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 9879CC3DA7F for ; Wed, 7 Aug 2024 16:22:27 +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=Lk+F6+/igGZxwF9x0b1pp3AJvGJx010Pexr/Uog4Y4M=; b=IEPl4IpfnTdreyVxOd3tZeGI7W gkjQkwP6Gwhy/mxpyaba6EeezkHuB8M6MvVusP2fWdMLtZWbHINCbYzM4vu+NlM4WOVTmNk9lsuSQ eSd5oiszf+tEVKFY20FiJ58dfRS0F+BHttWzDPfo/FMGGSv/XCLkLyvDMv148H8XbzDEoZuD+Xr7R vsu/dvSabCK/BAj4h99Rvnq1soyI2rc3lzK4tAl/nQx7HLGpK4BKsbf2lqwsUDYLdsEOSQr27QXz5 WdNm1HpVC0m4Q4utMPX4rHSFOqKElumXw41zIyvE9oPEd1Z4nqm5krQJ2TLQY2x1VCbimku+SNnhw vCPmacgQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbjQW-00000005ejX-33JL; Wed, 07 Aug 2024 16:22:16 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbjPu-00000005eTl-2d2e; Wed, 07 Aug 2024 16:21:40 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 88FCBCE0C56; Wed, 7 Aug 2024 16:21:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D649C32781; Wed, 7 Aug 2024 16:21:29 +0000 (UTC) Date: Wed, 7 Aug 2024 17:21:27 +0100 From: Catalin Marinas To: Sean Christopherson Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens Subject: Re: [PATCH v12 02/84] KVM: arm64: Disallow copying MTE to guest memory while KVM is dirty logging Message-ID: References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-3-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240726235234.228822-3-seanjc@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240807_092138_900127_F301929D X-CRM114-Status: GOOD ( 17.55 ) 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, Jul 26, 2024 at 04:51:11PM -0700, Sean Christopherson wrote: > Disallow copying MTE tags to guest memory while KVM is dirty logging, as > writing guest memory without marking the gfn as dirty in the memslot could > result in userspace failing to migrate the updated page. Ideally (maybe?), > KVM would simply mark the gfn as dirty, but there is no vCPU to work with, > and presumably the only use case for copy MTE tags _to_ the guest is when > restoring state on the target. > > Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a guest") > Signed-off-by: Sean Christopherson > --- > arch/arm64/kvm/guest.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c > index e1f0ff08836a..962f985977c2 100644 > --- a/arch/arm64/kvm/guest.c > +++ b/arch/arm64/kvm/guest.c > @@ -1045,6 +1045,11 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > > mutex_lock(&kvm->slots_lock); > > + if (write && atomic_read(&kvm->nr_memslots_dirty_logging)) { > + ret = -EBUSY; > + goto out; > + } There are ways to actually log the page dirtying but I don't think it's worth it. AFAICT, reading the tags still works and that's what's used during migration (on the VM where dirty tracking takes place). Reviewed-by: Catalin Marinas