Hi, On Thu, Sep 15, 2022 at 3:38 PM Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > If CONFIG_HAVE_KVM_PRIVATE_MEM=y, userspace can register/unregister the > guest private memory regions through KVM_MEMORY_ENCRYPT_{UN,}REG_REGION > ioctls. The patch reuses existing SEV ioctl number but differs that the > address in the region for KVM_PRIVATE_MEM case is gpa while for SEV case > it's hva. Which usages should the ioctls go is determined by the newly > added kvm_arch_has_private_mem(). Architecture which supports > KVM_PRIVATE_MEM should override this function. > > The current implementation defaults all memory to private. The shared > memory regions are stored in a xarray variable for memory efficiency and > zapping existing memory mappings is also a side effect of these two > ioctls when defined. > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 17 ++++++-- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/mmu.h | 2 - > include/linux/kvm_host.h | 13 ++++++ > virt/kvm/kvm_main.c | 73 +++++++++++++++++++++++++++++++++ > 5 files changed, 100 insertions(+), 6 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 1a6c003b2a0b..c0f800d04ffc 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -4715,10 +4715,19 @@ Documentation/virt/kvm/x86/amd-memory-encryption.rst. > This ioctl can be used to register a guest memory region which may > contain encrypted data (e.g. guest RAM, SMRAM etc). > > -It is used in the SEV-enabled guest. When encryption is enabled, a guest > -memory region may contain encrypted data. The SEV memory encryption > -engine uses a tweak such that two identical plaintext pages, each at > -different locations will have differing ciphertexts. So swapping or > +Currently this ioctl supports registering memory regions for two usages: > +private memory and SEV-encrypted memory. > + > +When private memory is enabled, this ioctl is used to register guest private > +memory region and the addr/size of kvm_enc_region represents guest physical > +address (GPA). In this usage, this ioctl zaps the existing guest memory > +mappings in KVM that fallen into the region. > + > +When SEV-encrypted memory is enabled, this ioctl is used to register guest > +memory region which may contain encrypted data for a SEV-enabled guest. The > +addr/size of kvm_enc_region represents userspace address (HVA). The SEV > +memory encryption engine uses a tweak such that two identical plaintext pages, > +each at different locations will have differing ciphertexts. So swapping or > moving ciphertext of those pages will not result in plaintext being > swapped. So relocating (or migrating) physical backing pages for the SEV > guest will require some additional steps. > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 2c96c43c313a..cfad6ba1a70a 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -37,6 +37,7 @@ > #include <asm/hyperv-tlfs.h> > > #define __KVM_HAVE_ARCH_VCPU_DEBUGFS > +#define __KVM_HAVE_ZAP_GFN_RANGE > > #define KVM_MAX_VCPUS 1024 > > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h > index 6bdaacb6faa0..c94b620bf94b 100644 > --- a/arch/x86/kvm/mmu.h > +++ b/arch/x86/kvm/mmu.h > @@ -211,8 +211,6 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, > return -(u32)fault & errcode; > } > > -void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end); > - > int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu); > > int kvm_mmu_post_init_vm(struct kvm *kvm); > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 2125b50f6345..d65690cae80b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -260,6 +260,15 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range); > bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range); > #endif > > +#ifdef __KVM_HAVE_ZAP_GFN_RANGE > +void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end); > +#else > +static inline void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start > + gfn_t gfn_end) > +{ > +} > +#endif > + > enum { > OUTSIDE_GUEST_MODE, > IN_GUEST_MODE, > @@ -795,6 +804,9 @@ struct kvm { > struct notifier_block pm_notifier; > #endif > char stats_id[KVM_STATS_NAME_SIZE]; > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > + struct