From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 38D6F2F0028; Wed, 16 Jul 2025 11:05:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752663956; cv=none; b=dTkXoMwH4Fw0h8CDeBxkJiRf2QttAG1rN72muXsvnsKUAgj+6Irx7wkZb4Ra9ktyMoWB/gpe3AaMueB2QZjY4rtWOnAQBQFt4M6Q7FYks7riV8yXUydqBkTqUTpHEDEcduAWgo9amG0KaOe0RDfP77DEyiLdcRmyStbTJWfdnDk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752663956; c=relaxed/simple; bh=dyQYr4lv0y7IcIYqRyjYGKZ/D0kemm9xuT47filb00c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ek02jNWo8TMzDTt56DaFQQ8J1bzQGHljEuCB2N2ccNaq5XaNU4iBkniN4zdr/9Vll/0FH4Pzzy7ec65FU3NnQB472/pCO7hqEuZvt5KeF52LqUp+QGv7krKl5hqPrcV1sB5bKT2SrP/Qb81XTq6JSlT0f0Qxk0kCeGZ2A6eyldQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 6766112FC; Wed, 16 Jul 2025 04:05:45 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 363A93F66E; Wed, 16 Jul 2025 04:05:51 -0700 (PDT) Date: Wed, 16 Jul 2025 12:05:46 +0100 From: Mark Rutland To: Andrew Donnellan Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Christian Borntraeger , Frederic Weisbecker , Heiko Carstens , Janosch Frank , Paolo Bonzini , "Paul E. McKenney" , Sven Schnelle , Vasily Gorbik , Claudio Imbrenda , Alexander Gordeev , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH 0/2] KVM: s390: Fix latent guest entry/exit bugs Message-ID: References: <20250708092742.104309-1-ajd@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250708092742.104309-1-ajd@linux.ibm.com> On Tue, Jul 08, 2025 at 07:27:40PM +1000, Andrew Donnellan wrote: > In [0], the guest_{enter,exit}_irqoff() helpers were deprecated, in favour > of guest_timing_{enter,exit}_irqoff() and > guest_context_{enter,exit}_irqoff(). This was to fix a number of latent > guest entry/exit bugs, relating to the enabling of interrupts during an > RCU extended quiescent state, instrumentation code, and correct handling > of lockdep and tracing. > > However, while arm64, mips, riscv and x86 have been migrated to the new > helpers, s390 hasn't been. There was an initial attempt at [1] to do this, > but that didn't work for reasons discussed at [2]. > > Since then, Claudio Imbrenda has reworked much of the interrupt handling. > Moving interrupt handling into vcpu_post_run() avoids the issues in [2], > so we can now move to the new helpers. Nice! > I've rebased Mark's patches from [1]. kvm-unit-tests, the kvm selftests, > and IBM's internal test suites pass under debug_defconfig. I took a quick look at this and Claudio's preparatory work, and this all looks like what I was hoping for back in one of the replies to [2]: https://lore.kernel.org/all/YerRbhqvJ5nEcQYT@FVFF77S0Q05N/ I am not aware of any additional problems, and this all looks good to me. Thanks for picking this up! Mark. > These patches do introduce some overhead - in my testing, a few of the > tests in the kvm-unit-tests exittime test suite appear 6-11% slower, but > some noticeable overhead may be unavoidable (we introduce a new function > call and the irq entry/exit paths change a bit). > > [0] https://lore.kernel.org/lkml/20220201132926.3301912-1-mark.rutland@arm.com/ > [1] https://lore.kernel.org/all/20220119105854.3160683-7-mark.rutland@arm.com/ > [2] https://lore.kernel.org/all/a4a26805-3a56-d264-0a7e-60bed1ada9f3@linux.ibm.com/ > [3] https://lore.kernel.org/all/20241022120601.167009-1-imbrenda@linux.ibm.com/ > > Mark Rutland (2): > entry: Add arch_in_rcu_eqs() > KVM: s390: Rework guest entry logic > > arch/s390/include/asm/entry-common.h | 10 ++++++ > arch/s390/include/asm/kvm_host.h | 3 ++ > arch/s390/kvm/kvm-s390.c | 51 +++++++++++++++++++++------- > arch/s390/kvm/vsie.c | 17 ++++------ > include/linux/entry-common.h | 16 +++++++++ > kernel/entry/common.c | 3 +- > 6 files changed, 77 insertions(+), 23 deletions(-) > > -- > 2.50.0