1 files changed, 66 insertions, 13 deletions

diff --git a/target/i386/sev.c b/target/i386/sev.c
index eede07f11d..025ff7a6f8 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -37,6 +37,7 @@
 #include "qapi/qmp/qerror.h"
 #include "exec/confidential-guest-support.h"
 #include "hw/i386/pc.h"
+#include "exec/address-spaces.h"
 
 #define TYPE_SEV_GUEST "sev-guest"
 OBJECT_DECLARE_SIMPLE_TYPE(SevGuestState, SEV_GUEST)
@@ -62,6 +63,7 @@ struct SevGuestState {
     char *session_file;
     uint32_t cbitpos;
     uint32_t reduced_phys_bits;
+    bool kernel_hashes;
 
     /* runtime state */
     uint32_t handle;
@@ -109,9 +111,19 @@ typedef struct QEMU_PACKED SevHashTable {
     SevHashTableEntry cmdline;
     SevHashTableEntry initrd;
     SevHashTableEntry kernel;
-    uint8_t padding[];
 } SevHashTable;
 
+/*
+ * Data encrypted by sev_encrypt_flash() must be padded to a multiple of
+ * 16 bytes.
+ */
+typedef struct QEMU_PACKED PaddedSevHashTable {
+    SevHashTable ht;
+    uint8_t padding[ROUND_UP(sizeof(SevHashTable), 16) - sizeof(SevHashTable)];
+} PaddedSevHashTable;
+
+QEMU_BUILD_BUG_ON(sizeof(PaddedSevHashTable) % 16 != 0);
+
 static SevGuestState *sev_guest;
 static Error *sev_mig_blocker;
 
@@ -327,6 +339,20 @@ sev_guest_set_sev_device(Object *obj, const char *value, Error **errp)
     sev->sev_device = g_strdup(value);
 }
 
+static bool sev_guest_get_kernel_hashes(Object *obj, Error **errp)
+{
+    SevGuestState *sev = SEV_GUEST(obj);
+
+    return sev->kernel_hashes;
+}
+
+static void sev_guest_set_kernel_hashes(Object *obj, bool value, Error **errp)
+{
+    SevGuestState *sev = SEV_GUEST(obj);
+
+    sev->kernel_hashes = value;
+}
+
 static void
 sev_guest_class_init(ObjectClass *oc, void *data)
 {
@@ -345,6 +371,11 @@ sev_guest_class_init(ObjectClass *oc, void *data)
                                   sev_guest_set_session_file);
     object_class_property_set_description(oc, "session-file",
             "guest owners session parameters (encoded with base64)");
+    object_class_property_add_bool(oc, "kernel-hashes",
+                                   sev_guest_get_kernel_hashes,
+                                   sev_guest_set_kernel_hashes);
+    object_class_property_set_description(oc, "kernel-hashes",
+            "add kernel hashes to guest firmware for measured Linux boot");
 }
 
 static void
@@ -1196,18 +1227,35 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
     uint8_t *data;
     SevHashTableDescriptor *area;
     SevHashTable *ht;
+    PaddedSevHashTable *padded_ht;
     uint8_t cmdline_hash[HASH_SIZE];
     uint8_t initrd_hash[HASH_SIZE];
     uint8_t kernel_hash[HASH_SIZE];
     uint8_t *hashp;
     size_t hash_len = HASH_SIZE;
-    int aligned_len;
+    hwaddr mapped_len = sizeof(*padded_ht);
+    MemTxAttrs attrs = { 0 };
+    bool ret = true;
+
+    /*
+     * Only add the kernel hashes if the sev-guest configuration explicitly
+     * stated kernel-hashes=on.
+     */
+    if (!sev_guest->kernel_hashes) {
+        return false;
+    }
 
     if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
-        error_setg(errp, "SEV: kernel specified but OVMF has no hash table guid");
+        error_setg(errp, "SEV: kernel specified but guest firmware "
+                         "has no hashes table GUID");
         return false;
     }
     area = (SevHashTableDescriptor *)data;
+    if (!area->base || area->size < sizeof(PaddedSevHashTable)) {
+        error_setg(errp, "SEV: guest firmware hashes table area is invalid "
+                         "(base=0x%x size=0x%x)", area->base, area->size);
+        return false;
+    }
 
     /*
      * Calculate hash of kernel command-line with the terminating null byte. If
@@ -1248,7 +1296,13 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
      * Populate the hashes table in the guest's memory at the OVMF-designated
      * area for the SEV hashes table
      */
-    ht = qemu_map_ram_ptr(NULL, area->base);
+    padded_ht = address_space_map(&address_space_memory, area->base,
+                                  &mapped_len, true, attrs);
+    if (!padded_ht || mapped_len != sizeof(*padded_ht)) {
+        error_setg(errp, "SEV: cannot map hashes table guest memory area");
+        return false;
+    }
+    ht = &padded_ht->ht;
 
     ht->guid = sev_hash_table_header_guid;
     ht->len = sizeof(*ht);
@@ -1265,18 +1319,17 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
     ht->kernel.len = sizeof(ht->kernel);
     memcpy(ht->kernel.hash, kernel_hash, sizeof(ht->kernel.hash));
 
-    /* When calling sev_encrypt_flash, the length has to be 16 byte aligned */
-    aligned_len = ROUND_UP(ht->len, 16);
-    if (aligned_len != ht->len) {
-        /* zero the excess data so the measurement can be reliably calculated */
-        memset(ht->padding, 0, aligned_len - ht->len);
-    }
+    /* zero the excess data so the measurement can be reliably calculated */
+    memset(padded_ht->padding, 0, sizeof(padded_ht->padding));
 
-    if (sev_encrypt_flash((uint8_t *)ht, aligned_len, errp) < 0) {
-        return false;
+    if (sev_encrypt_flash((uint8_t *)padded_ht, sizeof(*padded_ht), errp) < 0) {
+        ret = false;
     }
 
-    return true;
+    address_space_unmap(&address_space_memory, padded_ht,
+                        mapped_len, true, mapped_len);
+
+    return ret;
 }
 
 static void