i386/sev: Extract build_kernel_loader_hashes

Extract the building of the kernel hashes table out from
sev_add_kernel_loader_hashes() to allow building it in
other memory areas (for SNP support).

No functional change intended.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-22-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/sev.c

@@ -1754,45 +1754,16 @@ static const QemuUUID sev_cmdline_entry_guid = {
                     0x4d, 0x36, 0xab, 0x2a)
 };
 
-/*
+static bool build_kernel_loader_hashes(PaddedSevHashTable *padded_ht,
- * Add the hashes of the linux kernel/initrd/cmdline to an encrypted guest page
+                                       SevKernelLoaderContext *ctx,
- * which is included in SEV's initial memory measurement.
+                                       Error **errp)
- */
-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;
-    hwaddr mapped_len = sizeof(*padded_ht);
-    MemTxAttrs attrs = { 0 };
-    bool ret = true;
-    SevCommonState *sev_common = SEV_COMMON(MACHINE(qdev_get_machine())->cgs);
-
-    /*
-     * Only add the kernel hashes if the sev-guest configuration explicitly
-     * stated kernel-hashes=on.
-     */
-    if (!sev_common->kernel_hashes) {
-        return false;
-    }
-
-    if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
-        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
@@ -1829,16 +1800,6 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
     }
     assert(hash_len == HASH_SIZE);
 
-    /*
-     * Populate the hashes table in the guest's memory at the OVMF-designated
-     * area for the SEV hashes table
-     */
-    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;
@@ -1859,10 +1820,63 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
     /* zero the excess data so the measurement can be reliably calculated */
     memset(padded_ht->padding, 0, sizeof(padded_ht->padding));
 
+    return true;
+}
+
+/*
+ * Add the hashes of the linux kernel/initrd/cmdline to an encrypted guest page
+ * which is included in SEV's initial memory measurement.
+ */
+bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp)
+{
+    uint8_t *data;
+    SevHashTableDescriptor *area;
+    PaddedSevHashTable *padded_ht;
+    hwaddr mapped_len = sizeof(*padded_ht);
+    MemTxAttrs attrs = { 0 };
+    bool ret = true;
+    SevCommonState *sev_common = SEV_COMMON(MACHINE(qdev_get_machine())->cgs);
+
+    /*
+     * Only add the kernel hashes if the sev-guest configuration explicitly
+     * stated kernel-hashes=on.
+     */
+    if (!sev_common->kernel_hashes) {
+        return false;
+    }
+
+    if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
+        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;
+    }
+
+    /*
+     * Populate the hashes table in the guest's memory at the OVMF-designated
+     * area for the SEV hashes table
+     */
+    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;
+    }
+
+    if (build_kernel_loader_hashes(padded_ht, ctx, errp)) {
         if (sev_encrypt_flash(area->base, (uint8_t *)padded_ht,
                               sizeof(*padded_ht), errp) < 0) {
             ret = false;
         }
+    } else {
+        ret = false;
+    }
 
     address_space_unmap(&address_space_memory, padded_ht,
                         mapped_len, true, mapped_len);