On Tue, Dec 06, 2022 at 03:07:27PM +0000, Fuad Tabba wrote: > Hi, > > On Fri, Dec 2, 2022 at 6:18 AM Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > > > In confidential computing usages, whether a page is private or shared is > > necessary information for KVM to perform operations like page fault > > handling, page zapping etc. There are other potential use cases for > > per-page memory attributes, e.g. to make memory read-only (or no-exec, > > or exec-only, etc.) without having to modify memslots. > > > > Introduce two ioctls (advertised by KVM_CAP_MEMORY_ATTRIBUTES) to allow > > userspace to operate on the per-page memory attributes. > > - KVM_SET_MEMORY_ATTRIBUTES to set the per-page memory attributes to > > a guest memory range. > > - KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to return the KVM supported > > memory attributes. > > > > KVM internally uses xarray to store the per-page memory attributes. > > > > Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > > Link: https://lore.kernel.org/all/Y2WB48kD0J4VGynX@xxxxxxxxxx/ > > --- > > Documentation/virt/kvm/api.rst | 63 ++++++++++++++++++++++++++++ > > arch/x86/kvm/Kconfig | 1 + > > include/linux/kvm_host.h | 3 ++ > > include/uapi/linux/kvm.h | 17 ++++++++ > > virt/kvm/Kconfig | 3 ++ > > virt/kvm/kvm_main.c | 76 ++++++++++++++++++++++++++++++++++ > > 6 files changed, 163 insertions(+) > > > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > > index 5617bc4f899f..bb2f709c0900 100644 > > --- a/Documentation/virt/kvm/api.rst > > +++ b/Documentation/virt/kvm/api.rst > > @@ -5952,6 +5952,59 @@ delivery must be provided via the "reg_aen" struct. > > The "pad" and "reserved" fields may be used for future extensions and should be > > set to 0s by userspace. > > > > +4.138 KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES > > +----------------------------------------- > > + > > +:Capability: KVM_CAP_MEMORY_ATTRIBUTES > > +:Architectures: x86 > > +:Type: vm ioctl > > +:Parameters: u64 memory attributes bitmask(out) > > +:Returns: 0 on success, <0 on error > > + > > +Returns supported memory attributes bitmask. Supported memory attributes will > > +have the corresponding bits set in u64 memory attributes bitmask. > > + > > +The following memory attributes are defined:: > > + > > + #define KVM_MEMORY_ATTRIBUTE_READ (1ULL << 0) > > + #define KVM_MEMORY_ATTRIBUTE_WRITE (1ULL << 1) > > + #define KVM_MEMORY_ATTRIBUTE_EXECUTE (1ULL << 2) > > + #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) > > + > > +4.139 KVM_SET_MEMORY_ATTRIBUTES > > +----------------------------------------- > > + > > +:Capability: KVM_CAP_MEMORY_ATTRIBUTES > > +:Architectures: x86 > > +:Type: vm ioctl > > +:Parameters: struct kvm_memory_attributes(in/out) > > +:Returns: 0 on success, <0 on error > > + > > +Sets memory attributes for pages in a guest memory range. Parameters are > > +specified via the following structure:: > > + > > + struct kvm_memory_attributes { > > + __u64 address; > > + __u64 size; > > + __u64 attributes; > > + __u64 flags; > > + }; > > + > > +The user sets the per-page memory attributes to a guest memory range indicated > > +by address/size, and in return KVM adjusts address and size to reflect the > > +actual pages of the memory range have been successfully set to the attributes. > > +If the call returns 0, "address" is updated to the last successful address + 1 > > +and "size" is updated to the remaining address size that has not been set > > +successfully. The user should check the return value as well as the size to > > +decide if the operation succeeded for the whole range or not. The user may want > > +to retry the operation with the returned address/size if the previous range was > > +partially successful. > > + > > +Both address and size should be page aligned and the supported attributes can be > > +retrieved with KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES. > > + > > +The "flags" field may be used for future extensions and should be set to 0s. > > + > > 5. The