From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6E47F3EC2C4; Fri, 5 Jun 2026 16:18:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780676314; cv=none; b=mMVhoYxVtvfZPYP1vqWFzoCv6XEe+abIO/WFav/Wmb+wUKNbsgwi5LGSn/Dl8VO78ef5wlmALHdEBYlhLey8d9ZueO23UC3HifNvEVoicWd5F0ZeY92ME6gD9P/ZyVdtkEu1ZcfogHCFgvNR0euCh2N5mFQmxmHMjuW+1kgDDcw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780676314; c=relaxed/simple; bh=0zDnckQwo3OyEOUTc6ZFIgTkloOPTw/hoEsuIkohg7c=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=CJ+wT22rrYPceifJ5UCQlJtmoDdvlRgmRbJNu5cuoRlX7jWt46Tkh0ZMmJuiKO5NeDpQQ7pp+Utjc58pbxgUXfoRrV5UV4yBiSpiY/lnj2HXVVbPgS0qroTY/k3nMqqtDtudEjuXuQkDORWiqyxRh7DZsNWSfa2C39/lBdU/57s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KRR9fExA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KRR9fExA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36B001F00893; Fri, 5 Jun 2026 16:18:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780676313; bh=nYScoSNB3jeAjdu79Y5o8uX0JVKrcUm3yPFfVKrfJhc=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=KRR9fExACnOGFbKp94dMiMDBasEsk6vuaaszVAdHMf+gGgv7/QIltw6tLHZjGHnP6 wO+YU2JfejPZe0+Uy4MpVDCwI7AEOJwMwsQGcBFAAK7upNUS0oLkSu1JIkKu8Bq+6c UNS/k7DOurCxr6G0BSnIY5cY8Heisr9VgRdXvBdlMhZECOJNmPBmATHOQiDoUzaHtr Bb1v0mPP2vRJiiJKUiBpYH/3TVpoANdFxMHIZ/NSJDb1Dnok8xFiILJiSkxKbetLBa z9ZRymp8+cvj0BqU3J91G6j7g4gcVO6L9/P5Zd3xLE0s1UKfUF5jCZjYQ7PgObKWXf ld8GQfLdnSinw== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1wVXFf-00000009q2m-0clu; Fri, 05 Jun 2026 16:18:31 +0000 Date: Fri, 05 Jun 2026 17:18:30 +0100 Message-ID: <86wlwdt0yx.wl-maz@kernel.org> From: Marc Zyngier To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, Ard Biesheuvel , Kevin Brodsky , Mark Brown , stable@vger.kernel.org Subject: Re: [PATCH v2 4/5] KVM: arm64: Omit tag sync on stage-2 mappings of the zero page In-Reply-To: <20260604151151.150377-11-ardb+git@google.com> References: <20260604151151.150377-7-ardb+git@google.com> <20260604151151.150377-11-ardb+git@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: ardb+git@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, ardb@kernel.org, kevin.brodsky@arm.com, broonie@kernel.org, stable@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Thu, 04 Jun 2026 16:11:56 +0100, Ard Biesheuvel wrote: > > From: Ard Biesheuvel > > Commit > > f620d66af316 ("arm64: mte: Do not flag the zero page as PG_mte_tagged") > > removed the PG_mte_tagged flag from the zero page, but missed a KVM code > path that may set this flag on the zero page when it is used in a > stage-2 CoW mapping of anonymous memory. > > So disregard the zero page explicitly in sanitise_mte_tags(). > > Fixes: f620d66af316 ("arm64: mte: Do not flag the zero page as PG_mte_tagged") > Cc: # 5.10.x > Suggested-by: Catalin Marinas > Signed-off-by: Ard Biesheuvel > --- > arch/arm64/kvm/mmu.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index d089c107d9b7..445d6cf035c9 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1479,6 +1479,11 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn, > if (!kvm_has_mte(kvm)) > return; > > + if (is_zero_pfn(pfn)) { > + WARN_ON_ONCE(nr_pages != 1); > + return; > + } > + > if (folio_test_hugetlb(folio)) { > /* Hugetlb has MTE flags set on head page only */ > if (folio_try_hugetlb_mte_tagging(folio)) { Reviewed-by: Marc Zyngier M. -- Without deviation from the norm, progress is not possible.