xarray mem_attr_array; > +#endif > }; > > #define kvm_err(fmt, ...) \ > @@ -1454,6 +1466,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu); > int kvm_arch_post_init_vm(struct kvm *kvm); > void kvm_arch_pre_destroy_vm(struct kvm *kvm); > int kvm_arch_create_vm_debugfs(struct kvm *kvm); > +bool kvm_arch_has_private_mem(struct kvm *kvm); > > #ifndef __KVM_HAVE_ARCH_VM_ALLOC > /* > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index fa9dd2d2c001..de5cce8c82c7 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -937,6 +937,47 @@ static int kvm_init_mmu_notifier(struct kvm *kvm) > > #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */ > > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > +#define KVM_MEM_ATTR_SHARED 0x0001 > +static int kvm_vm_ioctl_set_mem_attr(struct kvm *kvm, gpa_t gpa, gpa_t size, > + bool is_private) > +{ I wonder if this ioctl should be implemented as an arch-specific ioctl. In this patch it performs some actions that pKVM might not need or might want to do differently. pKVM tracks the sharing status in the stage-2 page table's software bits, so it can avoid the overhead of using mem_attr_array. Also, this ioctl calls kvm_zap_gfn_range(), as does the invalidation notifier (introduced in patch 8). For pKVM, the kind of zapping (or the information conveyed to the hypervisor) might need to be different depending on the cause; whether it's invalidation or change of sharing status. Thanks, /fuad > + gfn_t start, end; > + unsigned long index; > + void *entry; > + int r; > + > + if (size == 0 || gpa + size < gpa) > + return -EINVAL; > + if (gpa & (PAGE_SIZE - 1) || size & (PAGE_SIZE - 1)) > + return -EINVAL; > + > + start = gpa >> PAGE_SHIFT; > + end = (gpa + size - 1 + PAGE_SIZE) >> PAGE_SHIFT; > + > + /* > + * Guest memory defaults to private, kvm->mem_attr_array only stores > + * shared memory. > + */ > + entry = is_private ? NULL : xa_mk_value(KVM_MEM_ATTR_SHARED); > + > + for (index = start; index < end; index++) { > + r = xa_err(xa_store(&kvm->mem_attr_array, index, entry, > + GFP_KERNEL_ACCOUNT)); > + if (r) > + goto err; > + } > + > + kvm_zap_gfn_range(kvm, start, end); > + > + return r; > +err: > + for (; index > start; index--) > + xa_erase(&kvm->mem_attr_array, index); > + return r; > +} > +#endif /* CONFIG_HAVE_KVM_PRIVATE_MEM */ > + > #ifdef CONFIG_HAVE_KVM_PM_NOTIFIER > static int kvm_pm_notifier_call(struct notifier_block *bl, > unsigned long state, > @@ -1165,6 +1206,9 @@ 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_PRIVATE_MEM > + xa_init(&kvm->mem_attr_array); > +#endif > > INIT_LIST_HEAD(&kvm->gpc_list); > spin_lock_init(&kvm->gpc_lock); > @@ -1338,6 +1382,9 @@ 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_PRIVATE_MEM > + xa_destroy(&kvm->mem_attr_array); > +#endif > cleanup_srcu_struct(&kvm->irq_srcu); > cleanup_srcu_struct(&kvm->srcu); > kvm_arch_free_vm(kvm); > @@ -1541,6 +1588,11 @@ static void kvm_replace_memslot(struct kvm *kvm, > } > } > > +bool __weak kvm_arch_has_private_mem(struct kvm *kvm) > +{ > + return false; > +} > + > static int check_memory_region_flags(const struct kvm_user_mem_region *mem) > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > @@ -4703,6 +4755,24 @@ static long kvm_vm_ioctl(struct file *filp, > r = kvm_vm_ioctl_set_memory_region(kvm, &mem); > break; > } > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > + case KVM_MEMORY_ENCRYPT_REG_REGION: > + case KVM_MEMORY_ENCRYPT_UNREG_REGION: { > + struct kvm_enc_region region; > + bool set = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION; > + > + if (!kvm_arch_has_private_mem(kvm)) > + goto arch_vm_ioctl; > + > + r = -EFAULT; > + if (copy_from_user(®ion, argp, sizeof(region))) > + goto out; > + > + r = kvm_vm_ioctl_set_mem_attr(kvm, region.addr, > + region.size, set); > + break; > + } > +#endif > case KVM_GET_DIRTY_LOG: { > struct kvm_dirty_log log; > > @@ -4856,6 +4926,9 @@ static long kvm_vm_ioctl(struct file *filp, > r = kvm_vm_ioctl_get_stats_fd(kvm); > break; > default: > +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM > +arch_vm_ioctl: > +#endif > r = kvm_arch_vm_ioctl(filp, ioctl, arg); > } > out: > -- > 2.25.1 >