[Qemu-devel] [PATCH v2 04/13] kvm: add support to sync the page encryption state bitmap

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

The SEV VMs have concept of private and shared memory. The private memory
is encrypted with guest-specific key, while shared memory may be encrypted
with hyperivosr key. The KVM_GET_PAGE_ENC_BITMAP can be used to get a
bitmap indicating whether the guest page is private or shared. A private
page must be transmitted using the SEV migration commands.

Add a cpu_physical_memory_sync_encrypted_bitmap() which can be used to sync
the page encryption bitmap for a given memory region.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 accel/kvm/kvm-all.c     |  38 ++++++++++
 include/exec/ram_addr.h | 161 ++++++++++++++++++++++++++++++++++++++--
 include/exec/ramlist.h  |   3 +-
 migration/ram.c         |  28 ++++++-
 4 files changed, 222 insertions(+), 8 deletions(-)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 162a2d5085..c935e9366c 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -504,6 +504,37 @@ static int kvm_get_dirty_pages_log_range(MemoryRegionSection *section,
 
 #define ALIGN(x, y)  (((x)+(y)-1) & ~((y)-1))
 
+/* sync page_enc bitmap */
+static int kvm_sync_page_enc_bitmap(KVMMemoryListener *kml,
+                                    MemoryRegionSection *section,
+                                    KVMSlot *mem)
+{
+    unsigned long size;
+    KVMState *s = kvm_state;
+    struct kvm_page_enc_bitmap e = {};
+    ram_addr_t pages = int128_get64(section->size) / getpagesize();
+    ram_addr_t start = section->offset_within_region +
+                       memory_region_get_ram_addr(section->mr);
+
+    size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS),
+                 /*HOST_LONG_BITS*/ 64) / 8;
+    e.enc_bitmap = g_malloc0(size);
+    e.start_gfn = mem->start_addr >> TARGET_PAGE_BITS;
+    e.num_pages = pages;
+    if (kvm_vm_ioctl(s, KVM_GET_PAGE_ENC_BITMAP, &e) == -1) {
+        DPRINTF("KVM_GET_PAGE_ENC_BITMAP ioctl failed %d\n", errno);
+        g_free(e.enc_bitmap);
+        return 1;
+    }
+
+    cpu_physical_memory_set_encrypted_lebitmap(e.enc_bitmap,
+                                               start, pages);
+
+    g_free(e.enc_bitmap);
+
+    return 0;
+}
+
 /**
  * kvm_physical_sync_dirty_bitmap - Grab dirty bitmap from kernel space
  * This function updates qemu's dirty bitmap using
@@ -553,6 +584,13 @@ static int kvm_physical_sync_dirty_bitmap(KVMMemoryListener *kml,
         }
 
         kvm_get_dirty_pages_log_range(section, d.dirty_bitmap);
+
+        if (kvm_memcrypt_enabled() &&
+            kvm_sync_page_enc_bitmap(kml, section, mem)) {
+            g_free(d.dirty_bitmap);
+            return -1;
+        }
+
         g_free(d.dirty_bitmap);
     }
 
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index f96777bb99..6fc6864194 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -51,6 +51,8 @@ struct RAMBlock {
     unsigned long *unsentmap;
     /* bitmap of already received pages in postcopy */
     unsigned long *receivedmap;
+    /* bitmap of page encryption state for an encrypted guest */
+    unsigned long *encbmap;
 };
 
 static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
@@ -314,9 +316,41 @@ static inline void cpu_physical_memory_set_dirty_range(ram_addr_t start,
 }
 
 #if !defined(_WIN32)
-static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
+
+static inline void cpu_physical_memory_set_encrypted_range(ram_addr_t start,
+                                                           ram_addr_t length,
+                                                           unsigned long val)
+{
+    unsigned long end, page;
+    unsigned long * const *src;
+
+    if (length == 0) {
+        return;
+    }
+
+    end = TARGET_PAGE_ALIGN(start + length) >> TARGET_PAGE_BITS;
+    page = start >> TARGET_PAGE_BITS;
+
+    rcu_read_lock();
+
+    src = atomic_rcu_read(&ram_list.dirty_memory[DIRTY_MEMORY_ENCRYPTED])->blocks;
+
+    while (page < end) {
+        unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
+        unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
+        unsigned long num = MIN(end - page, DIRTY_MEMORY_BLOCK_SIZE - offset);
+
+        atomic_xchg(&src[idx][BIT_WORD(offset)], val);
+        page += num;
+    }
+
+    rcu_read_unlock();
+}
+
+static inline void cpu_physical_memory_set_dirty_enc_lebitmap(unsigned long *bitmap,
                                                           ram_addr_t start,
-                                                          ram_addr_t pages)
+                                                          ram_addr_t pages,
+                                                          bool enc_map)
 {
     unsigned long i, j;
     unsigned long page_number, c;
@@ -349,10 +383,14 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
             if (bitmap[k]) {
                 unsigned long temp = leul_to_cpu(bitmap[k]);
 
-                atomic_or(&blocks[DIRTY_MEMORY_MIGRATION][idx][offset], temp);
-                atomic_or(&blocks[DIRTY_MEMORY_VGA][idx][offset], temp);
-                if (tcg_enabled()) {
-                    atomic_or(&blocks[DIRTY_MEMORY_CODE][idx][offset], temp);
+                if (enc_map) {
+                    atomic_xchg(&blocks[DIRTY_MEMORY_ENCRYPTED][idx][offset], temp);
+                } else {
+                    atomic_or(&blocks[DIRTY_MEMORY_MIGRATION][idx][offset], temp);
+                    atomic_or(&blocks[DIRTY_MEMORY_VGA][idx][offset], temp);
+                    if (tcg_enabled()) {
+                        atomic_or(&blocks[DIRTY_MEMORY_CODE][idx][offset], temp);
+                    }
                 }
             }
 
@@ -372,6 +410,17 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
          * especially when most of the memory is not dirty.
          */
         for (i = 0; i < len; i++) {
+
+            /* If its encrypted bitmap update, then we need to copy the bitmap
+             * value as-is to the destination.
+             */
+            if (enc_map) {
+                cpu_physical_memory_set_encrypted_range(start + i * TARGET_PAGE_SIZE,
+                                                        TARGET_PAGE_SIZE * hpratio,
+                                                        leul_to_cpu(bitmap[i]));
+                continue;
+            }
+
             if (bitmap[i] != 0) {
                 c = leul_to_cpu(bitmap[i]);
                 do {
@@ -387,6 +436,21 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
         }
     }
 }
+
+static inline void cpu_physical_memory_set_encrypted_lebitmap(unsigned long *bitmap,
+                                                              ram_addr_t start,
+                                                              ram_addr_t pages)
+{
+    return cpu_physical_memory_set_dirty_enc_lebitmap(bitmap, start, pages, true);
+}
+
+static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
+                                                          ram_addr_t start,
+                                                          ram_addr_t pages)
+{
+    return cpu_physical_memory_set_dirty_enc_lebitmap(bitmap, start, pages, false);
+}
+
 #endif /* not _WIN32 */
 
 bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start,
@@ -406,6 +470,7 @@ static inline void cpu_physical_memory_clear_dirty_range(ram_addr_t start,
     cpu_physical_memory_test_and_clear_dirty(start, length, DIRTY_MEMORY_MIGRATION);
     cpu_physical_memory_test_and_clear_dirty(start, length, DIRTY_MEMORY_VGA);
     cpu_physical_memory_test_and_clear_dirty(start, length, DIRTY_MEMORY_CODE);
+    cpu_physical_memory_test_and_clear_dirty(start, length, DIRTY_MEMORY_ENCRYPTED);
 }
 
 
@@ -474,5 +539,89 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
 
     return num_dirty;
 }
+
+static inline bool cpu_physical_memory_test_encrypted(ram_addr_t start,
+                                                      ram_addr_t length)
+{
+    unsigned long end, page;
+    bool enc = false;
+    unsigned long * const *src;
+
+    if (length == 0) {
+        return enc;
+    }
+
+    end = TARGET_PAGE_ALIGN(start + length) >> TARGET_PAGE_BITS;
+    page = start >> TARGET_PAGE_BITS;
+
+    rcu_read_lock();
+
+    src = atomic_rcu_read(&ram_list.dirty_memory[DIRTY_MEMORY_ENCRYPTED])->blocks;
+
+    while (page < end) {
+        unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
+        unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
+        unsigned long num = MIN(end - page, DIRTY_MEMORY_BLOCK_SIZE - offset);
+
+        enc |= atomic_read(&src[idx][BIT_WORD(offset)]);
+        page += num;
+    }
+
+    rcu_read_unlock();
+
+    return enc;
+}
+
+static inline
+void cpu_physical_memory_sync_encrypted_bitmap(RAMBlock *rb,
+                                               ram_addr_t start,
+                                               ram_addr_t length)
+{
+    ram_addr_t addr;
+    unsigned long word = BIT_WORD((start + rb->offset) >> TARGET_PAGE_BITS);
+    unsigned long *dest = rb->encbmap;
+
+    /* start address and length is aligned at the start of a word? */
+    if (((word * BITS_PER_LONG) << TARGET_PAGE_BITS) ==
+         (start + rb->offset) &&
+        !(length & ((BITS_PER_LONG << TARGET_PAGE_BITS) - 1))) {
+        int k;
+        int nr = BITS_TO_LONGS(length >> TARGET_PAGE_BITS);
+        unsigned long * const *src;
+        unsigned long idx = (word * BITS_PER_LONG) / DIRTY_MEMORY_BLOCK_SIZE;
+        unsigned long offset = BIT_WORD((word * BITS_PER_LONG) %
+                                        DIRTY_MEMORY_BLOCK_SIZE);
+        unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
+
+        rcu_read_lock();
+
+        src = atomic_rcu_read(
+                &ram_list.dirty_memory[DIRTY_MEMORY_ENCRYPTED])->blocks;
+
+        for (k = page; k < page + nr; k++) {
+            unsigned long bits = atomic_read(&src[idx][offset]);
+            dest[k] = bits;
+
+            if (++offset >= BITS_TO_LONGS(DIRTY_MEMORY_BLOCK_SIZE)) {
+                offset = 0;
+                idx++;
+            }
+        }
+
+        rcu_read_unlock();
+    } else {
+        ram_addr_t offset = rb->offset;
+
+        for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) {
+            long k = (start + addr) >> TARGET_PAGE_BITS;
+            if (cpu_physical_memory_test_encrypted(start + addr + offset,
+                                                   TARGET_PAGE_SIZE)) {
+                set_bit(k, dest);
+            } else {
+                clear_bit(k, dest);
+            }
+        }
+    }
+}
 #endif
 #endif
diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
index bc4faa1b00..2a5eab8b11 100644
--- a/include/exec/ramlist.h
+++ b/include/exec/ramlist.h
@@ -11,7 +11,8 @@ typedef struct RAMBlockNotifier RAMBlockNotifier;
 #define DIRTY_MEMORY_VGA       0
 #define DIRTY_MEMORY_CODE      1
 #define DIRTY_MEMORY_MIGRATION 2
-#define DIRTY_MEMORY_NUM       3        /* num of dirty bits */
+#define DIRTY_MEMORY_ENCRYPTED 3
+#define DIRTY_MEMORY_NUM       4        /* num of dirty bits */
 
 /* The dirty memory bitmap is split into fixed-size blocks to allow growth
  * under RCU.  The bitmap for a block can be accessed as follows:
diff --git a/migration/ram.c b/migration/ram.c
index 3c8977d508..d179867e1b 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1680,6 +1680,9 @@ static void migration_bitmap_sync_range(RAMState *rs, RAMBlock *rb,
     rs->migration_dirty_pages +=
         cpu_physical_memory_sync_dirty_bitmap(rb, 0, length,
                                               &rs->num_dirty_pages_period);
+    if (kvm_memcrypt_enabled()) {
+        cpu_physical_memory_sync_encrypted_bitmap(rb, 0, length);
+    }
 }
 
 /**
@@ -2465,6 +2468,22 @@ static bool save_compress_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
     return false;
 }
 
+/**
+ * encrypted_test_bitmap: check if the page is encrypted
+ *
+ * Returns a bool indicating whether the page is encrypted.
+ */
+static bool encrypted_test_bitmap(RAMState *rs, RAMBlock *block,
+                                  unsigned long page)
+{
+    /* ROM devices contains the unencrypted data */
+    if (memory_region_is_rom(block->mr)) {
+        return false;
+    }
+
+    return test_bit(page, block->encbmap);
+}
+
 /**
  * ram_save_target_page: save one target page
  *
@@ -2491,7 +2510,8 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
      * will take care of accessing the guest memory and re-encrypt it
      * for the transport purposes.
      */
-     if (kvm_memcrypt_enabled()) {
+     if (kvm_memcrypt_enabled() &&
+         encrypted_test_bitmap(rs, pss->block, pss->page)) {
         return ram_save_encrypted_page(rs, pss, last_stage);
      }
 
@@ -2724,6 +2744,8 @@ static void ram_save_cleanup(void *opaque)
         block->bmap = NULL;
         g_free(block->unsentmap);
         block->unsentmap = NULL;
+        g_free(block->encbmap);
+        block->encbmap = NULL;
     }
 
     xbzrle_cleanup();
@@ -3251,6 +3273,10 @@ static void ram_list_init_bitmaps(void)
                 block->unsentmap = bitmap_new(pages);
                 bitmap_set(block->unsentmap, 0, pages);
             }
+            if (kvm_memcrypt_enabled()) {
+                block->encbmap = bitmap_new(pages);
+                bitmap_set(block->encbmap, 0, pages);
+            }
         }
     }
 }
-- 
2.17.1