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    SubjectRe: [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions
    Hi Chao,

    On Wed, Jul 6, 2022 at 9:27 AM Chao Peng <chao.p.peng@linux.intel.com> 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 but differs that the
    > address in the region for private memory is gpa while SEV case it's hva.
    >
    > The private memory region is stored as xarray in KVM for memory
    > efficiency in normal usages and zapping existing memory mappings is also
    > a side effect of these two ioctls.
    >
    > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
    > ---
    > Documentation/virt/kvm/api.rst | 17 +++++++---
    > arch/x86/include/asm/kvm_host.h | 1 +
    > arch/x86/kvm/Kconfig | 1 +
    > arch/x86/kvm/mmu.h | 2 --
    > include/linux/kvm_host.h | 8 +++++
    > virt/kvm/kvm_main.c | 57 +++++++++++++++++++++++++++++++++
    > 6 files changed, 80 insertions(+), 6 deletions(-)
    >
    > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
    > index 5ecfc7fbe0ee..dfb4caecab73 100644
    > --- a/Documentation/virt/kvm/api.rst
    > +++ b/Documentation/virt/kvm/api.rst
    > @@ -4715,10 +4715,19 @@ Documentation/virt/kvm/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 dae190e19fce..92120e3a224e 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/Kconfig b/arch/x86/kvm/Kconfig
    > index 1f160801e2a7..05861b9656a4 100644
    > --- a/arch/x86/kvm/Kconfig
    > +++ b/arch/x86/kvm/Kconfig
    > @@ -50,6 +50,7 @@ config KVM
    > select HAVE_KVM_PM_NOTIFIER if PM
    > select HAVE_KVM_PRIVATE_MEM if X86_64
    > select MEMFILE_NOTIFIER if HAVE_KVM_PRIVATE_MEM
    > + select XARRAY_MULTI if HAVE_KVM_PRIVATE_MEM
    > help
    > Support hosting fully virtualized guest machines using hardware
    > virtualization extensions. You will need a fairly recent
    > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
    > index a99acec925eb..428cd2e88cbd 100644
    > --- a/arch/x86/kvm/mmu.h
    > +++ b/arch/x86/kvm/mmu.h
    > @@ -209,8 +209,6 @@ 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 1b203c8aa696..da33f8828456 100644
    > --- a/include/linux/kvm_host.h
    > +++ b/include/linux/kvm_host.h
    > @@ -260,6 +260,10 @@ 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);
    > +#endif
    > +
    > enum {
    > OUTSIDE_GUEST_MODE,
    > IN_GUEST_MODE,
    > @@ -795,6 +799,9 @@ 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, ...) \
    > @@ -1459,6 +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_private_mem_supported(struct kvm *kvm);
    >
    > #ifndef __KVM_HAVE_ARCH_VM_ALLOC
    > /*
    > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > index 230c8ff9659c..bb714c2a4b06 100644
    > --- a/virt/kvm/kvm_main.c
    > +++ b/virt/kvm/kvm_main.c
    > @@ -914,6 +914,35 @@ 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_PRIVATE 0x0001
    > +static int kvm_vm_ioctl_set_encrypted_region(struct kvm *kvm, unsigned int ioctl,
    > + struct kvm_enc_region *region)
    > +{
    > + unsigned long start, end;
    > + void *entry;
    > + int r;
    > +
    > + if (region->size == 0 || region->addr + region->size < region->addr)
    > + return -EINVAL;
    > + if (region->addr & (PAGE_SIZE - 1) || region->size & (PAGE_SIZE - 1))
    > + return -EINVAL;
    > +
    > + start = region->addr >> PAGE_SHIFT;
    > + end = (region->addr + region->size - 1) >> PAGE_SHIFT;
    > +
    > + entry = ioctl == KVM_MEMORY_ENCRYPT_REG_REGION ?
    > + xa_mk_value(KVM_MEM_ATTR_PRIVATE) : NULL;
    > +
    > + r = xa_err(xa_store_range(&kvm->mem_attr_array, start, end,
    > + entry, GFP_KERNEL_ACCOUNT));
    > +
    > + kvm_zap_gfn_range(kvm, start, end + 1);
    > +
    > + 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,
    > @@ -1138,6 +1167,9 @@ static struct kvm *kvm_create_vm(unsigned long type)
    > 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);
    > @@ -1305,6 +1337,9 @@ 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);
    > @@ -1508,6 +1543,11 @@ static void kvm_replace_memslot(struct kvm *kvm,
    > }
    > }
    >
    > +bool __weak kvm_arch_private_mem_supported(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;
    > @@ -4689,6 +4729,22 @@ 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;
    > +
    > + if (!kvm_arch_private_mem_supported(kvm))
    > + goto arch_vm_ioctl;
    > +
    > + r = -EFAULT;
    > + if (copy_from_user(&region, argp, sizeof(region)))
    > + goto out;
    > +
    > + r = kvm_vm_ioctl_set_encrypted_region(kvm, ioctl, &region);
    > + break;
    > + }
    > +#endif
    > case KVM_GET_DIRTY_LOG: {
    > struct kvm_dirty_log log;
    >
    > @@ -4842,6 +4898,7 @@ static long kvm_vm_ioctl(struct file *filp,
    > r = kvm_vm_ioctl_get_stats_fd(kvm);
    > break;
    > default:
    > +arch_vm_ioctl:

    It might be good to make this label conditional on
    CONFIG_HAVE_KVM_PRIVATE_MEM, otherwise you get a warning if
    CONFIG_HAVE_KVM_PRIVATE_MEM isn't defined.

    +#ifdef CONFIG_HAVE_KVM_PRIVATE_MEM
    arch_vm_ioctl:
    +#endif

    Cheers,
    /fuad





    > r = kvm_arch_vm_ioctl(filp, ioctl, arg);
    > }
    > out:
    > --
    > 2.25.1
    >

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