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Thu, 20 May 2021 12:06:03 +0000 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-Disposition: inline In-Reply-To: <20210517123239.8025-8-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210520_050602_328105_E4735778 X-CRM114-Status: GOOD ( 19.48 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel