[Qemu-devel] [PATCH v3 5/5] migration: Add capabilities validation

[Yury Kotov <yury-kotov@yandex-team.ru>]

Currently we don't check which capabilities set in the source QEMU.
We just expect that the target QEMU has the same enabled capabilities.

Add explicit validation for capabilities to make sure that the target VM
has them too. This is enabled for only new capabilities to keep compatibily.

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
---
 migration/savevm.c | 137 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)

diff --git a/migration/savevm.c b/migration/savevm.c
index 322660438d..a721cf5868 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -57,6 +57,7 @@
 #include "sysemu/replay.h"
 #include "qjson.h"
 #include "migration/colo.h"
+#include "qemu/bitmap.h"
 
 #ifndef ETH_P_RARP
 #define ETH_P_RARP 0x8035
@@ -316,6 +317,8 @@ typedef struct SaveState {
     uint32_t len;
     const char *name;
     uint32_t target_page_bits;
+    uint32_t caps_count;
+    MigrationCapability *capabilities;
 } SaveState;
 
 static SaveState savevm_state = {
@@ -323,15 +326,51 @@ static SaveState savevm_state = {
     .global_section_id = 0,
 };
 
+static bool should_validate_capability(int capability)
+{
+    assert(capability >= 0 && capability < MIGRATION_CAPABILITY__MAX);
+    /* Validate only new capabilities to keep compatibility. */
+    switch (capability) {
+    case MIGRATION_CAPABILITY_X_IGNORE_SHARED:
+        return true;
+    default:
+        return false;
+    }
+}
+
+static uint32_t get_validatable_capabilities_count(void)
+{
+    MigrationState *s = migrate_get_current();
+    uint32_t result = 0;
+    int i;
+    for (i = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
+        if (should_validate_capability(i) && s->enabled_capabilities[i]) {
+            result++;
+        }
+    }
+    return result;
+}
+
 static int configuration_pre_save(void *opaque)
 {
     SaveState *state = opaque;
     const char *current_name = MACHINE_GET_CLASS(current_machine)->name;
+    MigrationState *s = migrate_get_current();
+    int i, j;
 
     state->len = strlen(current_name);
     state->name = current_name;
     state->target_page_bits = qemu_target_page_bits();
 
+    state->caps_count = get_validatable_capabilities_count();
+    state->capabilities = g_renew(MigrationCapability, state->capabilities,
+                                  state->caps_count);
+    for (i = j = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
+        if (should_validate_capability(i) && s->enabled_capabilities[i]) {
+            state->capabilities[j++] = i;
+        }
+    }
+
     return 0;
 }
 
@@ -347,6 +386,40 @@ static int configuration_pre_load(void *opaque)
     return 0;
 }
 
+static bool configuration_validate_capabilities(SaveState *state)
+{
+    bool ret = true;
+    MigrationState *s = migrate_get_current();
+    unsigned long *source_caps_bm;
+    int i;
+
+    source_caps_bm = bitmap_new(MIGRATION_CAPABILITY__MAX);
+    for (i = 0; i < state->caps_count; i++) {
+        MigrationCapability capability = state->capabilities[i];
+        set_bit(capability, source_caps_bm);
+    }
+
+    for (i = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
+        bool source_state, target_state;
+        if (!should_validate_capability(i)) {
+            continue;
+        }
+        source_state = test_bit(i, source_caps_bm);
+        target_state = s->enabled_capabilities[i];
+        if (source_state != target_state) {
+            error_report("Capability %s is %s, but received capability is %s",
+                         MigrationCapability_str(i),
+                         target_state ? "on" : "off",
+                         source_state ? "on" : "off");
+            ret = false;
+            /* Don't break here to report all failed capabilities */
+        }
+    }
+
+    g_free(source_caps_bm);
+    return ret;
+}
+
 static int configuration_post_load(void *opaque, int version_id)
 {
     SaveState *state = opaque;
@@ -364,9 +437,53 @@ static int configuration_post_load(void *opaque, int version_id)
         return -EINVAL;
     }
 
+    if (!configuration_validate_capabilities(state)) {
+        return -EINVAL;
+    }
+
     return 0;
 }
 
+static int get_capability(QEMUFile *f, void *pv, size_t size,
+                          const VMStateField *field)
+{
+    MigrationCapability *capability = pv;
+    char capability_str[UINT8_MAX + 1];
+    uint8_t len;
+    int i;
+
+    len = qemu_get_byte(f);
+    qemu_get_buffer(f, (uint8_t *)capability_str, len);
+    capability_str[len] = '\0';
+    for (i = 0; i < MIGRATION_CAPABILITY__MAX; i++) {
+        if (!strcmp(MigrationCapability_str(i), capability_str)) {
+            *capability = i;
+            return 0;
+        }
+    }
+    error_report("Received unknown capability %s", capability_str);
+    return -EINVAL;
+}
+
+static int put_capability(QEMUFile *f, void *pv, size_t size,
+                          const VMStateField *field, QJSON *vmdesc)
+{
+    MigrationCapability *capability = pv;
+    const char *capability_str = MigrationCapability_str(*capability);
+    size_t len = strlen(capability_str);
+    assert(len <= UINT8_MAX);
+
+    qemu_put_byte(f, len);
+    qemu_put_buffer(f, (uint8_t *)capability_str, len);
+    return 0;
+}
+
+static const VMStateInfo vmstate_info_capability = {
+    .name = "capability",
+    .get  = get_capability,
+    .put  = put_capability,
+};
+
 /* The target-page-bits subsection is present only if the
  * target page size is not the same as the default (ie the
  * minimum page size for a variable-page-size guest CPU).
@@ -380,6 +497,11 @@ static bool vmstate_target_page_bits_needed(void *opaque)
         > qemu_target_page_bits_min();
 }
 
+static bool vmstate_capabilites_needed(void *opaque)
+{
+    return get_validatable_capabilities_count() > 0;
+}
+
 static const VMStateDescription vmstate_target_page_bits = {
     .name = "configuration/target-page-bits",
     .version_id = 1,
@@ -391,6 +513,20 @@ static const VMStateDescription vmstate_target_page_bits = {
     }
 };
 
+static const VMStateDescription vmstate_capabilites = {
+    .name = "configuration/capabilities",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = vmstate_capabilites_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32_V(caps_count, SaveState, 1),
+        VMSTATE_VARRAY_UINT32_ALLOC(capabilities, SaveState, caps_count, 1,
+                                    vmstate_info_capability,
+                                    MigrationCapability),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static const VMStateDescription vmstate_configuration = {
     .name = "configuration",
     .version_id = 1,
@@ -404,6 +540,7 @@ static const VMStateDescription vmstate_configuration = {
     },
     .subsections = (const VMStateDescription*[]) {
         &vmstate_target_page_bits,
+        &vmstate_capabilites,
         NULL
     }
 };
-- 
2.20.1