[Qemu-devel] [PATCH v5 21/23] sev: add debug encrypt and decrypt commands

[Brijesh Singh <brijesh.singh@amd.com>]

KVM_SEV_DBG_DECRYPT and KVM_SEV_DBG_ENCRYPT commands are used for
decrypting and encrypting guest memory region. The command works only if
the guest policy allows the debugging.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 accel/kvm/kvm-all.c  |  1 +
 accel/kvm/sev.c      | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/sysemu/sev.h |  1 +
 3 files changed, 72 insertions(+)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index d35eebb97901..b069261de32a 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -1677,6 +1677,7 @@ static int kvm_init(MachineState *ms)
         }
 
         kvm_state->memcrypt_encrypt_data = sev_encrypt_data;
+        kvm_state->memcrypt_debug_ops = sev_set_debug_ops;
     }
 
     ret = kvm_arch_init(ms, s);
diff --git a/accel/kvm/sev.c b/accel/kvm/sev.c
index fbbd99becc0a..3edfb5b08416 100644
--- a/accel/kvm/sev.c
+++ b/accel/kvm/sev.c
@@ -22,6 +22,7 @@
 
 #define DEFAULT_GUEST_POLICY    0x1 /* disable debug */
 #define DEFAULT_SEV_DEVICE      "/dev/sev"
+#define GUEST_POLICY_DBG_BIT    0x1
 
 #define DEBUG_SEV
 #ifdef DEBUG_SEV
@@ -34,6 +35,7 @@
 
 static int sev_fd;
 static SEVState *sev_state;
+static MemoryRegionRAMReadWriteOps  sev_ops;
 
 #define SEV_FW_MAX_ERROR      0x17
 
@@ -483,6 +485,49 @@ sev_vm_state_change(void *opaque, int running, RunState state)
     }
 }
 
+static int
+sev_dbg_enc_dec(uint8_t *dst, const uint8_t *src, uint32_t len, bool write)
+{
+    int ret, error;
+    struct kvm_sev_dbg *dbg;
+    dbg = g_malloc0(sizeof(*dbg));
+    if (!dbg) {
+        return 1;
+    }
+
+    dbg->src_uaddr = (unsigned long)src;
+    dbg->dst_uaddr = (unsigned long)dst;
+    dbg->len = len;
+
+    ret = sev_ioctl(write ? KVM_SEV_DBG_ENCRYPT : KVM_SEV_DBG_DECRYPT,
+                    dbg, &error);
+    if (ret) {
+        error_report("%s (%s) %#llx->%#llx+%#x ret=%d fw_error=%d '%s'",
+                     __func__, write ? "write" : "read", dbg->src_uaddr,
+                     dbg->dst_uaddr, dbg->len, ret, error,
+                     fw_error_to_str(error));
+    }
+
+    g_free(dbg);
+    return ret;
+}
+
+static int
+sev_mem_read(uint8_t *dst, const uint8_t *src, uint32_t len, MemTxAttrs attrs)
+{
+    assert(attrs.debug);
+
+    return sev_dbg_enc_dec(dst, src, len, false);
+}
+
+static int
+sev_mem_write(uint8_t *dst, const uint8_t *src, uint32_t len, MemTxAttrs attrs)
+{
+    assert(attrs.debug);
+
+    return sev_dbg_enc_dec(dst, src, len, true);
+}
+
 void *
 sev_guest_init(const char *id)
 {
@@ -549,6 +594,31 @@ sev_encrypt_data(void *handle, uint8_t *ptr, uint64_t len)
     return 0;
 }
 
+void
+sev_set_debug_ops(void *handle, MemoryRegion *mr)
+{
+    int policy;
+    SEVState *s = (SEVState *)handle;
+
+    policy = object_property_get_int(OBJECT(s->sev_info),
+                                     "policy", &error_abort);
+
+    /*
+     * Check if guest policy supports debugging
+     * Bit 0 :
+     *   0 - debug allowed
+     *   1 - debug is not allowed
+     */
+    if (policy & GUEST_POLICY_DBG_BIT) {
+        return;
+    }
+
+    sev_ops.read = sev_mem_read;
+    sev_ops.write = sev_mem_write;
+
+    memory_region_set_ram_debug_ops(mr, &sev_ops);
+}
+
 static void
 sev_register_types(void)
 {
diff --git a/include/sysemu/sev.h b/include/sysemu/sev.h
index 3af945935b60..7c50d33af4a9 100644
--- a/include/sysemu/sev.h
+++ b/include/sysemu/sev.h
@@ -71,6 +71,7 @@ typedef struct SEVState SEVState;
 
 void *sev_guest_init(const char *id);
 int sev_encrypt_data(void *handle, uint8_t *ptr, uint64_t len);
+void sev_set_debug_ops(void *handle, MemoryRegion *mr);
 
 #endif
 
-- 
2.9.5