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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69914C433EF for ; Mon, 18 Oct 2021 09:06:06 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 315166054F for ; Mon, 18 Oct 2021 09:06:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 315166054F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Cc:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=l3ZEABDlGZ14dB8RFfhqmtGMNx+RHFzcwO2SW5PZ9G0=; b=42uzKM2PU97f13J0hfeE+qeeLd tG6+9XheEPxrFdOzapakeJ51bn+76LoLUKYVE6c0M5lltKxJvXd3ro00IVRJf3ArLuoSOX38EC7je P2VY0ZWVBF3wrR2EYvEsTP6m3ODxpcNcc/gjiYl7jp91FLdavyFxGSwFi6+PdmEcU9lnBDEJJJT2L P+kt+NvzCQJYHpJl4ZCrrmQ/HFGgoL/IouYJvzmwTa/8yCiOsVt/rrRS302Klnd/rr7eAzcn3SN2t tXBAyHMbpTs8hSvmUe1a+rOCibf4RIab9J/0Y+KIHrIdBMJarLakn95rNCPwsJ8UPl3ELc5w2GPil ATPA0ORQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mcOZd-00Ejkt-Fq; Mon, 18 Oct 2021 09:04:49 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mcOZa-00Ejk9-4r for linux-arm-kernel@lists.infradead.org; Mon, 18 Oct 2021 09:04:48 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 73917101E; Mon, 18 Oct 2021 02:04:40 -0700 (PDT) Received: from [10.57.25.70] (unknown [10.57.25.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 508933F70D; Mon, 18 Oct 2021 02:04:39 -0700 (PDT) Subject: Re: [RFC PATCH v4 02/39] KVM: arm64: Add lock/unlock memslot user API To: Alexandru Elisei , maz@kernel.org, james.morse@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, will@kernel.org, linux-kernel@vger.kernel.org References: <20210825161815.266051-1-alexandru.elisei@arm.com> <20210825161815.266051-3-alexandru.elisei@arm.com> From: Suzuki K Poulose Message-ID: <480ab754-dd07-1f24-4721-ccfdf0991d53@arm.com> Date: Mon, 18 Oct 2021 10:04:37 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20210825161815.266051-3-alexandru.elisei@arm.com> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211018_020446_323688_F868039C X-CRM114-Status: GOOD ( 38.05 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 25/08/2021 17:17, Alexandru Elisei wrote: > Stage 2 faults triggered by the profiling buffer attempting to write to > memory are reported by the SPE hardware by asserting a buffer management > event interrupt. Interrupts are by their nature asynchronous, which means > that the guest might have changed its stage 1 translation tables since the > attempted write. SPE reports the guest virtual address that caused the data > abort, not the IPA, which means that KVM would have to walk the guest's > stage 1 tables to find the IPA. Using the AT instruction to walk the > guest's tables in hardware is not an option because it doesn't report the > IPA in the case of a stage 2 fault on a stage 1 table walk. > > Avoid both issues by pre-mapping the guest memory at stage 2. This is being > done by adding a capability that allows the user to pin the memory backing > a memslot. The same capability can be used to unlock a memslot, which > unpins the pages associated with the memslot, but doesn't unmap the IPA > range from stage 2; in this case, the addresses will be unmapped from stage > 2 via the MMU notifiers when the process' address space changes. > > For now, the capability doesn't actually do anything other than checking > that the usage is correct; the memory operations will be added in future > patches. > > Signed-off-by: Alexandru Elisei > --- > Documentation/virt/kvm/api.rst | 56 +++++++++++++++++++++++ > arch/arm64/include/asm/kvm_mmu.h | 3 ++ > arch/arm64/kvm/arm.c | 42 ++++++++++++++++-- > arch/arm64/kvm/mmu.c | 76 ++++++++++++++++++++++++++++++++ > include/uapi/linux/kvm.h | 8 ++++ > 5 files changed, 181 insertions(+), 4 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index dae68e68ca23..741327ef06b0 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6682,6 +6682,62 @@ MAP_SHARED mmap will result in an -EINVAL return. > When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to > perform a bulk copy of tags to/from the guest. > > +7.29 