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=-16.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 DCCE6C433E0 for ; Sat, 30 Jan 2021 16:24:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DC4564E0C for ; Sat, 30 Jan 2021 16:24:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231303AbhA3QYX (ORCPT ); Sat, 30 Jan 2021 11:24:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:43120 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231864AbhA3OmG (ORCPT ); Sat, 30 Jan 2021 09:42:06 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4BC3164E0F; Sat, 30 Jan 2021 14:41:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612017680; bh=FHWp0ZsnkeE/SCgjm4BWBG9iO3R5Tce7agUrvcVpBIE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=S9H1nFwH2m0JtsYmg09xdxhirPDrIX8iSFlfiOs0OlAb9sPbRY5TT7tPvFhNWMGIh g/7vY5dEbU7meUg1UMuygcIjSKPV7zPSu51WGNmIvBSiO8eWulnzW6K0icSEvrm5J2 2AEbmdNY2KI3bgacRYmPuVbXxScoudh/GmycIi6hB/m/uDKTvzWszdXLDXuF9FaZmk RcS5zXZz+YiLQqK6NlU3ERIAOuhBISjUoRIy+xPwiLRa34ATE1vQR6sQODI8X15LAV +fF0gv3GR2uW6c/C0u5HJ0mfHhqOjE8ivSRqIFUtogOg+XW2Si2c4acg2eVuG229w6 BvrCu0EvuZHmQ== Date: Sat, 30 Jan 2021 16:41:16 +0200 From: Jarkko Sakkinen To: Kai Huang Cc: linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, seanjc@google.com, luto@kernel.org, dave.hansen@intel.com, haitao.huang@intel.com, pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Subject: Re: [RFC PATCH v3 06/27] x86/sgx: Introduce virtual EPC for use by KVM guests Message-ID: References: <8492ee41e947aa8151007e5ecbd9ef8914dd8827.1611634586.git.kai.huang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8492ee41e947aa8151007e5ecbd9ef8914dd8827.1611634586.git.kai.huang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Jan 26, 2021 at 10:30:21PM +1300, Kai Huang wrote: > From: Sean Christopherson > > Add a misc device /dev/sgx_vepc to allow userspace to allocate "raw" EPC > without an associated enclave. The intended and only known use case for > raw EPC allocation is to expose EPC to a KVM guest, hence the 'vepc' > moniker, virt.{c,h} files and X86_SGX_KVM Kconfig. > > More specifically, to allocate a virtual EPC instance with particular > size, the userspace hypervisor opens the device node, and uses mmap() > with the intended size to get an address range of virtual EPC. Then > it may use the address range to create one KVM memory slot as virtual > EPC for guest. > > Implement the "raw" EPC allocation in the x86 core-SGX subsystem via > /dev/sgx_vepc rather than in KVM. Doing so has two major advantages: > > - Does not require changes to KVM's uAPI, e.g. EPC gets handled as > just another memory backend for guests. > > - EPC management is wholly contained in the SGX subsystem, e.g. SGX > does not have to export any symbols, changes to reclaim flows don't > need to be routed through KVM, SGX's dirty laundry doesn't have to > get aired out for the world to see, and so on and so forth. > > The virtual EPC pages allocated to guests are currently not reclaimable. > Reclaiming EPC page used by enclave requires a special reclaim mechanism > separate from normal page reclaim, and that mechanism is not supported > for virutal EPC pages. Due to the complications of handling reclaim > conflicts between guest and host, reclaiming virtual EPC pages is > significantly more complex than basic support for SGX virtualization. > > Signed-off-by: Sean Christopherson > Co-developed-by: Kai Huang > Signed-off-by: Kai Huang > --- > v2->v3: > > - Changed from /dev/sgx_virt_epc to /dev/sgx_vepc, per Jarkko. Accordingly, > renamed 'sgx_virt_epc_xx' to 'sgx_vepc_xx' for various functions and > structrues. > - Changed CONFIG_X86_SGX_VIRTUALIZATION to CONFIG_X86_SGX_KVM, per Dave. > > v1->v2: > > - Added one paragraph to explain fops of virtual EPC, per Jarkko's suggestion. > - Moved change to sgx_init() out of this patch to a separate patch, as stated > in cover letter. > - In sgx_virt_epc_init(), return error if VMX is not supported, or > CONFIG_KVM_INTEL is not enabled, because there's no point to create > /dev/sgx_virt_epc if KVM is not supported. > - Removed 'struct mm_struct *mm' in 'struct sgx_virt_epc', and related logic in > sgx_virt_epc_open/release/mmap(), per Dave's comment. > - Renamed 'virtual_epc_zombie_pages' and 'virt_epc_lock' to 'zombie_secs_pages' > 'zombie_secs_pages_lock', per Dave's suggestion. > - Changed __sgx_free_epc_page() to sgx_free_epc_page() due to Jarkko's patch > removes EREMOVE in sgx_free_epc_page(). > - Changed all struct sgx_virt_epc *epc to struct sgx_virt_epc *vepc. > - In __sgx_virt_epc_fault(), changed comment to use WARN_ON() to make sure > vepc->lock has already been hold, per Dave's suggestion. > - In sgx_virt_epc_free_page(), added comments to explain SGX_ENCLAVE_ACT is not > expected; and changed to use WARN_ONCE() to dump actual error code, per > Dave's comment. > - Removed NULL page check in sgx_virt_epc_free_page(), per Dave's comment. > > --- > arch/x86/Kconfig | 12 ++ > arch/x86/kernel/cpu/sgx/Makefile | 1 + > arch/x86/kernel/cpu/sgx/virt.c | 254 +++++++++++++++++++++++++++++++ > arch/x86/kernel/cpu/sgx/virt.h | 14 ++ > 4 files changed, 281 insertions(+) > create mode 100644 arch/x86/kernel/cpu/sgx/virt.c > create mode 100644 arch/x86/kernel/cpu/sgx/virt.h > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 21f851179ff0..ccb35d14c297 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1951,6 +1951,18 @@ config X86_SGX > > If unsure, say N. > > +config X86_SGX_KVM > + bool "Software Guard eXtensions (SGX) Virtualization" > + depends on X86_SGX && KVM_INTEL > + help > + > + Enables KVM guests to create SGX enclaves. > + > + This includes support to expose "raw" unreclaimable enclave memory to > + guests via a device node, e.g. /dev/sgx_vepc. > + > + If unsure, say N. > + > config EFI > bool "EFI runtime service support" > depends on ACPI > diff --git a/arch/x86/kernel/cpu/sgx/Makefile b/arch/x86/kernel/cpu/sgx/Makefile > index 91d3dc784a29..9c1656779b2a 100644 > --- a/arch/x86/kernel/cpu/sgx/Makefile > +++ b/arch/x86/kernel/cpu/sgx/Makefile > @@ -3,3 +3,4 @@ obj-y += \ > encl.o \ > ioctl.o \ > main.o > +obj-$(CONFIG_X86_SGX_KVM) += virt.o > diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c > new file mode 100644 > index 000000000000..e1ad7856d878 > --- /dev/null > +++ b/arch/x86/kernel/cpu/sgx/virt.c > @@ -0,0 +1,254 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright(c) 2016-20 Intel Corporation. */ > + > +#define pr_fmt(fmt) "SGX virtual EPC: " fmt Remove this. It's fine to use "sgx:" also for these messages and easens grepping. > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include "encls.h" > +#include "sgx.h" > +#include "virt.h" > + > +struct sgx_vepc { > + struct xarray page_array; > + struct mutex lock; > +}; > + > +static struct mutex zombie_secs_pages_lock; > +static struct list_head zombie_secs_pages; > + > +static int __sgx_vepc_fault(struct sgx_vepc *vepc, > + struct vm_area_struct *vma, unsigned