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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 10AEBE77188 for ; Fri, 10 Jan 2025 14:22:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fgzunbxt/Dl7UfZi7T/9jMfP9S8v7tBKK3N7+TksBTg=; b=oE3nTZzXmVIYWR9jP2SGWMGU4v 00L1pQpYH7oY29DbJBixZWbZIIZ7+f8kTqdiJuPioC860WzcrCJzNyrWy7IK62C/a4d5F0pLYi+cH L4Ard9ZE0tODojujqk9c7gsnzFq9iDwyIz2uq87Y5aMH+5Fq8M30/Gmc6A8p0/7RBaxFIQLtlly2c 2RbXNSKfLiM/YNFOxEwBB39/UAgjrF+dTzoJlOqKHOGVFnlbBkREUxANWt9dPfT1jOr3TmPjUbAS+ mNVRmmP2eEuWn6gTo2u4Z1Fw5lUihn/WpurLaEJ6Jgb6xxBhNDnkKEz9kDF89/ZGKJZzKCC0zGK+H W37szfBA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tWFuC-0000000FcoV-0H00; Fri, 10 Jan 2025 14:22:32 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tWEnD-0000000FQ76-2V0k for linux-arm-kernel@lists.infradead.org; Fri, 10 Jan 2025 13:11:16 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 206755C106F; Fri, 10 Jan 2025 13:10:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C68A3C4CEE0; Fri, 10 Jan 2025 13:11:12 +0000 (UTC) Date: Fri, 10 Jan 2025 13:11:10 +0000 From: Catalin Marinas To: "Aneesh Kumar K.V (Arm)" Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Suzuki K Poulose , Steven Price , Will Deacon , Marc Zyngier , Mark Rutland , Oliver Upton , Joey Gouly , Zenghui Yu Subject: Re: [PATCH v2 2/7] KVM: arm64: MTE: Update code comments Message-ID: References: <20250110110023.2963795-1-aneesh.kumar@kernel.org> <20250110110023.2963795-3-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250110110023.2963795-3-aneesh.kumar@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250110_051115_687611_B15C635F X-CRM114-Status: GOOD ( 23.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jan 10, 2025 at 04:30:18PM +0530, Aneesh Kumar K.V (Arm) wrote: > commit d77e59a8fccd ("arm64: mte: Lock a page for MTE tag > initialisation") updated the locking such the kernel now allows > VM_SHARED mapping with MTE. Update the code comment to reflect this. > > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > arch/arm64/kvm/mmu.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index c9d46ad57e52..eb8220a409e1 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1391,11 +1391,11 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva) > * able to see the page's tags and therefore they must be initialised first. If > * PG_mte_tagged is set, tags have already been initialised. > * > - * The race in the test/set of the PG_mte_tagged flag is handled by: > - * - preventing VM_SHARED mappings in a memslot with MTE preventing two VMs > - * racing to santise the same page > - * - mmap_lock protects between a VM faulting a page in and the VMM performing > - * an mprotect() to add VM_MTE > + * The race in the test/set of the PG_mte_tagged flag is handled by using > + * PG_mte_lock and PG_mte_tagged together. if PG_mte_lock is found unset, we can > + * go ahead and clear the page tags. if PG_mte_lock is found set, then the page > + * tags are already cleared or there is a parallel tag clearing is going on. We ^^^^^^^^ remove this (or the other 'is') > + * wait for the parallel tag clear to finish by waiting on PG_mte_tagged bit. > */ I don't think we need to describe the behaviour of set_page_mte_tagged() and try_page_mte_tagging() in here. How the locking works for tagged pages was hidden in those functions with their own documentation. I would just remove this whole paragraph here, just leave the first one stating that the tags must be initialised if not already done so. -- Catalin