Re: [RFC 02/16] KVM: selftests: add hooks for managing encrypted guest memory

[Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>]

On 10/5/21 4:44 PM, Michael Roth wrote:
> VM implementations that make use of encrypted memory need a way to
> configure things like the encryption/shared bit position for page
> table handling, the default encryption policy for internal allocations
> made by the core library, and a way to fetch the list/bitmap of
> encrypted pages to do the actual memory encryption. Add an interface to
> configure these parameters. Also introduce a sparsebit map to track
> allocations/mappings that should be treated as encrypted, and provide
> a way for VM implementations to retrieve it to handle operations
> related memory encryption.
>
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
>   .../testing/selftests/kvm/include/kvm_util.h  |  6 ++
>   tools/testing/selftests/kvm/lib/kvm_util.c    | 63 +++++++++++++++++--
>   .../selftests/kvm/lib/kvm_util_internal.h     | 10 +++
>   3 files changed, 75 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 010b59b13917..f417de80596c 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -348,6 +348,12 @@ int vm_create_device(struct kvm_vm *vm, struct kvm_create_device *cd);
>   
>   void assert_on_unhandled_exception(struct kvm_vm *vm, uint32_t vcpuid);
>   
> +void vm_set_memory_encryption(struct kvm_vm *vm, bool enc_by_default, bool has_enc_bit,
> +			      uint8_t enc_bit);
> +struct sparsebit *vm_get_encrypted_phy_pages(struct kvm_vm *vm, int slot,
> +					     vm_paddr_t *gpa_start,
> +					     uint64_t *size);
> +
>   /* Common ucalls */
>   enum {
>   	UCALL_NONE,
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 92f59adddebe..c58f930dedd2 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -631,6 +631,7 @@ static void __vm_mem_region_delete(struct kvm_vm *vm,
>   		    "rc: %i errno: %i", ret, errno);
>   
>   	sparsebit_free(&region->unused_phy_pages);
> +	sparsebit_free(&region->encrypted_phy_pages);
>   	ret = munmap(region->mmap_start, region->mmap_size);
>   	TEST_ASSERT(ret == 0, "munmap failed, rc: %i errno: %i", ret, errno);
>   
> @@ -924,6 +925,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
>   	}
>   
>   	region->unused_phy_pages = sparsebit_alloc();
> +	region->encrypted_phy_pages = sparsebit_alloc();
>   	sparsebit_set_num(region->unused_phy_pages,
>   		guest_paddr >> vm->page_shift, npages);
>   	region->region.slot = slot;
> @@ -1153,6 +1155,7 @@ void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid)
>    *   num - number of pages
>    *   paddr_min - Physical address minimum
>    *   memslot - Memory region to allocate page from
> + *   encrypt - Whether to treat the pages as encrypted
>    *
>    * Output Args: None
>    *
> @@ -1164,11 +1167,13 @@ void vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpuid)
>    * and their base address is returned. A TEST_ASSERT failure occurs if
>    * not enough pages are available at or above paddr_min.
>    */
> -vm_paddr_t vm_phy_pages_alloc(struct kvm_vm *vm, size_t num,
> -			      vm_paddr_t paddr_min, uint32_t memslot)
> +static vm_paddr_t
> +_vm_phy_pages_alloc(struct kvm_vm *vm, size_t num, vm_paddr_t paddr_min,
> +		    uint32_t memslot, bool encrypt)
>   {
>   	struct userspace_mem_region *region;
>   	sparsebit_idx_t pg, base;
> +	vm_paddr_t gpa;
>   
>   	TEST_ASSERT(num > 0, "Must allocate at least one page");
>   
> @@ -1198,10 +1203,25 @@ vm_paddr_t vm_phy_pages_alloc(struct kvm_vm *vm, size_t num,
>   		abort();
>   	}
>   
> -	for (pg = base; pg < base + num; ++pg)
> +	for (pg = base; pg < base + num; ++pg) {