kvm_run structure > > ======================== > > > > @@ -8270,6 +8323,16 @@ structure. > > When getting the Modified Change Topology Report value, the attr->addr > > must point to a byte where the value will be stored or retrieved from. > > > > +8.40 KVM_CAP_MEMORY_ATTRIBUTES > > +------------------------------ > > + > > +:Capability: KVM_CAP_MEMORY_ATTRIBUTES > > +:Architectures: x86 > > +:Type: vm > > + > > +This capability indicates KVM supports per-page memory attributes and ioctls > > +KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES/KVM_SET_MEMORY_ATTRIBUTES are available. > > + > > 9. Known KVM API problems > > ========================= > > > > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > > index fbeaa9ddef59..a8e379a3afee 100644 > > --- a/arch/x86/kvm/Kconfig > > +++ b/arch/x86/kvm/Kconfig > > @@ -49,6 +49,7 @@ config KVM > > select SRCU > > select INTERVAL_TREE > > select HAVE_KVM_PM_NOTIFIER if PM > > + select HAVE_KVM_MEMORY_ATTRIBUTES > > help > > Support hosting fully virtualized guest machines using hardware > > virtualization extensions. You will need a fairly recent > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 8f874a964313..a784e2b06625 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -800,6 +800,9 @@ struct kvm { > > > > #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER > > struct notifier_block pm_notifier; > > +#endif > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > + struct xarray mem_attr_array; > > #endif > > char stats_id[KVM_STATS_NAME_SIZE]; > > }; > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index 64dfe9c07c87..5d0941acb5bb 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -1182,6 +1182,7 @@ struct kvm_ppc_resize_hpt { > > #define KVM_CAP_S390_CPU_TOPOLOGY 222 > > #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223 > > #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224 > > +#define KVM_CAP_MEMORY_ATTRIBUTES 225 > > > > #ifdef KVM_CAP_IRQ_ROUTING > > > > @@ -2238,4 +2239,20 @@ struct kvm_s390_zpci_op { > > /* flags for kvm_s390_zpci_op->u.reg_aen.flags */ > > #define KVM_S390_ZPCIOP_REGAEN_HOST (1 << 0) > > > > +/* Available with KVM_CAP_MEMORY_ATTRIBUTES */ > > +#define KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES _IOR(KVMIO, 0xd2, __u64) > > +#define KVM_SET_MEMORY_ATTRIBUTES _IOWR(KVMIO, 0xd3, struct kvm_memory_attributes) > > + > > +struct kvm_memory_attributes { > > + __u64 address; > > + __u64 size; > > + __u64 attributes; > > + __u64 flags; > > +}; > > + > > +#define KVM_MEMORY_ATTRIBUTE_READ (1ULL << 0) > > +#define KVM_MEMORY_ATTRIBUTE_WRITE (1ULL << 1) > > +#define KVM_MEMORY_ATTRIBUTE_EXECUTE (1ULL << 2) > > +#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) > > nit: how about using the BIT() macro for these? Might be the _BITULL() in include/uapi/linux/const.h since it will be used by userspace also. > > > + > > #endif /* __LINUX_KVM_H */ > > diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig > > index 800f9470e36b..effdea5dd4f0 100644 > > --- a/virt/kvm/Kconfig > > +++ b/virt/kvm/Kconfig > > @@ -19,6 +19,9 @@ config HAVE_KVM_IRQ_ROUTING > > config HAVE_KVM_DIRTY_RING > > bool > > > > +config HAVE_KVM_MEMORY_ATTRIBUTES > > + bool > > + > > # Only strongly ordered architectures can select this, as it doesn't > > # put any explicit constraint on userspace ordering. They can also > > # select the _ACQ_REL version. > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 1782c4555d94..7f0f5e9f2406 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -1150,6 +1150,9 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname) > > spin_lock_init(&kvm->mn_invalidate_lock); > > rcuwait_init(&kvm->mn_memslots_update_rcuwait); > > xa_init(&kvm->vcpu_array); > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > + xa_init(&kvm->mem_attr_array); > > +#endif > > > > INIT_LIST_HEAD(&kvm->gpc_list); > > spin_lock_init(&kvm->gpc_lock); > > @@ -1323,6 +1326,9 @@ static void kvm_destroy_vm(struct kvm *kvm) > > kvm_free_memslots(kvm, &kvm->__memslots[i][0]); > > kvm_free_memslots(kvm, &kvm->__memslots[i][1]); > > } > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > + xa_destroy(&kvm->mem_attr_array); > > +#endif > > cleanup_srcu_struct(&kvm->irq_srcu); > > cleanup_srcu_struct(&kvm->srcu); > > kvm_arch_free_vm(kvm); > > @@ -2323,6 +2329,49 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm, > > } > > #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */ > > > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > +static u64 kvm_supported_mem_attributes(struct kvm *kvm) > > +{ > > + return 0; > > +} > > + > > +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, > > + struct kvm_memory_attributes *attrs) > > +{ > > + gfn_t start, end; > > + unsigned long i; > > + void *entry; > > + u64 supported_attrs = kvm_supported_mem_attributes(kvm); > > + > > + /* flags is currently not used. */ > > nit: "is reserved"? I think it makes it a bit clearer what its purpose is. OK, then: flags is reserved for future extention and currently is not used. > > > + if (attrs->flags) > > + return -EINVAL; > > + if (attrs->attributes & ~supported_attrs) > > + return -EINVAL; > > + if (attrs->size == 0 || attrs->address + attrs->size < attrs->address) > > + return -EINVAL; > > + if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size)) > > + return -EINVAL; > > + > > + start = attrs->address >> PAGE_SHIFT; > > + end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT; > > Would using existing helpers be better for getting the frame numbers? Yes, gpa_to_gfn() can be used. > Also, the code checks that the address and size are page aligned, so > the end rounding up seems redundant, and might even be wrong if the > address+size-1 is close to the gfn_t limit (which this code tries to > avoid in an earlier check). That's right. > > > + entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL; > > + > > + mutex_lock(&kvm->lock); > > + for (i = start; i < end; i++) > > + if (xa_err(xa_store(&kvm->mem_attr_array, i, entry, > > + GFP_KERNEL_ACCOUNT))) > > + break; > > + mutex_unlock(&kvm->lock); > > + > > + attrs->address = i << PAGE_SHIFT; > > + attrs->size = (end - i) << PAGE_SHIFT; > > nit: helpers for these too? Similarly, gfn_to_gpa() will be used. > > With the end calculation fixed, > > Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx> > After adding the necessary configs for arm64 (on qemu/arm64): > Tested-by: Fuad Tabba <tabba@xxxxxxxxxx> Thanks. Chao > > Cheers, > /fuad > > > + > > + return 0; > > +} > > +#endif /* CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES */ > > + > > struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn) > > { > > return __gfn_to_memslot(kvm_memslots(kvm), gfn); > > @@ -4459,6 +4508,9 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) > > #ifdef CONFIG_HAVE_KVM_MSI > > case KVM_CAP_SIGNAL_MSI: > > #endif > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > + case KVM_CAP_MEMORY_ATTRIBUTES: > > +#endif > > #ifdef CONFIG_HAVE_KVM_IRQFD > > case KVM_CAP_IRQFD: > > case KVM_CAP_IRQFD_RESAMPLE: > > @@ -4804,6 +4856,30 @@ static long kvm_vm_ioctl(struct file *filp, > > break; > > } > > #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */ > > +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES > > + case KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES: { > > + u64 attrs = kvm_supported_mem_attributes(kvm); > > + > > + r = -EFAULT; > > + if (copy_to_user(argp, &attrs, sizeof(attrs))) > > + goto out; > > + r = 0; > > + break; > > + } > > + case KVM_SET_MEMORY_ATTRIBUTES: { > > + struct kvm_memory_attributes attrs; > > + > > + r = -EFAULT; > > + if (copy_from_user(&attrs, argp, sizeof(attrs))) > > + goto out; > > + > > + r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs); > > + > > + if (!r && copy_to_user(argp, &attrs, sizeof(attrs))) > > + r = -EFAULT; > > + break; > > + } > > +#endif /* CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES */ > > case KVM_CREATE_DEVICE: { > > struct kvm_create_device cd; > > > > -- > > 2.25.1 > >
