + ti_work = read_thread_flags(); } /* Return the latest work state for arch_exit_to_user_mode() */ @@ -196,7 +196,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, static void exit_to_user_mode_prepare(struct pt_regs *regs) { - unsigned long ti_work = READ_ONCE(current_thread_info()->flags); + unsigned long ti_work = read_thread_flags(); lockdep_assert_irqs_disabled(); diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c index 49972ee99aff..96d476e06c77 100644 --- a/kernel/entry/kvm.c +++ b/kernel/entry/kvm.c @@ -26,7 +26,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) if (ret) return ret; - ti_work = READ_ONCE(current_thread_info()->flags); + ti_work = read_thread_flags(); } while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched()); return 0; } @@ -43,7 +43,7 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu) * disabled in the inner loop before going into guest mode. No need * to disable interrupts here. */ - ti_work = READ_ONCE(current_thread_info()->flags); + ti_work = read_thread_flags(); if (!(ti_work & XFER_TO_GUEST_MODE_WORK)) return 0; -- 2.30.2