[V4 3/8] KVM: selftests: add hooks for managing encrypted guest memory

From: Peter Gonda
Date: Mon Aug 29 2022 - 13:11:14 EST

From: Michael Roth <michael.roth@xxxxxxx>

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.

Reviewed-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
---
.../selftests/kvm/include/kvm_util_base.h | 17 ++++++
tools/testing/selftests/kvm/lib/kvm_util.c | 52 +++++++++++++++++--
2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 59d52b58a1a6..5ecde5ad4c2f 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -33,6 +33,7 @@ typedef uint64_t vm_vaddr_t; /* Virtual Machine (Guest) virtual address */
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;
@@ -65,6 +66,14 @@ 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;
@@ -89,6 +98,7 @@ struct kvm_vm {
vm_vaddr_t idt;
vm_vaddr_t handlers;
uint32_t dirty_ring_size;
+ struct vm_memcrypt memcrypt;

/* Cache of information for binary stats interface */
int stats_fd;
@@ -849,4 +859,11 @@ static inline int __vm_disable_nx_huge_pages(struct kvm_vm *vm)
return __vm_enable_cap(vm, KVM_CAP_VM_DISABLE_NX_HUGE_PAGES, 0);
}

+void vm_set_memory_encryption(struct kvm_vm *vm, bool enc_by_default, bool has_enc_bit,
+ uint8_t enc_bit);
+
+const struct sparsebit *vm_get_encrypted_phy_pages(struct kvm_vm *vm, int slot,
+ vm_paddr_t *gpa_start,
+ uint64_t *size);
+
#endif /* SELFTEST_KVM_UTIL_BASE_H */
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 06559994711e..53b9a509c1d5 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -553,6 +553,7 @@ static void __vm_mem_region_delete(struct kvm_vm *vm,
vm_ioctl(vm, KVM_SET_USER_MEMORY_REGION, &region->region);

sparsebit_free(&region->unused_phy_pages);
+ sparsebit_free(&region->encrypted_phy_pages);
ret = munmap(region->mmap_start, region->mmap_size);
TEST_ASSERT(!ret, __KVM_SYSCALL_ERROR("munmap()", ret));

@@ -893,6 +894,7 @@ 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;
@@ -1108,6 +1110,7 @@ struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
* 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
*
@@ -1119,8 +1122,9 @@ struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
* 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;
@@ -1152,12 +1156,22 @@ 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);
+ }

return base * vm->page_size;
}

+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, num, paddr_min, memslot,
+ vm->memcrypt.enc_by_default);
+}
+
vm_paddr_t vm_phy_page_alloc(struct kvm_vm *vm, vm_paddr_t paddr_min,
uint32_t memslot)
{
@@ -1741,6 +1755,10 @@ 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);
@@ -1989,3 +2007,31 @@ void __vm_get_stat(struct kvm_vm *vm, const char *stat_name, uint64_t *data,
break;
}
}
+
+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;
+}
+
+const 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;
+
+ if (!vm->memcrypt.enabled)
+ return NULL;
+
+ region = memslot2region(vm, slot);
+ if (!region)
+ return NULL;
+
+ *size = region->region.memory_size;
+ *gpa_start = region->region.guest_phys_addr;
+
+ return region->encrypted_phy_pages;
+}
--
2.37.2.672.g94769d06f0-goog