| Message ID | 8492ee41e947aa8151007e5ecbd9ef8914dd8827.1611634586.git.kai.huang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM SGX virtualization support | expand |
I'd also like to see some comments about code sharing between this and the main driver. For instance, this *could* try to share 99% of the ->fault function. Why doesn't it? I'm sure there's a good reason. > 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 Does this actually get used anywhere? Also, isn't this a bit long? Maybe: #define pr_fmt(fmt) "sgx/virt: " fmt Also, a one-line summary about what's in here would be nice next to the copyright (which needs to be updated). /* * Device driver to expose SGX enclave memory to KVM guests. * * Copyright(c) 2016-20 Intel Corporation. */ > +#include <linux/miscdevice.h> > +#include <linux/mm.h> > +#include <linux/mman.h> > +#include <linux/sched/mm.h> > +#include <linux/sched/signal.h> > +#include <linux/slab.h> > +#include <linux/xarray.h> > +#include <asm/sgx.h> > +#include <uapi/asm/sgx.h> > + > +#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; Comments would be nice for this random lock and list. The main core functions (fault, etc...) are looking OK to me. ... > +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; Can this even be built without IS_ENABLED(CONFIG_KVM_INTEL)? > + 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 */ Is more going to go in this header? It's a little sparse as-is.
On Tue, 26 Jan 2021 08:19:25 -0800 Dave Hansen wrote: > I'd also like to see some comments about code sharing between this and > the main driver. For instance, this *could* try to share 99% of the > ->fault function. Why doesn't it? I'm sure there's a good reason. > > > 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 > > Does this actually get used anywhere? Also, isn't this a bit long? Maybe: > > #define pr_fmt(fmt) "sgx/virt: " fmt It is not used. My bad. I'll remove it. And yes "sgx/virt: " is better. > > Also, a one-line summary about what's in here would be nice next to the > copyright (which needs to be updated). > > /* > * Device driver to expose SGX enclave memory to KVM guests. > * > * Copyright(c) 2016-20 Intel Corporation. > */ Will do. However the year should not be 2016-20, but should be 2021, right? I think it has been ignored since the day Sean wrote the file. > > > > +#include <linux/miscdevice.h> > > +#include <linux/mm.h> > > +#include <linux/mman.h> > > +#include <linux/sched/mm.h> > > +#include <linux/sched/signal.h> > > +#include <linux/slab.h> > > +#include <linux/xarray.h> > > +#include <asm/sgx.h> > > +#include <uapi/asm/sgx.h> > > + > > +#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; > > Comments would be nice for this random lock and list. > > The main core functions (fault, etc...) are looking OK to me. Thanks. How about below comment? /* * List to temporarily hold SECS pages that cannot be EREMOVE'd due to * having child in other virtual EPC instances, and the lock to protect it. */ > > ... > > +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; > > Can this even be built without IS_ENABLED(CONFIG_KVM_INTEL)? I think no. Thanks. I'll remove IS_ENABLED(CONFIG_KVM_INTEL). > > > + 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 */ > > Is more going to go in this header? It's a little sparse as-is. No there's no more. The sgx_vepc_init() function declaration needs to be here since sgx/main.c needs to use it. May I know your suggestion?
On 1/26/21 4:16 PM, Kai Huang wrote: > On Tue, 26 Jan 2021 08:19:25 -0800 Dave Hansen wrote: >> Also, a one-line summary about what's in here would be nice next to the >> copyright (which needs to be updated). >> >> /* >> * Device driver to expose SGX enclave memory to KVM guests. >> * >> * Copyright(c) 2016-20 Intel Corporation. >> */ > > Will do. However the year should not be 2016-20, but should be 2021, right? > > I think it has been ignored since the day Sean wrote the file. Yes, should be 2021. Also, there shouldn't be *ANY* parts of these files which you, the submitter and newly-minted effective maintainer, have ignored. It sounds like you owe us some homework to give every line of these a once-over. ... >>> +struct sgx_vepc { >>> + struct xarray page_array; >>> + struct mutex lock; >>> +}; >>> + >>> +static struct mutex zombie_secs_pages_lock; >>> +static struct list_head zombie_secs_pages; >> >> Comments would be nice for this random lock and list. >> >> The main core functions (fault, etc...) are looking OK to me. > > Thanks. How about below comment? > > /* > * List to temporarily hold SECS pages that cannot be EREMOVE'd due to > * having child in other virtual EPC instances, and the lock to protect it. > */ Fine. It's just a bit silly to say that it's a list. It's also not so temporary. Pages can live on here forever. >>> + 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 */ >> >> Is more going to go in this header? It's a little sparse as-is. > > No there's no more. The sgx_vepc_init() function declaration needs to be here > since sgx/main.c needs to use it. > > May I know your suggestion? I'd toss it in some other existing header that has more meat in it. I'm lazy.
