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 X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C668FC433B4 for ; Thu, 20 May 2021 12:06:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA0306108D for ; Thu, 20 May 2021 12:06:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242170AbhETMHn (ORCPT ); Thu, 20 May 2021 08:07:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:39506 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241940AbhETMHX (ORCPT ); Thu, 20 May 2021 08:07:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 07E1661059; Thu, 20 May 2021 12:05:58 +0000 (UTC) Date: Thu, 20 May 2021 13:05:56 +0100 From: Catalin Marinas To: Steven Price Cc: Marc Zyngier , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: Re: [PATCH v12 7/8] KVM: arm64: ioctl to fetch/store tags in a guest Message-ID: <20210520120556.GC12251@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-8-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210517123239.8025-8-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 17, 2021 at 01:32:38PM +0100, Steven Price wrote: > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > index 24223adae150..b3edde68bc3e 100644 > --- a/arch/arm64/include/uapi/asm/kvm.h > +++ b/arch/arm64/include/uapi/asm/kvm.h > @@ -184,6 +184,17 @@ struct kvm_vcpu_events { > __u32 reserved[12]; > }; > > +struct kvm_arm_copy_mte_tags { > + __u64 guest_ipa; > + __u64 length; > + void __user *addr; > + __u64 flags; > + __u64 reserved[2]; I forgot the past discussions, what's the reserved for? Future expansion? > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index e89a5e275e25..4b6c83beb75d 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1309,6 +1309,65 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm, > } > } > > +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > + struct kvm_arm_copy_mte_tags *copy_tags) > +{ > + gpa_t guest_ipa = copy_tags->guest_ipa; > + size_t length = copy_tags->length; > + void __user *tags = copy_tags->addr; > + gpa_t gfn; > + bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST); > + int ret = 0; > + > + if (copy_tags->reserved[0] || copy_tags->reserved[1]) > + return -EINVAL; > + > + if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST) > + return -EINVAL; > + > + if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK) > + return -EINVAL; > + > + gfn = gpa_to_gfn(guest_ipa); > + > + mutex_lock(&kvm->slots_lock); > + > + while (length > 0) { > + kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL); > + void *maddr; > + unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE; > + > + if (is_error_noslot_pfn(pfn)) { > + ret = -EFAULT; > + goto out; > + } > + > + maddr = page_address(pfn_to_page(pfn)); > + > + if (!write) { > + num_tags = mte_copy_tags_to_user(tags, maddr, num_tags); > + kvm_release_pfn_clean(pfn); Do we need to check if PG_mte_tagged is set? If the page was not faulted into the guest address space but the VMM has the page, does the gfn_to_pfn_prot() guarantee that a kvm_set_spte_gfn() was called? If not, this may read stale tags. > + } else { > + num_tags = mte_copy_tags_from_user(maddr, tags, > + num_tags); > + kvm_release_pfn_dirty(pfn); > + } Same question here, if the we can't guarantee the stage 2 pte being set, we'd need to set PG_mte_tagged. > + > + if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE) { > + ret = -EFAULT; > + goto out; > + } > + > + gfn++; > + tags += num_tags; > + length -= PAGE_SIZE; > + } > + > +out: > + mutex_unlock(&kvm->slots_lock); > + return ret; > +} > + -- Catalin