sev: Remove false abstraction of flash encryption

When AMD's SEV memory encryption is in use, flash memory banks (which are
initialed by pc_system_flash_map()) need to be encrypted with the guest's
key, so that the guest can read them.

That's abstracted via the kvm_memcrypt_encrypt_data() callback in the KVM
state.. except, that it doesn't really abstract much at all.

For starters, the only call site is in code specific to the 'pc'
family of machine types, so it's obviously specific to those and to
x86 to begin with.  But it makes a bunch of further assumptions that
need not be true about an arbitrary confidential guest system based on
memory encryption, let alone one based on other mechanisms:

 * it assumes that the flash memory is defined to be encrypted with the
   guest key, rather than being shared with hypervisor
 * it assumes that that hypervisor has some mechanism to encrypt data into
   the guest, even though it can't decrypt it out, since that's the whole
   point
 * the interface assumes that this encrypt can be done in place, which
   implies that the hypervisor can write into a confidential guests's
   memory, even if what it writes isn't meaningful

So really, this "abstraction" is actually pretty specific to the way SEV
works.  So, this patch removes it and instead has the PC flash
initialization code call into a SEV specific callback.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>

2 files changed, 4 insertions, 36 deletions

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 5164d83..3526e88 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -123,10 +123,6 @@ struct KVMState
     KVMMemoryListener memory_listener;
     QLIST_HEAD(, KVMParkedVcpu) kvm_parked_vcpus;
 
-    /* memory encryption */
-    void *memcrypt_handle;
-    int (*memcrypt_encrypt_data)(void *handle, uint8_t *ptr, uint64_t len);
-
     /* For "info mtree -f" to tell if an MR is registered in KVM */
     int nr_as;
     struct KVMAs {
@@ -225,26 +221,6 @@ int kvm_get_max_memslots(void)
     return s->nr_slots;
 }
 
-bool kvm_memcrypt_enabled(void)
-{
-    if (kvm_state && kvm_state->memcrypt_handle) {
-        return true;
-    }
-
-    return false;
-}
-
-int kvm_memcrypt_encrypt_data(uint8_t *ptr, uint64_t len)
-{
-    if (kvm_state->memcrypt_handle &&
-        kvm_state->memcrypt_encrypt_data) {
-        return kvm_state->memcrypt_encrypt_data(kvm_state->memcrypt_handle,
-                                              ptr, len);
-    }
-
-    return 1;
-}
-
 /* Called with KVMMemoryListener.slots_lock held */
 static KVMSlot *kvm_get_free_slot(KVMMemoryListener *kml)
 {
@@ -2209,13 +2185,10 @@ static int kvm_init(MachineState *ms)
      * encryption context.
      */
     if (ms->memory_encryption) {
-        kvm_state->memcrypt_handle = sev_guest_init(ms->memory_encryption);
-        if (!kvm_state->memcrypt_handle) {
-            ret = -1;
+        ret = sev_guest_init(ms->memory_encryption);
+        if (ret < 0) {
             goto err;
         }
-
-        kvm_state->memcrypt_encrypt_data = sev_encrypt_data;
     }
 
     ret = kvm_arch_init(ms, s);
diff --git a/accel/kvm/sev-stub.c b/accel/kvm/sev-stub.c
index 4f97452..5db9ab8 100644
--- a/accel/kvm/sev-stub.c
+++ b/accel/kvm/sev-stub.c
@@ -15,12 +15,7 @@
 #include "qemu-common.h"
 #include "sysemu/sev.h"
 
-int sev_encrypt_data(void *handle, uint8_t *ptr, uint64_t len)
+int sev_guest_init(const char *id)
 {
-    abort();
-}
-
-void *sev_guest_init(const char *id)
-{
-    return NULL;
+    return -1;
 }