long addr) > +{ > + struct sgx_epc_page *epc_page; > + unsigned long index, pfn; > + int ret; > + > + WARN_ON(!mutex_is_locked(&vepc->lock)); > + > + /* Calculate index of EPC page in virtual EPC's page_array */ > + index = vma->vm_pgoff + PFN_DOWN(addr - vma->vm_start); > + > + epc_page = xa_load(&vepc->page_array, index); > + if (epc_page) > + return 0; > + > + epc_page = sgx_alloc_epc_page(vepc, false); > + if (IS_ERR(epc_page)) > + return PTR_ERR(epc_page); > + > + ret = xa_err(xa_store(&vepc->page_array, index, epc_page, GFP_KERNEL)); > + if (ret) > + goto err_free; > + > + pfn = PFN_DOWN(sgx_get_epc_phys_addr(epc_page)); > + > + ret = vmf_insert_pfn(vma, addr, pfn); > + if (ret != VM_FAULT_NOPAGE) { > + ret = -EFAULT; > + goto err_delete; > + } > + > + return 0; > + > +err_delete: > + xa_erase(&vepc->page_array, index); > +err_free: > + sgx_free_epc_page(epc_page); > + return ret; > +} > + > +static vm_fault_t sgx_vepc_fault(struct vm_fault *vmf) > +{ > + struct vm_area_struct *vma = vmf->vma; > + struct sgx_vepc *vepc = vma->vm_private_data; > + int ret; > + > + mutex_lock(&vepc->lock); > + ret = __sgx_vepc_fault(vepc, vma, vmf->address); > + mutex_unlock(&vepc->lock); > + > + if (!ret) > + return VM_FAULT_NOPAGE; > + > + if (ret == -EBUSY && (vmf->flags & FAULT_FLAG_ALLOW_RETRY)) { > + mmap_read_unlock(vma->vm_mm); > + return VM_FAULT_RETRY; > + } > + > + return VM_FAULT_SIGBUS; > +} > + > +const struct vm_operations_struct sgx_vepc_vm_ops = { > + .fault = sgx_vepc_fault, > +}; > + > +static int sgx_vepc_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + struct sgx_vepc *vepc = file->private_data; > + > + if (!(vma->vm_flags & VM_SHARED)) > + return -EINVAL; > + > + vma->vm_ops = &sgx_vepc_vm_ops; > + /* Don't copy VMA in fork() */ > + vma->vm_flags |= VM_PFNMAP | VM_IO | VM_DONTDUMP | VM_DONTCOPY; > + vma->vm_private_data = vepc; > + > + return 0; > +} > + > +static int sgx_vepc_free_page(struct sgx_epc_page *epc_page) > +{ > + int ret; > + > + /* > + * Take a previously guest-owned EPC page and return it to the > + * general EPC page pool. > + * > + * Guests can not be trusted to have left this page in a good > + * state, so run EREMOVE on the page unconditionally. In the > + * case that a guest properly EREMOVE'd this page, a superfluous > + * EREMOVE is harmless. > + */ > + ret = __eremove(sgx_get_epc_virt_addr(epc_page)); > + if (ret) { > + /* > + * Only SGX_CHILD_PRESENT is expected, which is because of > + * EREMOVE'ing an SECS still with child, in which case it can > + * be handled by EREMOVE'ing the SECS again after all pages in > + * virtual EPC have been EREMOVE'd. See comments in below in > + * sgx_vepc_release(). > + * > + * The user of virtual EPC (KVM) needs to guarantee there's no > + * logical processor is still running in the enclave in guest, > + * otherwise EREMOVE will get SGX_ENCLAVE_ACT which cannot be > + * handled here. > + */ > + WARN_ONCE(ret != SGX_CHILD_PRESENT, > + "EREMOVE (EPC page 0x%lx): unexpected error: %d\n", > + sgx_get_epc_phys_addr(epc_page), ret); > + return ret; > + } > + > + sgx_free_epc_page(epc_page); > + return 0; > +} > + > +static int sgx_vepc_release(struct inode *inode, struct file *file) > +{ > + struct sgx_vepc *vepc = file->private_data; > + struct sgx_epc_page *epc_page, *tmp, *entry; > + unsigned long index; > + > + LIST_HEAD(secs_pages); > + > + xa_for_each(&vepc->page_array, index, entry) { > + /* > + * Remove all normal, child pages. sgx_vepc_free_page() > + * will