>   		sparsebit_clear(region->unused_phy_pages, pg);
> +		if (encrypt)
> +			sparsebit_set(region->encrypted_phy_pages, pg);
> +	}
> +
> +	gpa = base * vm->page_size;
>   
> -	return base * vm->page_size;
> +	if (encrypt && vm->memcrypt.has_enc_bit)
> +		gpa |= (1ULL << vm->memcrypt.enc_bit);
> +
> +	return gpa;
> +}
> +
> +vm_paddr_t vm_phy_pages_alloc(struct kvm_vm *vm, size_t num,
> +			      vm_paddr_t paddr_min, uint32_t memslot)
> +{
> +	return _vm_phy_pages_alloc(vm, 1, paddr_min, memslot,
> +				   vm->memcrypt.enc_by_default);
>   }
>   
>   vm_paddr_t vm_phy_page_alloc(struct kvm_vm *vm, vm_paddr_t paddr_min,
> @@ -2146,6 +2166,10 @@ void vm_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent)
>   			region->host_mem);
>   		fprintf(stream, "%*sunused_phy_pages: ", indent + 2, "");
>   		sparsebit_dump(stream, region->unused_phy_pages, 0);
> +		if (vm->memcrypt.enabled) {
> +			fprintf(stream, "%*sencrypted_phy_pages: ", indent + 2, "");
> +			sparsebit_dump(stream, region->encrypted_phy_pages, 0);
> +		}
>   	}
>   	fprintf(stream, "%*sMapped Virtual Pages:\n", indent, "");
>   	sparsebit_dump(stream, vm->vpages_mapped, indent + 2);
> @@ -2343,3 +2367,34 @@ int vcpu_get_stats_fd(struct kvm_vm *vm, uint32_t vcpuid)
>   
>   	return ioctl(vcpu->fd, KVM_GET_STATS_FD, NULL);
>   }
> +
> +void vm_set_memory_encryption(struct kvm_vm *vm, bool enc_by_default, bool has_enc_bit,
> +			      uint8_t enc_bit)
> +{
> +	vm->memcrypt.enabled = true;
> +	vm->memcrypt.enc_by_default = enc_by_default;
> +	vm->memcrypt.has_enc_bit = has_enc_bit;
> +	vm->memcrypt.enc_bit = enc_bit;
> +}
> +
> +struct sparsebit *
> +vm_get_encrypted_phy_pages(struct kvm_vm *vm, int slot, vm_paddr_t *gpa_start,
> +			   uint64_t *size)
> +{
> +	struct userspace_mem_region *region;
> +	struct sparsebit *encrypted_phy_pages;
> +
> +	if (!vm->memcrypt.enabled)
> +		return NULL;
> +
> +	region = memslot2region(vm, slot);
> +	if (!region)
> +		return NULL;
> +
> +	encrypted_phy_pages = sparsebit_alloc();
> +	sparsebit_copy(encrypted_phy_pages, region->encrypted_phy_pages);
> +	*size = region->region.memory_size;
> +	*gpa_start = region->region.guest_phys_addr;
> +
> +	return encrypted_phy_pages;
> +}
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util_internal.h b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> index a03febc24ba6..99ccab86115c 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> +++ b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> @@ -16,6 +16,7 @@
>   struct userspace_mem_region {
>   	struct kvm_userspace_memory_region region;
>   	struct sparsebit *unused_phy_pages;
> +	struct sparsebit *encrypted_phy_pages;
>   	int fd;
>   	off_t offset;
>   	void *host_mem;
> @@ -44,6 +45,14 @@ struct userspace_mem_regions {
>   	DECLARE_HASHTABLE(slot_hash, 9);
>   };
>   
> +/* Memory encryption policy/configuration. */
> +struct vm_memcrypt {
> +	bool enabled;
> +	int8_t enc_by_default;
> +	bool has_enc_bit;
> +	int8_t enc_bit;
> +};
> +
>   struct kvm_vm {
>   	int mode;
>   	unsigned long type;
> @@ -67,6 +76,7 @@ struct kvm_vm {
>   	vm_vaddr_t idt;
>   	vm_vaddr_t handlers;
>   	uint32_t dirty_ring_size;
> +	struct vm_memcrypt memcrypt;


For readability, it's probably better to adopt a standard naming 
convention for structures, members and  functions ?  For example,

        encrypted_phy_pages    ->     enc_phy_pages

        struct vm_memcrypt  {    ->    struct vm_mem_enc {

        struct vm_memcrypt memcrypt    ->    struct vm_mem_enc  mem_enc

        vm_get_encrypted_phy_pages()    -> vm_get_enc_phy_pages



>   };
>   
>   struct vcpu *vcpu_find(struct kvm_vm *vm, uint32_t vcpuid);