On Tue, 26 Jan 2021 16:27:25 -0800 Dave Hansen wrote: > On 1/26/21 4:16 PM, Kai Huang wrote: > > On Tue, 26 Jan 2021 08:19:25 -0800 Dave Hansen wrote: > >> Also, a one-line summary about what's in here would be nice next to the > >> copyright (which needs to be updated). > >> > >> /* > >> * Device driver to expose SGX enclave memory to KVM guests. > >> * > >> * Copyright(c) 2016-20 Intel Corporation. > >> */ > > > > Will do. However the year should not be 2016-20, but should be 2021, right? > > > > I think it has been ignored since the day Sean wrote the file. > > Yes, should be 2021. Also, there shouldn't be *ANY* parts of these > files which you, the submitter and newly-minted effective maintainer, > have ignored. Yes agreed. > > It sounds like you owe us some homework to give every line of these a > once-over. I'll also check other files. Thanks. > > ... > >>> +struct sgx_vepc { > >>> + struct xarray page_array; > >>> + struct mutex lock; > >>> +}; > >>> + > >>> +static struct mutex zombie_secs_pages_lock; > >>> +static struct list_head zombie_secs_pages; > >> > >> Comments would be nice for this random lock and list. > >> > >> The main core functions (fault, etc...) are looking OK to me. > > > > Thanks. How about below comment? > > > > /* > > * List to temporarily hold SECS pages that cannot be EREMOVE'd due to > > * having child in other virtual EPC instances, and the lock to protect it. > > */ > > Fine. It's just a bit silly to say that it's a list. It's also not so > temporary. Pages can live on here forever. I'll remove the 'List': /* SECS pages that cannot be EREMOVE'd due to... */ The list should be empty after VM's all virtual EPC instances have been released. If one page lives in list forever, the WARN_ONCE() in sgx_vepc_free_page() will catch it, and there's bug here. > > >>> + 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 */ > >> > >> Is more going to go in this header? It's a little sparse as-is. > > > > No there's no more. The sgx_vepc_init() function declaration needs to be here > > since sgx/main.c needs to use it. > > > > May I know your suggestion? > > I'd toss it in some other existing header that has more meat in it. I'm > lazy. > I can put it into arch/x86/kernel/cpu/sgx/sgx.h, if it is good to you.
On Tue, Jan 26, 2021 at 10:30:21PM +1300, Kai Huang wrote: > From: Sean Christopherson <sean.j.christopherson@intel.com> > > 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 <sean.j.christopherson@intel.com> > Co-developed-by: Kai Huang <kai.huang@intel.com> > Signed-off-by: Kai Huang <kai.huang@intel.com> > --- > 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 <linux/miscdevice.h> > +#include <linux/mm.h> > +#include <linux/mman.h> > +#include <linux/sched/mm.h> > +#include <linux/sched/signal.h> > +#include <linux/slab.h> > +#include <linux/xarray.h> > +#include <asm/sgx.h> > +#include <uapi/asm/sgx.h> > + > +#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
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 + +#include <linux/miscdevice.h> +#include <linux/mm.h> +#include <linux/mman.h> +#include <linux/sched/mm.h> +#include <linux/sched/signal.h> +#include <linux/slab.h> +#include <linux/xarray.h> +#include <asm/sgx.h> +#include <uapi/asm/sgx.h> + +#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 */