From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1DE31D6DDA; Mon, 28 Oct 2024 12:47:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730119658; cv=none; b=g+hRRE38qCkz81+hBJkTcpzdjwnF8JsqJHjQX/kcZ9nlujW1CMpOD6FjECWW4novrpFoFFdGLROhnc2jLEz5u2AG2e/Gl030VKY62qP8j66JExA3rWZTf8Pt749no13/rv1ZAS55GmVDJnAn7EtnAKA9lbZTnftTFThqhgW3c1I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730119658; c=relaxed/simple; bh=OlZRFoq/d2AxHvHoLmuiflTglaY8xpIsCiBPVNVcTJI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=B9sfh4WVtQP3VV63H+aRmLjW7PJF7tvAATalM+b7VrKlWU0Hy0MosaSOCrmPT4spzt3+uZQV1IT99Amrxfgk7PJPBM+MsKzuhjmuQxaL037YRlGt0+t8saBgs7GXRMpGvwon0xhJooligTv+TUmnFLt3pKulM1ZhnaDeUmqV0Ys= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XgEqUa8h; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XgEqUa8h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5529BC4CEC3; Mon, 28 Oct 2024 12:47:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730119658; bh=OlZRFoq/d2AxHvHoLmuiflTglaY8xpIsCiBPVNVcTJI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=XgEqUa8ho42bb+yGuEH9XkK4eQ9oawObnaYQ3J0+IZvXG3ToTEigom2v9XbI+d6vy xYQ4vHIt4IYi1Ksh39GYV77uXOYz85aZ6jNU+OWk6pHfDB7n2JfgjkouF6ofaaIYsF 3DmWhoIwwlhDRSMJnFhJgiSYQOKZ1gyvAoy5THY3hrTM4nCJjTtExvQJP3a7bUT88b KRZA8e6CDinrPSPidQib2chsGbcvivIeelaa5WIkqDPDdtKZPwzWjqtpIXl5n7pwzx Zwr4w9QCEfUecTACLN3WnN+9ont9VpdWNGxQpFtKImVKYe5he04xL0d4ueIv7Doyod j4t6juMe+uiwQ== X-Mailer: emacs 31.0.50 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Marc Zyngier Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Suzuki K Poulose , Steven Price , Will Deacon , Catalin Marinas , Mark Rutland , Oliver Upton , Joey Gouly , Zenghui Yu Subject: Re: [PATCH 3/4] arm64: mte: update code comments In-Reply-To: <87plnktt2q.wl-maz@kernel.org> References: <20241028094014.2596619-1-aneesh.kumar@kernel.org> <20241028094014.2596619-4-aneesh.kumar@kernel.org> <87plnktt2q.wl-maz@kernel.org> Date: Mon, 28 Oct 2024 18:17:30 +0530 Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi Marc, Thanks for reviewing the changes. Marc Zyngier writes: > On Mon, 28 Oct 2024 09:40:13 +0000, > "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 | 12 ++++++------ >> 1 file changed, 6 insertions(+), 6 deletions(-) > > This is a KVM patch. Please make sure you write the subject > accordingly, matching the existing conventions (in this case, this > should read something like: "KVM: arm64: MTE: Update..."). > Will update > >> >> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c >> index a509b63bd4dd..b5824e93cee0 100644 >> --- a/arch/arm64/kvm/mmu.c >> +++ b/arch/arm64/kvm/mmu.c >> @@ -1390,11 +1390,8 @@ 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. > > How? This comment is pretty content-free. TO be useful, you should > elaborate on *how* these two are used together. > I will add more details described in commit d77e59a8fccde7fb5dd8c57594ed147b4291c970 Should i quote the commit there in the comment? > >> */ >> static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn, >> unsigned long size) >> @@ -1646,7 +1643,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> } >> >> if (!fault_is_perm && !device && kvm_has_mte(kvm)) { >> - /* Check the VMM hasn't introduced a new disallowed VMA */ >> + /* >> + * not a permission fault implies a translation fault which >> + * means mapping the page for the first time > > How about an Access fault due to page ageing? > IIUC access fault is already handled by the caller kvm_handle_guest_abort? I can add that as part of the updated comments? -aneesh