KVM_CAP_ARM_LOCK_USER_MEMORY_REGION > +---------------------------------------- > + > +:Architectures: arm64 > +:Target: VM > +:Parameters: flags is one of KVM_ARM_LOCK_USER_MEMORY_REGION_FLAGS_LOCK or > + KVM_ARM_LOCK_USER_MEMORY_REGION_FLAGS_UNLOCK > + args[0] is the slot number > + args[1] specifies the permisions when the memslot is locked or if > + all memslots should be unlocked > + > +The presence of this capability indicates that KVM supports locking the memory > +associated with the memslot, and unlocking a previously locked memslot. > + > +The 'flags' parameter is defined as follows: > + > +7.29.1 KVM_ARM_LOCK_USER_MEMORY_REGION_FLAGS_LOCK > +------------------------------------------------- > + > +:Capability: 'flags' parameter to KVM_CAP_ARM_LOCK_USER_MEMORY_REGION > +:Architectures: arm64 > +:Target: VM > +:Parameters: args[0] contains the memory slot number > + args[1] contains the permissions for the locked memory: > + KVM_ARM_LOCK_MEMORY_READ (mandatory) to map it with > + read permissions and KVM_ARM_LOCK_MEMORY_WRITE > + (optional) with write permissions > +:Returns: 0 on success; negative error code on failure > + > +Enabling this capability causes the memory described by the memslot to be > +pinned in the process address space and the corresponding stage 2 IPA range > +mapped at stage 2. The permissions specified in args[1] apply to both > +mappings. The memory pinned with this capability counts towards the max > +locked memory limit for the current process. > + > +The capability must be enabled before any VCPUs have run. The virtual memory > +range described by the memslot must be mapped in the userspace process without > +any gaps. It is considered an error if write permissions are specified for a > +memslot which logs dirty pages. > + > +7.29.2 KVM_ARM_LOCK_USER_MEMORY_REGION_FLAGS_UNLOCK > +--------------------------------------------------- > + > +:Capability: 'flags' parameter to KVM_CAP_ARM_LOCK_USER_MEMORY_REGION > +:Architectures: arm64 > +:Target: VM > +:Parameters: args[0] contains the memory slot number > + args[1] optionally contains the flag KVM_ARM_UNLOCK_MEM_ALL, > + which unlocks all previously locked memslots. > +:Returns: 0 on success; negative error code on failure > + > +Enabling this capability causes the memory pinned when locking the memslot > +specified in args[0] to be unpinned, or, optionally, the memory associated > +with all locked memslots, to be unpinned. The IPA range is not unmapped > +from stage 2. > + > 8. Other capabilities. > ====================== > > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h > index b52c5c4b9a3d..ef079b5eb475 100644 > --- a/arch/arm64/include/asm/kvm_mmu.h > +++ b/arch/arm64/include/asm/kvm_mmu.h > @@ -216,6 +216,9 @@ static inline void __invalidate_icache_guest_page(void *va, size_t size) > void kvm_set_way_flush(struct kvm_vcpu *vcpu); > void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled); > > +int kvm_mmu_lock_memslot(struct kvm *kvm, u64 slot, u64 flags); > +int kvm_mmu_unlock_memslot(struct kvm *kvm, u64 slot, u64 flags); > + > static inline unsigned int kvm_get_vmid_bits(void) > { > int reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1); > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index ddace63528f1..57ac97b30b3d 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -80,16 +80,43 @@ int kvm_arch_check_processor_compat(void *opaque) > return 0; > } > > +static int kvm_arm_lock_memslot_supported(void) > +{ > + return 0; > +} > + > +static int kvm_lock_user_memory_region_ioctl(struct kvm *kvm, > + struct kvm_enable_cap *cap) > +{ > + u64 slot, flags; > + u32 action; > + > + if (cap->args[2] || cap->args[3]) > + return -EINVAL; > + > + slot = cap->args[0]; > + flags = cap->args[1]; nit: ^^ Please could we rename "flags" => "perm" (ission) ? > + action = cap->flags; We already have cap->flags, and using arg[1] as flags ( which indeed is permission by definition) is confusing. Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel