Hi Chao, On Fri, Dec 2, 2022 at 6:18 AM Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > In memory encryption usage, guest memory may be encrypted with special > key and can be accessed only by the guest itself. We call such memory > private memory. It's valueless and sometimes can cause problem to allow > userspace to access guest private memory. This new KVM memslot extension > allows guest private memory being provided through a restrictedmem > backed file descriptor(fd) and userspace is restricted to access the > bookmarked memory in the fd. > > This new extension, indicated by the new flag KVM_MEM_PRIVATE, adds two > additional KVM memslot fields restricted_fd/restricted_offset to allow > userspace to instruct KVM to provide guest memory through restricted_fd. > 'guest_phys_addr' is mapped at the restricted_offset of restricted_fd > and the size is 'memory_size'. > > The extended memslot can still have the userspace_addr(hva). When use, a > single memslot can maintain both private memory through restricted_fd > and shared memory through userspace_addr. Whether the private or shared > part is visible to guest is maintained by other KVM code. > > A restrictedmem_notifier field is also added to the memslot structure to > allow the restricted_fd's backing store to notify KVM the memory change, > KVM then can invalidate its page table entries or handle memory errors. > > Together with the change, a new config HAVE_KVM_RESTRICTED_MEM is added > and right now it is selected on X86_64 only. > > To make future maintenance easy, internally use a binary compatible > alias struct kvm_user_mem_region to handle both the normal and the > '_ext' variants. > > Co-developed-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx> > Tested-by: Fuad Tabba <tabba@xxxxxxxxxx> V9 of this patch [*] had KVM_CAP_PRIVATE_MEM, but it's not in this patch series anymore. Any reason you removed it, or is it just an omission? [*] https://lore.kernel.org/linux-mm/20221025151344.3784230-3-chao.p.peng@xxxxxxxxxxxxxxx/ Thanks, /fuad > --- > Documentation/virt/kvm/api.rst | 40 ++++++++++++++++++++++----- > arch/x86/kvm/Kconfig | 2 ++ > arch/x86/kvm/x86.c | 2 +- > include/linux/kvm_host.h | 8 ++++-- > include/uapi/linux/kvm.h | 28 +++++++++++++++++++ > virt/kvm/Kconfig | 3 +++ > virt/kvm/kvm_main.c | 49 ++++++++++++++++++++++++++++------ > 7 files changed, 114 insertions(+), 18 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index bb2f709c0900..99352170c130 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -1319,7 +1319,7 @@ yet and must be cleared on entry. > :Capability: KVM_CAP_USER_MEMORY > :Architectures: all > :Type: vm ioctl > -:Parameters: struct kvm_userspace_memory_region (in) > +:Parameters: struct kvm_userspace_memory_region(_ext) (in) > :Returns: 0 on success, -1 on error > > :: > @@ -1332,9 +1332,18 @@ yet and must be cleared on entry. > __u64 userspace_addr; /* start of the userspace allocated memory */ > }; > > + struct kvm_userspace_memory_region_ext { > + struct kvm_userspace_memory_region region; > + __u64 restricted_offset; > + __u32 restricted_fd; > + __u32 pad1; > + __u64 pad2[14]; > + }; > + > /* for kvm_memory_region::flags */ > #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) > #define KVM_MEM_READONLY (1UL << 1) > + #define KVM_MEM_PRIVATE (1UL << 2) > > This ioctl allows the user to create, modify or delete a guest physical > memory slot. Bits 0-15 of "slot" specify the slot id and this value > @@ -1365,12 +1374,29 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr > be identical. This allows large pages in the guest to be backed by large > pages in the host. > > -The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and > -KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of > -writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to > -use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it, > -to make a new slot read-only. In this case, writes to this memory will be > -posted to userspace as KVM_EXIT_MMIO exits. > +kvm_userspace_memory_region_ext struct includes all fields of > +kvm_userspace_memory_region struct, while also adds additional fields for some > +other features. See below description of flags field for more information. > +It's recommended to use kvm_userspace_memory_region_ext in new userspace code. > + > +The flags field supports following flags: > + > +- KVM_MEM_LOG_DIRTY_PAGES to instruct KVM to keep track of writes to memory > + within the slot. For more details, see KVM_GET_DIRTY_LOG ioctl. > + > +- KVM_MEM_READONLY, if KVM_CAP_READONLY_MEM allows, to make a new slot > + read-only. In this case, writes to this memory will be posted to userspace as > + KVM_EXIT_MMIO exits. > + > +- KVM_MEM_PRIVATE, if KVM_MEMORY_ATTRIBUTE_PRIVATE is supported (see > + KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES ioctl), to indicate a new slot has private > + memory backed by a file descriptor(fd) and userspace access to the fd may be > + restricted. Userspace should use restricted_fd/restricted_offset in the > + kvm_userspace_memory_region_ext to instruct KVM to provide private memory > + to guest. Userspace should guarantee not to map the same host physical address > + indicated by restricted_fd/restricted_offset to different guest physical > + addresses within multiple memslots. Failed to do this may result undefined > + behavior. > > When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of > the memory region are automatically reflected into the guest. For example, an > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > index a8e379a3afee..690cb21010e7 100644 > --- a/arch/x86/kvm/Kconfig > +++ b/arch/x86/kvm/Kconfig > @@ -50,6 +50,8 @@ config KVM > select INTERVAL_TREE > select HAVE_KVM_PM_NOTIFIER if PM > select HAVE_KVM_MEMORY_ATTRIBUTES > + select HAVE_KVM_RESTRICTED_MEM if X86_64 > + select RESTRICTEDMEM if HAVE_KVM_RESTRICTED_MEM > help > Support hosting fully virtualized guest machines using hardware > virtualization extensions. You will need a fairly recent > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 7f850dfb4086..9a07380f8d3c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -12224,7 +12224,7 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, > } > > for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > - struct kvm_userspace_memory_region m; > + struct kvm_user_mem_region m; > > m.slot = id | (i << 16); > m.flags = 0; > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index a784e2b06625..02347e386ea2 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -44,6 +44,7 @@ > > #include <asm/kvm_host.h> > #include <linux/kvm_dirty_ring.h> > +#include <linux/restrictedmem.h> > > #ifndef KVM_MAX_VCPU_IDS > #define KVM_MAX_VCPU_IDS KVM_MAX_VCPUS > @@ -585,6 +586,9 @@ struct kvm_memory_slot { > u32 flags; > short id; > u16 as_id; > + struct file *restricted_file; > + loff_t restricted_offset; > + struct restrictedmem_notifier notifier; > }; > > static inline bool kvm_slot_dirty_track_enabled(const struct kvm_memory_slot *slot) > @@ -1123,9 +1127,9 @@ enum kvm_mr_change { > }; > > int kvm_set_memory_region(struct kvm *kvm, > - const struct kvm_userspace_memory_region *mem); > + const struct kvm_user_mem_region *mem); > int __kvm_set_memory_region(struct kvm *kvm, > - const struct kvm_userspace_memory_region *mem); > + const struct kvm_user_mem_region *mem); > void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot); > void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen); > int kvm_arch_prepare_memory_region(struct kvm *kvm, > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 5d0941acb5bb..13bff963b8b0 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -103,6 +103,33 @@ struct kvm_userspace_memory_region { > __u64 userspace_addr; /* start of the userspace allocated memory */ > }; > > +struct kvm_userspace_memory_region_ext { > + struct kvm_userspace_memory_region region; > + __u64 restricted_offset; > + __u32 restricted_fd; > + __u32 pad1; > + __u64 pad2[14]; > +}; > + > +#ifdef __KERNEL__ > +/* > + * kvm_user_mem_region is a kernel-only alias of kvm_userspace_memory_region_ext > + * that "unpacks" kvm_userspace_memory_region so that KVM can directly access > + * all fields from the top-level "extended" region. > + */ > +struct kvm_user_mem_region { > + __u32 slot; > + __u32 flags; > + __u64 guest_phys_addr; > + __u64 memory_size; > + __u64 userspace_addr; > + __u64 restricted_offset; > + __u32 restricted_fd; > + __u32 pad1; > + __u64 pad2[14]; > +}; > +#endif > + > /* > * The bit 0 ~ bit 15 of kvm_memory_region::flags are visible for userspace, > * other bits are reserved for kvm internal use which are defined in > @@ -110,6 +137,7 @@ struct kvm_userspace_memory_region { > */ > #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) > #define KVM_MEM_READONLY (1UL << 1) > +#define KVM_MEM_PRIVATE (1UL << 2) > > /* for KVM_IRQ_LINE */ > struct kvm_irq_level { > diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig > index effdea5dd4f0..d605545d6dd1 100644 > --- a/virt/kvm/Kconfig > +++ b/virt/kvm/Kconfig > @@ -89,3 +89,6 @@ config KVM_XFER_TO_GUEST_WORK > > config HAVE_KVM_PM_NOTIFIER > bool > + > +config HAVE_KVM_RESTRICTED_MEM > + bool > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 7f0f5e9f2406..b882eb2c76a2 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1532,7 +1532,7 @@ static void kvm_replace_memslot(struct kvm *kvm, > } > } > > -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem) > +static int check_memory_region_flags(const struct kvm_user_mem_region *mem) > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > > @@ -1934,7 +1934,7 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id, > * Must be called holding kvm->slots_lock for write. > */ > int __kvm_set_memory_region(struct kvm *kvm, > - const struct kvm_userspace_memory_region *mem) > + const struct kvm_user_mem_region *mem) > { > struct kvm_memory_slot *old, *new; > struct kvm_memslots *slots; > @@ -2038,7 +2038,7 @@ int __kvm_set_memory_region(struct kvm *kvm, > EXPORT_SYMBOL_GPL(__kvm_set_memory_region); > > int kvm_set_memory_region(struct kvm *kvm, > - const struct kvm_userspace_memory_region *mem) > + const struct kvm_user_mem_region *mem) > { > int r; > > @@ -2050,7 +2050,7 @@ int kvm_set_memory_region(struct kvm *kvm, > EXPORT_SYMBOL_GPL(kvm_set_memory_region); > > static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm, > - struct kvm_userspace_memory_region *mem) > + struct kvm_user_mem_region *mem) > { > if ((u16)mem->slot >= KVM_USER_MEM_SLOTS) > return -EINVAL; > @@ -4698,6 +4698,33 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm) > return fd; > } > > +#define SANITY_CHECK_MEM_REGION_FIELD(field) \ > +do { \ > + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \ > + offsetof(struct kvm_userspace_memory_region, field)); \ > + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \ > + sizeof_field(struct kvm_userspace_memory_region, field)); \ > +} while (0) > + > +#define SANITY_CHECK_MEM_REGION_EXT_FIELD(field) \ > +do { \ > + BUILD_BUG_ON(offsetof(struct kvm_user_mem_region, field) != \ > + offsetof(struct kvm_userspace_memory_region_ext, field)); \ > + BUILD_BUG_ON(sizeof_field(struct kvm_user_mem_region, field) != \ > + sizeof_field(struct kvm_userspace_memory_region_ext, field)); \ > +} while (0) > + > +static void kvm_sanity_check_user_mem_region_alias(void) > +{ > + SANITY_CHECK_MEM_REGION_FIELD(slot); > + SANITY_CHECK_MEM_REGION_FIELD(flags); > + SANITY_CHECK_MEM_REGION_FIELD(guest_phys_addr); > + SANITY_CHECK_MEM_REGION_FIELD(memory_size); > + SANITY_CHECK_MEM_REGION_FIELD(userspace_addr); > + SANITY_CHECK_MEM_REGION_EXT_FIELD(restricted_offset); > + SANITY_CHECK_MEM_REGION_EXT_FIELD(restricted_fd); > +} > + > static long kvm_vm_ioctl(struct file *filp, > unsigned int ioctl, unsigned long arg) > { > @@ -4721,14 +4748,20 @@ static long kvm_vm_ioctl(struct file *filp, > break; > } > case KVM_SET_USER_MEMORY_REGION: { > - struct kvm_userspace_memory_region kvm_userspace_mem; > + struct kvm_user_mem_region mem; > + unsigned long size = sizeof(struct kvm_userspace_memory_region); > + > + kvm_sanity_check_user_mem_region_alias(); > > r = -EFAULT; > - if (copy_from_user(&kvm_userspace_mem, argp, > - sizeof(kvm_userspace_mem))) > + if (copy_from_user(&mem, argp, size)) > + goto out; > + > + r = -EINVAL; > + if (mem.flags & KVM_MEM_PRIVATE) > goto out; > > - r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem); > + r = kvm_vm_ioctl_set_memory_region(kvm, &mem); > break; > } > case KVM_GET_DIRTY_LOG: { > -- > 2.25.1 >
