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

[Michael Roth]

On Tue, Oct 12, 2021 at 07:20:41PM -0700, Krish Sadhukhan wrote:
> 
> 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
> 
> 
> 

Makes sense, I will use this naming convention for the next spin.