fail if EREMOVE fails, but this is OK and expected on > + * SECS pages. Those can only be EREMOVE'd *after* all their > + * child pages. Retries below will clean them up. > + */ > + if (sgx_vepc_free_page(entry)) > + continue; > + > + xa_erase(&vepc->page_array, index); > + } > + > + /* > + * Retry EREMOVE'ing pages. This will clean up any SECS pages that > + * only had children in this 'epc' area. > + */ > + xa_for_each(&vepc->page_array, index, entry) { > + epc_page = entry; > + /* > + * An EREMOVE failure here means that the SECS page still > + * has children. But, since all children in this 'sgx_vepc' > + * have been removed, the SECS page must have a child on > + * another instance. > + */ > + if (sgx_vepc_free_page(epc_page)) > + list_add_tail(&epc_page->list, &secs_pages); > + > + xa_erase(&vepc->page_array, index); > + } > + > + /* > + * SECS pages are "pinned" by child pages, an unpinned once all > + * children have been EREMOVE'd. A child page in this instance > + * may have pinned an SECS page encountered in an earlier release(), > + * creating a zombie. Since some children were EREMOVE'd above, > + * try to EREMOVE all zombies in the hopes that one was unpinned. > + */ > + mutex_lock(&zombie_secs_pages_lock); > + list_for_each_entry_safe(epc_page, tmp, &zombie_secs_pages, list) { > + /* > + * Speculatively remove the page from the list of zombies, > + * if the page is successfully EREMOVE it will be added to > + * the list of free pages. If EREMOVE fails, throw the page > + * on the local list, which will be spliced on at the end. > + */ > + list_del(&epc_page->list); > + > + if (sgx_vepc_free_page(epc_page)) > + list_add_tail(&epc_page->list, &secs_pages); > + } > + > + if (!list_empty(&secs_pages)) > + list_splice_tail(&secs_pages, &zombie_secs_pages); > + mutex_unlock(&zombie_secs_pages_lock); > + > + kfree(vepc); > + > + return 0; > +} > + > +static int sgx_vepc_open(struct inode *inode, struct file *file) > +{ > + struct sgx_vepc *vepc; > + > + vepc = kzalloc(sizeof(struct sgx_vepc), GFP_KERNEL); > + if (!vepc) > + return -ENOMEM; > + mutex_init(&vepc->lock); > + xa_init(&vepc->page_array); > + > + file->private_data = vepc; > + > + return 0; > +} > + > +static const struct file_operations sgx_vepc_fops = { > + .owner = THIS_MODULE, > + .open = sgx_vepc_open, > + .release = sgx_vepc_release, > + .mmap = sgx_vepc_mmap, > +}; > + > +static struct miscdevice sgx_vepc_dev = { > + .minor = MISC_DYNAMIC_MINOR, > + .name = "sgx_vepc", > + .nodename = "sgx_vepc", > + .fops = &sgx_vepc_fops, > +}; > + > +int __init sgx_vepc_init(void) > +{ > + /* SGX virtualization requires KVM to work */ > + if (!boot_cpu_has(X86_FEATURE_VMX) || !IS_ENABLED(CONFIG_KVM_INTEL)) > + return -ENODEV; > + > + INIT_LIST_HEAD(&zombie_secs_pages); > + mutex_init(&zombie_secs_pages_lock); > + > + return misc_register(&sgx_vepc_dev); > +} > diff --git a/arch/x86/kernel/cpu/sgx/virt.h b/arch/x86/kernel/cpu/sgx/virt.h > new file mode 100644 > index 000000000000..44d872380ca1 > --- /dev/null > +++ b/arch/x86/kernel/cpu/sgx/virt.h > @@ -0,0 +1,14 @@ > +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */ > +#ifndef _ASM_X86_SGX_VIRT_H > +#define _ASM_X86_SGX_VIRT_H > + > +#ifdef CONFIG_X86_SGX_KVM > +int __init sgx_vepc_init(void); > +#else > +static inline int __init sgx_vepc_init(void) > +{ > + return -ENODEV; > +} > +#endif > + > +#endif /* _ASM_X86_SGX_VIRT_H */ > -- > 2.29.2 > > Other than that, this starts to be in shape. /Jarkko