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Mon, 17 May 2021 18:04:29 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 86EEC61166; Mon, 17 May 2021 18:04:27 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lihbN-001uz5-NV; Mon, 17 May 2021 19:04:25 +0100 Date: Mon, 17 May 2021 19:04:24 +0100 Message-ID: <87sg2ltexj.wl-maz@kernel.org> From: Marc Zyngier To: Steven Price Cc: Catalin Marinas , 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 In-Reply-To: <20210517123239.8025-8-steven.price@arm.com> References: <20210517123239.8025-1-steven.price@arm.com> <20210517123239.8025-8-steven.price@arm.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/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: steven.price@arm.com, catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave.Martin@arm.com, mark.rutland@arm.com, tglx@linutronix.de, qemu-devel@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, richard.henderson@linaro.org, peter.maydell@linaro.org, Haibo.Xu@arm.com, drjones@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210517_110427_902238_47474E7B X-CRM114-Status: GOOD ( 33.80 ) 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, 17 May 2021 13:32:38 +0100, Steven Price wrote: > > The VMM may not wish to have it's own mapping of guest memory mapped > with PROT_MTE because this causes problems if the VMM has tag checking > enabled (the guest controls the tags in physical RAM and it's unlikely > the tags are correct for the VMM). > > Instead add a new ioctl which allows the VMM to easily read/write the > tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE > while the VMM can still read/write the tags for the purpose of > migration. > > Signed-off-by: Steven Price > --- > arch/arm64/include/uapi/asm/kvm.h | 11 +++++ > arch/arm64/kvm/arm.c | 69 +++++++++++++++++++++++++++++++ > include/uapi/linux/kvm.h | 1 + > 3 files changed, 81 insertions(+) > > 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]; > +}; > + > +#define KVM_ARM_TAGS_TO_GUEST 0 > +#define KVM_ARM_TAGS_FROM_GUEST 1 > + > /* If you need to interpret the index values, here is the key: */ > #define KVM_REG_ARM_COPROC_MASK 0x000000000FFF0000 > #define KVM_REG_ARM_COPROC_SHIFT 16 > 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; nit: this is a compile time constant, make it a #define. This will avoid the confusing overloading of "num_tags" as both an input and an output for the mte_copy_tags-* functions. > + > + 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); > + } else { > + num_tags = mte_copy_tags_from_user(maddr, tags, > + num_tags); > + kvm_release_pfn_dirty(pfn); > + } > + > + 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; > +} > + nit again: I'd really prefer it if you moved this to guest.c, where we already have a bunch of the save/restore stuff. > long kvm_arch_vm_ioctl(struct file *filp, > unsigned int ioctl, unsigned long arg) > { > @@ -1345,6 +1404,16 @@ long kvm_arch_vm_ioctl(struct file *filp, > > return 0; > } > + case KVM_ARM_MTE_COPY_TAGS: { > + struct kvm_arm_copy_mte_tags copy_tags; > + > + if (!kvm_has_mte(kvm)) > + return -EINVAL; > + > + if (copy_from_user(©_tags, argp, sizeof(copy_tags))) > + return -EFAULT; > + return kvm_vm_ioctl_mte_copy_tags(kvm, ©_tags); > + } > default: > return -EINVAL; > } > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 8c95ba0fadda..4c011c60d468 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -1428,6 +1428,7 @@ struct kvm_s390_ucas_mapping { > /* Available with KVM_CAP_PMU_EVENT_FILTER */ > #define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct kvm_pmu_event_filter) > #define KVM_PPC_SVM_OFF _IO(KVMIO, 0xb3) > +#define KVM_ARM_MTE_COPY_TAGS _IOR(KVMIO, 0xb4, struct kvm_arm_copy_mte_tags) > > /* ioctl for vm fd */ > #define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device) Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel