[Qemu-devel] [PATCH v3 00/16] Postcopy: Hugepage support

[Qemu-devel] [PATCH v3 00/16] Postcopy: Hugepage support

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Hi,
  The existing postcopy code, and the userfault kernel
code that supports it, only works for normal anonymous memory.
Kernel support for userfault on hugetlbfs has just
been merged in Linus's tree for 4.11 (see 4c9a7831b11 merge)

Note that while this code supports arbitrary sized hugepages,
it doesn't make sense with pages above the few-MB region,
so while 2MB is fine, 1GB is probably a bad idea;
this code waits for and transmits whole huge pages, and a
1GB page would take about 1 second to transfer over a 10Gbps
link - which is way too long to pause the destination for.

Note: 'postcopy: Update userfaultfd.h header' is now from
Paolo's recent header update run; it can be dropped as
soon as Paolo's goes in.

Dave

v3
  Added an extra check in 'postcopy: Add extra check for COPY function'
  Updates from Laurent's review:
    moved the CONFIG_FALLOCATE_PUNCH_HOLE from 'ram_block_discard_range'
    into the following 'enhance ram_block_discard_range for hugepages'
    Merged the ram_block_discard_range / Fold postcopy_ram_discard_range
    into ram_discard_range  patches
    Removed the excess rcu_read_lock in ram_block_discard_range
    Removed a removal of a blank line in 'Mask fault address'
  Updated the 'Update userfaultfd.h header' - that's now from Paolo's update


Dr. David Alan Gilbert (16):
  postcopy: Transmit ram size summary word
  postcopy: Transmit and compare individual page sizes
  postcopy: Chunk discards for hugepages
  exec: ram_block_discard_range
  postcopy: enhance ram_block_discard_range for hugepages
  postcopy: Record largest page size
  postcopy: Plumb pagesize down into place helpers
  postcopy: Use temporary for placing zero huge pages
  postcopy: Load huge pages in one go
  postcopy: Mask fault addresses to huge page boundary
  postcopy: Send whole huge pages
  postcopy: Allow hugepages
  postcopy: Update userfaultfd.h header
  postcopy: Check for userfault+hugepage feature
  postcopy: Add doc about hugepages and postcopy
  postcopy: Add extra check for COPY function

 docs/migration.txt                |  13 ++++
 exec.c                            |  83 ++++++++++++++++++++++
 include/exec/cpu-common.h         |   2 +
 include/migration/migration.h     |   3 +
 include/migration/postcopy-ram.h  |  13 ++--
 linux-headers/linux/userfaultfd.h |  67 +++++++++++++++---
 migration/migration.c             |   1 +
 migration/postcopy-ram.c          | 142 ++++++++++++++++++--------------------
 migration/ram.c                   | 109 ++++++++++++++++++-----------
 migration/savevm.c                |  32 ++++++---
 migration/trace-events            |   2 +-
 11 files changed, 319 insertions(+), 148 deletions(-)

-- 
2.9.3

[Qemu-devel] [PATCH v3 01/16] postcopy: Transmit ram size summary word

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Replace the host page-size in the 'advise' command by a pagesize
summary bitmap; if the VM is just using normal RAM then
this will be exactly the same as before, however if they're using
huge pages they'll be different, and thus:
   a) Migration from/to old qemu's that don't understand huge pages
      will fail early.
   b) Migrations with different size RAMBlocks will also fail early.

This catches it very early; earlier than the detailed per-block
check in the next patch.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
 include/migration/migration.h |  1 +
 migration/ram.c               | 17 +++++++++++++++++
 migration/savevm.c            | 32 +++++++++++++++++++++-----------
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index 1735d66..aafa68f 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -375,6 +375,7 @@ void global_state_store_running(void);
 void flush_page_queue(MigrationState *ms);
 int ram_save_queue_pages(MigrationState *ms, const char *rbname,
                          ram_addr_t start, ram_addr_t len);
+uint64_t ram_pagesize_summary(void);
 
 PostcopyState postcopy_state_get(void);
 /* Set the state and return the old state */
diff --git a/migration/ram.c b/migration/ram.c
index f289fcd..1f6397a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -600,6 +600,23 @@ static void migration_bitmap_sync_init(void)
     iterations_prev = 0;
 }
 
+/* Returns a summary bitmap of the page sizes of all RAMBlocks;
+ * for VMs with just normal pages this is equivalent to the
+ * host page size.  If it's got some huge pages then it's the OR
+ * of all the different page sizes.
+ */
+uint64_t ram_pagesize_summary(void)
+{
+    RAMBlock *block;
+    uint64_t summary = 0;
+
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        summary |= block->page_size;
+    }
+
+    return summary;
+}
+
 static void migration_bitmap_sync(void)
 {
     RAMBlock *block;
diff --git a/migration/savevm.c b/migration/savevm.c
index 5ecd264..1c19fe5 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -869,7 +869,7 @@ int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len)
 void qemu_savevm_send_postcopy_advise(QEMUFile *f)
 {
     uint64_t tmp[2];
-    tmp[0] = cpu_to_be64(getpagesize());
+    tmp[0] = cpu_to_be64(ram_pagesize_summary());
     tmp[1] = cpu_to_be64(1ul << qemu_target_page_bits());
 
     trace_qemu_savevm_send_postcopy_advise();
@@ -1346,7 +1346,7 @@ static int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
 static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis)
 {
     PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_ADVISE);
-    uint64_t remote_hps, remote_tps;
+    uint64_t remote_pagesize_summary, local_pagesize_summary, remote_tps;
 
     trace_loadvm_postcopy_handle_advise();
     if (ps != POSTCOPY_INCOMING_NONE) {
@@ -1359,17 +1359,27 @@ static int loadvm_postcopy_handle_advise(MigrationIncomingState *mis)
         return -1;
     }
 
-    remote_hps = qemu_get_be64(mis->from_src_file);
-    if (remote_hps != getpagesize())  {
+    remote_pagesize_summary = qemu_get_be64(mis->from_src_file);
+    local_pagesize_summary = ram_pagesize_summary();
+
+    if (remote_pagesize_summary != local_pagesize_summary)  {
         /*
-         * Some combinations of mismatch are probably possible but it gets
-         * a bit more complicated.  In particular we need to place whole
-         * host pages on the dest at once, and we need to ensure that we
-         * handle dirtying to make sure we never end up sending part of
-         * a hostpage on it's own.
+         * This detects two potential causes of mismatch:
+         *   a) A mismatch in host page sizes
+         *      Some combinations of mismatch are probably possible but it gets
+         *      a bit more complicated.  In particular we need to place whole
+         *      host pages on the dest at once, and we need to ensure that we
+         *      handle dirtying to make sure we never end up sending part of
+         *      a hostpage on it's own.
+         *   b) The use of different huge page sizes on source/destination
+         *      a more fine grain test is performed during RAM block migration
+         *      but this test here causes a nice early clear failure, and
+         *      also fails when passed to an older qemu that doesn't
+         *      do huge pages.
          */
-        error_report("Postcopy needs matching host page sizes (s=%d d=%d)",
-                     (int)remote_hps, getpagesize());
+        error_report("Postcopy needs matching RAM page sizes (s=%" PRIx64
+                                                             " d=%" PRIx64 ")",
+                     remote_pagesize_summary, local_pagesize_summary);
         return -1;
     }
 
-- 
2.9.3

[Qemu-devel] [PATCH v3 02/16] postcopy: Transmit and compare individual page sizes

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When using postcopy with hugepages, we require the source
and destination page sizes for any RAMBlock to match; note
that different RAMBlocks in the same VM can have different
page sizes.

Transmit them as part of the RAM information header and
fail if there's a difference.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
 migration/ram.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index 1f6397a..fbd987a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2027,6 +2027,9 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
         qemu_put_byte(f, strlen(block->idstr));
         qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
         qemu_put_be64(f, block->used_length);
+        if (migrate_postcopy_ram() && block->page_size != qemu_host_page_size) {
+            qemu_put_be64(f, block->page_size);
+        }
     }
 
     rcu_read_unlock();
@@ -2528,6 +2531,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
      * be atomic
      */
     bool postcopy_running = postcopy_state_get() >= POSTCOPY_INCOMING_LISTENING;
+    /* ADVISE is earlier, it shows the source has the postcopy capability on */
+    bool postcopy_advised = postcopy_state_get() >= POSTCOPY_INCOMING_ADVISE;
 
     seq_iter++;
 
@@ -2592,6 +2597,18 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                             error_report_err(local_err);
                         }
                     }
+                    /* For postcopy we need to check hugepage sizes match */
+                    if (postcopy_advised &&
+                        block->page_size != qemu_host_page_size) {
+                        uint64_t remote_page_size = qemu_get_be64(f);
+                        if (remote_page_size != block->page_size) {
+                            error_report("Mismatched RAM page size %s "
+                                         "(local) %zd != %" PRId64,
+                                         id, block->page_size,
+                                         remote_page_size);
+                            ret = -EINVAL;
+                        }
+                    }
                     ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
                                           block->idstr);
                 } else {
-- 
2.9.3

[Qemu-devel] [PATCH v3 03/16] postcopy: Chunk discards for hugepages

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

At the start of the postcopy phase, partially sent huge pages
must be discarded.  The code for dealing with host page sizes larger
than the target page size can be reused for this case.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/ram.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index fbd987a..7c5cdf9 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1672,12 +1672,17 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
 {
     unsigned long *bitmap;
     unsigned long *unsentmap;
-    unsigned int host_ratio = qemu_host_page_size / TARGET_PAGE_SIZE;
+    unsigned int host_ratio = block->page_size / TARGET_PAGE_SIZE;
     unsigned long first = block->offset >> TARGET_PAGE_BITS;
     unsigned long len = block->used_length >> TARGET_PAGE_BITS;
     unsigned long last = first + (len - 1);
     unsigned long run_start;
 
+    if (block->page_size == TARGET_PAGE_SIZE) {
+        /* Easy case - TPS==HPS for a non-huge page RAMBlock */
+        return;
+    }
+
     bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
     unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
 
@@ -1781,7 +1786,8 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
  * Utility for the outgoing postcopy code.
  *
  * Discard any partially sent host-page size chunks, mark any partially
- * dirty host-page size chunks as all dirty.
+ * dirty host-page size chunks as all dirty.  In this case the host-page
+ * is the host-page for the particular RAMBlock, i.e. it might be a huge page
  *
  * Returns: 0 on success
  */
@@ -1789,11 +1795,6 @@ static int postcopy_chunk_hostpages(MigrationState *ms)
 {
     struct RAMBlock *block;
 
-    if (qemu_host_page_size == TARGET_PAGE_SIZE) {
-        /* Easy case - TPS==HPS - nothing to be done */
-        return 0;
-    }
-
     /* Easiest way to make sure we don't resume in the middle of a host-page */
     last_seen_block = NULL;
     last_sent_block = NULL;
@@ -1849,7 +1850,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
         return -EINVAL;
     }
 
-    /* Deal with TPS != HPS */
+    /* Deal with TPS != HPS and huge pages */
     ret = postcopy_chunk_hostpages(ms);
     if (ret) {
         rcu_read_unlock();
-- 
2.9.3

[Qemu-devel] [PATCH v3 04/16] exec: ram_block_discard_range

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Create ram_block_discard_range in exec.c to replace
postcopy_ram_discard_range and most of ram_discard_range.

Those two routines are a bit of a weird combination, and
ram_discard_range is about to get more complex for hugepages.
It's OS dependent code (so shouldn't be in migration/ram.c) but
it needs quite a bit of the innards of RAMBlock so doesn't belong in
the os*.c.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
 exec.c                           | 54 ++++++++++++++++++++++++++++++++++++++++
 include/exec/cpu-common.h        |  1 +
 include/migration/postcopy-ram.h |  7 ------
 migration/postcopy-ram.c         | 30 +---------------------
 migration/ram.c                  | 24 +++---------------
 migration/trace-events           |  2 +-
 6 files changed, 60 insertions(+), 58 deletions(-)

diff --git a/exec.c b/exec.c
index 865a1e8..ddbc314 100644
--- a/exec.c
+++ b/exec.c
@@ -45,6 +45,7 @@
 #include "exec/address-spaces.h"
 #include "sysemu/xen-mapcache.h"
 #include "trace-root.h"
+
 #endif
 #include "exec/cpu-all.h"
 #include "qemu/rcu_queue.h"
@@ -3288,4 +3289,57 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
     rcu_read_unlock();
     return ret;
 }
+
+/*
+ * Unmap pages of memory from start to start+length such that
+ * they a) read as 0, b) Trigger whatever fault mechanism
+ * the OS provides for postcopy.
+ * The pages must be unmapped by the end of the function.
+ * Returns: 0 on success, none-0 on failure
+ *
+ */
+int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
+{
+    int ret = -1;
+
+    uint8_t *host_startaddr = rb->host + start;
+
+    if ((uintptr_t)host_startaddr & (rb->page_size - 1)) {
+        error_report("ram_block_discard_range: Unaligned start address: %p",
+                     host_startaddr);
+        goto err;
+    }
+
+    if ((start + length) <= rb->used_length) {
+        uint8_t *host_endaddr = host_startaddr + length;
+        if ((uintptr_t)host_endaddr & (rb->page_size - 1)) {
+            error_report("ram_block_discard_range: Unaligned end address: %p",
+                         host_endaddr);
+            goto err;
+        }
+
+        errno = ENOTSUP; /* If we are missing MADVISE etc */
+
+#if defined(CONFIG_MADVISE)
+        /* Note: We need the madvise MADV_DONTNEED behaviour of definitely
+         * freeing the page.
+         */
+        ret = madvise(host_startaddr, length, MADV_DONTNEED);
+#endif
+        if (ret) {
+            ret = -errno;
+            error_report("ram_block_discard_range: Failed to discard range "
+                         "%s:%" PRIx64 " +%zx (%d)",
+                         rb->idstr, start, length, ret);
+        }
+    } else {
+        error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64
+                     "/%zx/" RAM_ADDR_FMT")",
+                     rb->idstr, start, length, rb->used_length);
+    }
+
+err:
+    return ret;
+}
+
 #endif
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index bd15853..1350c2e 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -105,6 +105,7 @@ typedef int (RAMBlockIterFunc)(const char *block_name, void *host_addr,
     ram_addr_t offset, ram_addr_t length, void *opaque);
 
 int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque);
+int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length);
 
 #endif
 
diff --git a/include/migration/postcopy-ram.h b/include/migration/postcopy-ram.h
index b6a7491f..43bbbca 100644
--- a/include/migration/postcopy-ram.h
+++ b/include/migration/postcopy-ram.h
@@ -35,13 +35,6 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
 
 /*
- * Discard the contents of 'length' bytes from 'start'
- * We can assume that if we've been called postcopy_ram_hosttest returned true
- */
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length);
-
-/*
  * Userfault requires us to mark RAM as NOHUGEPAGE prior to discard
  * however leaving it until after precopy means that most of the precopy
  * data is still THPd
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a40dddb..1e3d22f 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -200,27 +200,6 @@ out:
     return ret;
 }
 
-/**
- * postcopy_ram_discard_range: Discard a range of memory.
- * We can assume that if we've been called postcopy_ram_hosttest returned true.
- *
- * @mis: Current incoming migration state.
- * @start, @length: range of memory to discard.
- *
- * returns: 0 on success.
- */
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length)
-{
-    trace_postcopy_ram_discard_range(start, length);
-    if (madvise(start, length, MADV_DONTNEED)) {
-        error_report("%s MADV_DONTNEED: %s", __func__, strerror(errno));
-        return -1;
-    }
-
-    return 0;
-}
-
 /*
  * Setup an area of RAM so that it *can* be used for postcopy later; this
  * must be done right at the start prior to pre-copy.
@@ -239,7 +218,7 @@ static int init_range(const char *block_name, void *host_addr,
      * - we're going to get the copy from the source anyway.
      * (Precopy will just overwrite this data, so doesn't need the discard)
      */
-    if (postcopy_ram_discard_range(mis, host_addr, length)) {
+    if (ram_discard_range(mis, block_name, 0, length)) {
         return -1;
     }
 
@@ -658,13 +637,6 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
     return -1;
 }
 
-int postcopy_ram_discard_range(MigrationIncomingState *mis, uint8_t *start,
-                               size_t length)
-{
-    assert(0);
-    return -1;
-}
-
 int postcopy_ram_prepare_discard(MigrationIncomingState *mis)
 {
     assert(0);
diff --git a/migration/ram.c b/migration/ram.c
index 7c5cdf9..44fe960 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1890,6 +1890,8 @@ int ram_discard_range(MigrationIncomingState *mis,
 {
     int ret = -1;
 
+    trace_ram_discard_range(block_name, start, length);
+
     rcu_read_lock();
     RAMBlock *rb = qemu_ram_block_by_name(block_name);
 
@@ -1899,27 +1901,7 @@ int ram_discard_range(MigrationIncomingState *mis,
         goto err;
     }
 
-    uint8_t *host_startaddr = rb->host + start;
-
-    if ((uintptr_t)host_startaddr & (qemu_host_page_size - 1)) {
-        error_report("ram_discard_range: Unaligned start address: %p",
-                     host_startaddr);
-        goto err;
-    }
-
-    if ((start + length) <= rb->used_length) {
-        uint8_t *host_endaddr = host_startaddr + length;
-        if ((uintptr_t)host_endaddr & (qemu_host_page_size - 1)) {
-            error_report("ram_discard_range: Unaligned end address: %p",
-                         host_endaddr);
-            goto err;
-        }
-        ret = postcopy_ram_discard_range(mis, host_startaddr, length);
-    } else {
-        error_report("ram_discard_range: Overrun block '%s' (%" PRIu64
-                     "/%zx/" RAM_ADDR_FMT")",
-                     block_name, start, length, rb->used_length);
-    }
+    ret = ram_block_discard_range(rb, start, length);
 
 err:
     rcu_read_unlock();
diff --git a/migration/trace-events b/migration/trace-events
index fa660e3..7372ce2 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -68,6 +68,7 @@ get_queued_page_not_dirty(const char *block_name, uint64_t tmp_offset, uint64_t
 migration_bitmap_sync_start(void) ""
 migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64
 migration_throttle(void) ""
+ram_discard_range(const char *rbname, uint64_t start, size_t len) "%s: start: %" PRIx64 " %zx"
 ram_load_postcopy_loop(uint64_t addr, int flags) "@%" PRIx64 " %x"
 ram_postcopy_send_discard_bitmap(void) ""
 ram_save_queue_pages(const char *rbname, size_t start, size_t len) "%s: start: %zx len: %zx"
@@ -176,7 +177,6 @@ rdma_start_outgoing_migration_after_rdma_source_init(void) ""
 # migration/postcopy-ram.c
 postcopy_discard_send_finish(const char *ramblock, int nwords, int ncmds) "%s mask words sent=%d in %d commands"
 postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned long length) "%s:%lx/%lx"
-postcopy_ram_discard_range(void *start, size_t length) "%p,+%zx"
 postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
 postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
 postcopy_nhp_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"
-- 
2.9.3

Re: [Qemu-devel] [PATCH v3 04/16] exec: ram_block_discard_range

[Laurent Vivier]

On 24/02/2017 19:28, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Create ram_block_discard_range in exec.c to replace
> postcopy_ram_discard_range and most of ram_discard_range.
> 
> Those two routines are a bit of a weird combination, and
> ram_discard_range is about to get more complex for hugepages.
> It's OS dependent code (so shouldn't be in migration/ram.c) but
> it needs quite a bit of the innards of RAMBlock so doesn't belong in
> the os*.c.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> ---
>  exec.c                           | 54 ++++++++++++++++++++++++++++++++++++++++
>  include/exec/cpu-common.h        |  1 +
>  include/migration/postcopy-ram.h |  7 ------
>  migration/postcopy-ram.c         | 30 +---------------------
>  migration/ram.c                  | 24 +++---------------
>  migration/trace-events           |  2 +-
>  6 files changed, 60 insertions(+), 58 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 865a1e8..ddbc314 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -45,6 +45,7 @@
>  #include "exec/address-spaces.h"
>  #include "sysemu/xen-mapcache.h"
>  #include "trace-root.h"
> +
>  #endif

It seems a blank line has "migrated" here from PATCH v2 11/16. ;)

Reviewed-by: Laurent Vivier <lvivier@redhat.com>

[Qemu-devel] [PATCH v3 05/16] postcopy: enhance ram_block_discard_range for hugepages

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Unfortunately madvise DONTNEED doesn't work on hugepagetlb
so use fallocate(FALLOC_FL_PUNCH_HOLE)
qemu_fd_getpagesize only sets the page based off a file
if the file is from hugetlbfs.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 exec.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/exec.c b/exec.c
index ddbc314..ec3a11f 100644
--- a/exec.c
+++ b/exec.c
@@ -46,6 +46,11 @@
 #include "sysemu/xen-mapcache.h"
 #include "trace-root.h"
 
+#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
+#include <fcntl.h>
+#include <linux/falloc.h>
+#endif
+
 #endif
 #include "exec/cpu-all.h"
 #include "qemu/rcu_queue.h"
@@ -3320,12 +3325,23 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
 
         errno = ENOTSUP; /* If we are missing MADVISE etc */
 
+        if (rb->page_size == qemu_host_page_size) {
 #if defined(CONFIG_MADVISE)
-        /* Note: We need the madvise MADV_DONTNEED behaviour of definitely
-         * freeing the page.
-         */
-        ret = madvise(host_startaddr, length, MADV_DONTNEED);
+            /* Note: We need the madvise MADV_DONTNEED behaviour of definitely
+             * freeing the page.
+             */
+            ret = madvise(host_startaddr, length, MADV_DONTNEED);
 #endif
+        } else {
+            /* Huge page case  - unfortunately it can't do DONTNEED, but
+             * it can do the equivalent by FALLOC_FL_PUNCH_HOLE in the
+             * huge page file.
+             */
+#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
+            ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+                            start, length);
+#endif
+        }
         if (ret) {
             ret = -errno;
             error_report("ram_block_discard_range: Failed to discard range "
-- 
2.9.3

[Qemu-devel] [PATCH v3 06/16] postcopy: Record largest page size

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Record the largest page size in use; we'll need it soon for allocating
temporary buffers.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 exec.c                        | 13 +++++++++++++
 include/exec/cpu-common.h     |  1 +
 include/migration/migration.h |  1 +
 migration/migration.c         |  1 +
 4 files changed, 16 insertions(+)

diff --git a/exec.c b/exec.c
index ec3a11f..099794a 100644
--- a/exec.c
+++ b/exec.c
@@ -1524,6 +1524,19 @@ size_t qemu_ram_pagesize(RAMBlock *rb)
     return rb->page_size;
 }
 
+/* Returns the largest size of page in use */
+size_t qemu_ram_pagesize_largest(void)
+{
+    RAMBlock *block;
+    size_t largest = 0;
+
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        largest = MAX(largest, qemu_ram_pagesize(block));
+    }
+
+    return largest;
+}
+
 static int memory_try_enable_merging(void *addr, size_t len)
 {
     if (!machine_mem_merge(current_machine)) {
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 1350c2e..8c305aa 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -64,6 +64,7 @@ void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev);
 void qemu_ram_unset_idstr(RAMBlock *block);
 const char *qemu_ram_get_idstr(RAMBlock *rb);
 size_t qemu_ram_pagesize(RAMBlock *block);
+size_t qemu_ram_pagesize_largest(void);
 
 void cpu_physical_memory_rw(hwaddr addr, uint8_t *buf,
                             int len, int is_write);
diff --git a/include/migration/migration.h b/include/migration/migration.h
index aafa68f..e8e2a7f 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -92,6 +92,7 @@ struct MigrationIncomingState {
      */
     QemuEvent main_thread_load_event;
 
+    size_t         largest_page_size;
     bool           have_fault_thread;
     QemuThread     fault_thread;
     QemuSemaphore  fault_thread_sem;
diff --git a/migration/migration.c b/migration/migration.c
index c6ae69d..869697e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -383,6 +383,7 @@ static void process_incoming_migration_co(void *opaque)
     int ret;
 
     mis->from_src_file = f;
+    mis->largest_page_size = qemu_ram_pagesize_largest();
     postcopy_state_set(POSTCOPY_INCOMING_NONE);
     migrate_set_state(&mis->state, MIGRATION_STATUS_NONE,
                       MIGRATION_STATUS_ACTIVE);
-- 
2.9.3

[Qemu-devel] [PATCH v3 07/16] postcopy: Plumb pagesize down into place helpers

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Now we deal with normal size pages and huge pages we need
to tell the place handlers the size we're dealing with
and make sure the temporary page is large enough.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 include/migration/postcopy-ram.h |  6 +++--
 migration/postcopy-ram.c         | 47 ++++++++++++++++++++++++----------------
 migration/ram.c                  | 15 +++++++------
 3 files changed, 40 insertions(+), 28 deletions(-)

diff --git a/include/migration/postcopy-ram.h b/include/migration/postcopy-ram.h
index 43bbbca..8e036b9 100644
--- a/include/migration/postcopy-ram.h
+++ b/include/migration/postcopy-ram.h
@@ -74,13 +74,15 @@ void postcopy_discard_send_finish(MigrationState *ms,
  *    to use other postcopy_ routines to allocate.
  * returns 0 on success
  */
-int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);
+int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
+                        size_t pagesize);
 
 /*
  * Place a zero page at (host) atomically
  * returns 0 on success
  */
-int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);
+int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
+                             size_t pagesize);
 
 /*
  * Allocate a page of memory that can be mapped at a later point in time
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 1e3d22f..a8b7fed 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -321,7 +321,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
     migrate_send_rp_shut(mis, qemu_file_get_error(mis->from_src_file) != 0);
 
     if (mis->postcopy_tmp_page) {
-        munmap(mis->postcopy_tmp_page, getpagesize());
+        munmap(mis->postcopy_tmp_page, mis->largest_page_size);
         mis->postcopy_tmp_page = NULL;
     }
     trace_postcopy_ram_incoming_cleanup_exit();
@@ -543,13 +543,14 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
  * Place a host page (from) at (host) atomically
  * returns 0 on success
  */
-int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
+int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
+                        size_t pagesize)
 {
     struct uffdio_copy copy_struct;
 
     copy_struct.dst = (uint64_t)(uintptr_t)host;
     copy_struct.src = (uint64_t)(uintptr_t)from;
-    copy_struct.len = getpagesize();
+    copy_struct.len = pagesize;
     copy_struct.mode = 0;
 
     /* copy also acks to the kernel waking the stalled thread up
@@ -559,8 +560,8 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
      */
     if (ioctl(mis->userfault_fd, UFFDIO_COPY, &copy_struct)) {
         int e = errno;
-        error_report("%s: %s copy host: %p from: %p",
-                     __func__, strerror(e), host, from);
+        error_report("%s: %s copy host: %p from: %p (size: %zd)",
+                     __func__, strerror(e), host, from, pagesize);
 
         return -e;
     }
@@ -573,23 +574,29 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
  * Place a zero page at (host) atomically
  * returns 0 on success
  */
-int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
+int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
+                             size_t pagesize)
 {
-    struct uffdio_zeropage zero_struct;
+    trace_postcopy_place_page_zero(host);
 
-    zero_struct.range.start = (uint64_t)(uintptr_t)host;
-    zero_struct.range.len = getpagesize();
-    zero_struct.mode = 0;
+    if (pagesize == getpagesize()) {
+        struct uffdio_zeropage zero_struct;
+        zero_struct.range.start = (uint64_t)(uintptr_t)host;
+        zero_struct.range.len = getpagesize();
+        zero_struct.mode = 0;
 
-    if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
-        int e = errno;
-        error_report("%s: %s zero host: %p",
-                     __func__, strerror(e), host);
+        if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {
+            int e = errno;
+            error_report("%s: %s zero host: %p",
+                         __func__, strerror(e), host);
 
-        return -e;
+            return -e;
+        }
+    } else {
+        /* TODO: The kernel can't use UFFDIO_ZEROPAGE for hugepages */
+        assert(0);
     }
 
-    trace_postcopy_place_page_zero(host);
     return 0;
 }
 
@@ -604,7 +611,7 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
 void *postcopy_get_tmp_page(MigrationIncomingState *mis)
 {
     if (!mis->postcopy_tmp_page) {
-        mis->postcopy_tmp_page = mmap(NULL, getpagesize(),
+        mis->postcopy_tmp_page = mmap(NULL, mis->largest_page_size,
                              PROT_READ | PROT_WRITE, MAP_PRIVATE |
                              MAP_ANONYMOUS, -1, 0);
         if (mis->postcopy_tmp_page == MAP_FAILED) {
@@ -649,13 +656,15 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
     return -1;
 }
 
-int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)
+int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from,
+                        size_t pagesize)
 {
     assert(0);
     return -1;
 }
 
-int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)
+int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
+                        size_t pagesize)
 {
     assert(0);
     return -1;
diff --git a/migration/ram.c b/migration/ram.c
index 44fe960..ff86664 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2402,6 +2402,7 @@ static int ram_load_postcopy(QEMUFile *f)
         void *host = NULL;
         void *page_buffer = NULL;
         void *place_source = NULL;
+        RAMBlock *block = NULL;
         uint8_t ch;
 
         addr = qemu_get_be64(f);
@@ -2411,7 +2412,7 @@ static int ram_load_postcopy(QEMUFile *f)
         trace_ram_load_postcopy_loop((uint64_t)addr, flags);
         place_needed = false;
         if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) {
-            RAMBlock *block = ram_block_from_stream(f, flags);
+            block = ram_block_from_stream(f, flags);
 
             host = host_from_ram_block_offset(block, addr);
             if (!host) {
@@ -2486,14 +2487,14 @@ static int ram_load_postcopy(QEMUFile *f)
 
         if (place_needed) {
             /* This gets called at the last target page in the host page */
+            void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
+
             if (all_zero) {
-                ret = postcopy_place_page_zero(mis,
-                                               host + TARGET_PAGE_SIZE -
-                                               qemu_host_page_size);
+                ret = postcopy_place_page_zero(mis, place_dest,
+                                               block->page_size);
             } else {
-                ret = postcopy_place_page(mis, host + TARGET_PAGE_SIZE -
-                                               qemu_host_page_size,
-                                               place_source);
+                ret = postcopy_place_page(mis, place_dest,
+                                          place_source, block->page_size);
             }
         }
         if (!ret) {
-- 
2.9.3

[Qemu-devel] [PATCH v3 08/16] postcopy: Use temporary for placing zero huge pages

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The kernel can't do UFFDIO_ZEROPAGE for huge pages, so we have
to allocate a temporary (always zero) page and use UFFDIO_COPYPAGE
on it.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 include/migration/migration.h |  1 +
 migration/postcopy-ram.c      | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index e8e2a7f..cbfe79c 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -108,6 +108,7 @@ struct MigrationIncomingState {
     QEMUFile *to_src_file;
     QemuMutex rp_mutex;    /* We send replies from multiple threads */
     void     *postcopy_tmp_page;
+    void     *postcopy_tmp_zero_page;
 
     QEMUBH *bh;
 
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a8b7fed..4c736d2 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -324,6 +324,10 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
         munmap(mis->postcopy_tmp_page, mis->largest_page_size);
         mis->postcopy_tmp_page = NULL;
     }
+    if (mis->postcopy_tmp_zero_page) {
+        munmap(mis->postcopy_tmp_zero_page, mis->largest_page_size);
+        mis->postcopy_tmp_zero_page = NULL;
+    }
     trace_postcopy_ram_incoming_cleanup_exit();
     return 0;
 }
@@ -593,8 +597,23 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host,
             return -e;
         }
     } else {
-        /* TODO: The kernel can't use UFFDIO_ZEROPAGE for hugepages */
-        assert(0);
+        /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */
+        if (!mis->postcopy_tmp_zero_page) {
+            mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
+                                               PROT_READ | PROT_WRITE,
+                                               MAP_PRIVATE | MAP_ANONYMOUS,
+                                               -1, 0);
+            if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
+                int e = errno;
+                mis->postcopy_tmp_zero_page = NULL;
+                error_report("%s: %s mapping large zero page",
+                             __func__, strerror(e));
+                return -e;
+            }
+            memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
+        }
+        return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
+                                   pagesize);
     }
 
     return 0;
-- 
2.9.3

[Qemu-devel] [PATCH v3 09/16] postcopy: Load huge pages in one go

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The existing postcopy RAM load loop already ensures that it
glues together whole host-pages from the target page size chunks sent
over the wire.  Modify the definition of host page that it uses
to be the RAM block page size and thus be huge pages where appropriate.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/ram.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index ff86664..9f28da2 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2390,7 +2390,7 @@ static int ram_load_postcopy(QEMUFile *f)
 {
     int flags = 0, ret = 0;
     bool place_needed = false;
-    bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE;
+    bool matching_page_sizes = false;
     MigrationIncomingState *mis = migration_incoming_get_current();
     /* Temporary page that is later 'placed' */
     void *postcopy_host_page = postcopy_get_tmp_page(mis);
@@ -2420,8 +2420,11 @@ static int ram_load_postcopy(QEMUFile *f)
                 ret = -EINVAL;
                 break;
             }
+            matching_page_sizes = block->page_size == TARGET_PAGE_SIZE;
             /*
-             * Postcopy requires that we place whole host pages atomically.
+             * Postcopy requires that we place whole host pages atomically;
+             * these may be huge pages for RAMBlocks that are backed by
+             * hugetlbfs.
              * To make it atomic, the data is read into a temporary page
              * that's moved into place later.
              * The migration protocol uses,  possibly smaller, target-pages
@@ -2429,9 +2432,9 @@ static int ram_load_postcopy(QEMUFile *f)
              * of a host page in order.
              */
             page_buffer = postcopy_host_page +
-                          ((uintptr_t)host & ~qemu_host_page_mask);
+                          ((uintptr_t)host & (block->page_size - 1));
             /* If all TP are zero then we can optimise the place */
-            if (!((uintptr_t)host & ~qemu_host_page_mask)) {
+            if (!((uintptr_t)host & (block->page_size - 1))) {
                 all_zero = true;
             } else {
                 /* not the 1st TP within the HP */
@@ -2449,7 +2452,7 @@ static int ram_load_postcopy(QEMUFile *f)
              * page
              */
             place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
-                                     ~qemu_host_page_mask) == 0;
+                                     (block->page_size - 1)) == 0;
             place_source = postcopy_host_page;
         }
         last_host = host;
-- 
2.9.3

[Qemu-devel] [PATCH v3 10/16] postcopy: Mask fault addresses to huge page boundary

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Currently the fault address received by userfault is rounded to
the host page boundary and a host page is requested from the source.
Use the current RAMBlock page size instead of the general host page
size so that for RAMBlocks backed by huge pages we request the whole
huge page.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/postcopy-ram.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 4c736d2..03cbd6e 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -403,7 +403,6 @@ static void *postcopy_ram_fault_thread(void *opaque)
     MigrationIncomingState *mis = opaque;
     struct uffd_msg msg;
     int ret;
-    size_t hostpagesize = getpagesize();
     RAMBlock *rb = NULL;
     RAMBlock *last_rb = NULL; /* last RAMBlock we sent part of */
 
@@ -470,7 +469,7 @@ static void *postcopy_ram_fault_thread(void *opaque)
             break;
         }
 
-        rb_offset &= ~(hostpagesize - 1);
+        rb_offset &= ~(qemu_ram_pagesize(rb) - 1);
         trace_postcopy_ram_fault_thread_request(msg.arg.pagefault.address,
                                                 qemu_ram_get_idstr(rb),
                                                 rb_offset);
@@ -482,11 +481,11 @@ static void *postcopy_ram_fault_thread(void *opaque)
         if (rb != last_rb) {
             last_rb = rb;
             migrate_send_rp_req_pages(mis, qemu_ram_get_idstr(rb),
-                                     rb_offset, hostpagesize);
+                                     rb_offset, qemu_ram_pagesize(rb));
         } else {
             /* Save some space */
             migrate_send_rp_req_pages(mis, NULL,
-                                     rb_offset, hostpagesize);
+                                     rb_offset, qemu_ram_pagesize(rb));
         }
     }
     trace_postcopy_ram_fault_thread_exit();
-- 
2.9.3

[Qemu-devel] [PATCH v3 11/16] postcopy: Send whole huge pages

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The RAM save code uses ram_save_host_page to send whole
host pages at a time;  change this to use the host page size associated
with the RAM Block which may be a huge page.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/ram.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 9f28da2..719425b 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1302,6 +1302,8 @@ static int ram_save_target_page(MigrationState *ms, QEMUFile *f,
  *                     offset to point into the middle of a host page
  *                     in which case the remainder of the hostpage is sent.
  *                     Only dirty target pages are sent.
+ *                     Note that the host page size may be a huge page for this
+ *                     block.
  *
  * Returns: Number of pages written.
  *
@@ -1320,6 +1322,8 @@ static int ram_save_host_page(MigrationState *ms, QEMUFile *f,
                               ram_addr_t dirty_ram_abs)
 {
     int tmppages, pages = 0;
+    size_t pagesize = qemu_ram_pagesize(pss->block);
+
     do {
         tmppages = ram_save_target_page(ms, f, pss, last_stage,
                                         bytes_transferred, dirty_ram_abs);
@@ -1330,7 +1334,7 @@ static int ram_save_host_page(MigrationState *ms, QEMUFile *f,
         pages += tmppages;
         pss->offset += TARGET_PAGE_SIZE;
         dirty_ram_abs += TARGET_PAGE_SIZE;
-    } while (pss->offset & (qemu_host_page_size - 1));
+    } while (pss->offset & (pagesize - 1));
 
     /* The offset we leave with is the last one we looked at */
     pss->offset -= TARGET_PAGE_SIZE;
-- 
2.9.3

[Qemu-devel] [PATCH v3 12/16] postcopy: Allow hugepages

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Allow huge pages in postcopy.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/postcopy-ram.c | 25 +------------------------
 1 file changed, 1 insertion(+), 24 deletions(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 03cbd6e..6b30b43 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -85,24 +85,6 @@ static bool ufd_version_check(int ufd)
 }
 
 /*
- * Check for things that postcopy won't support; returns 0 if the block
- * is fine.
- */
-static int check_range(const char *block_name, void *host_addr,
-                      ram_addr_t offset, ram_addr_t length, void *opaque)
-{
-    RAMBlock *rb = qemu_ram_block_by_name(block_name);
-
-    if (qemu_ram_pagesize(rb) > getpagesize()) {
-        error_report("Postcopy doesn't support large page sizes yet (%s)",
-                     block_name);
-        return -E2BIG;
-    }
-
-    return 0;
-}
-
-/*
  * Note: This has the side effect of munlock'ing all of RAM, that's
  * normally fine since if the postcopy succeeds it gets turned back on at the
  * end.
@@ -122,12 +104,6 @@ bool postcopy_ram_supported_by_host(void)
         goto out;
     }
 
-    /* Check for anything about the RAMBlocks we don't support */
-    if (qemu_ram_foreach_block(check_range, NULL)) {
-        /* check_range will have printed its own error */
-        goto out;
-    }
-
     ufd = syscall(__NR_userfaultfd, O_CLOEXEC);
     if (ufd == -1) {
         error_report("%s: userfaultfd not available: %s", __func__,
@@ -139,6 +115,7 @@ bool postcopy_ram_supported_by_host(void)
     if (!ufd_version_check(ufd)) {
         goto out;
     }
+    /* TODO: Only allow huge pages if the kernel supports it */
 
     /*
      * userfault and mlock don't go together; we'll put it back later if
-- 
2.9.3

[Qemu-devel] [PATCH v3 13/16] postcopy: Update userfaultfd.h header

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Just the userfaultfd.h update from Paolo's header
update run;

* Drop this patch after Paolo's update goes in *

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 linux-headers/linux/userfaultfd.h | 67 +++++++++++++++++++++++++++++++++------
 1 file changed, 58 insertions(+), 9 deletions(-)

diff --git a/linux-headers/linux/userfaultfd.h b/linux-headers/linux/userfaultfd.h
index 19e8453..2ed5dc3 100644
--- a/linux-headers/linux/userfaultfd.h
+++ b/linux-headers/linux/userfaultfd.h
@@ -11,13 +11,18 @@
 
 #include <linux/types.h>
 
-#define UFFD_API ((__u64)0xAA)
 /*
- * After implementing the respective features it will become:
- * #define UFFD_API_FEATURES (UFFD_FEATURE_PAGEFAULT_FLAG_WP | \
- *			      UFFD_FEATURE_EVENT_FORK)
+ * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and
+ * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR.  In
+ * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ
+ * means the userland is reading).
  */
-#define UFFD_API_FEATURES (0)
+#define UFFD_API ((__u64)0xAA)
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |		\
+			   UFFD_FEATURE_EVENT_REMAP |		\
+			   UFFD_FEATURE_EVENT_MADVDONTNEED |	\
+			   UFFD_FEATURE_MISSING_HUGETLBFS |	\
+			   UFFD_FEATURE_MISSING_SHMEM)
 #define UFFD_API_IOCTLS				\
 	((__u64)1 << _UFFDIO_REGISTER |		\
 	 (__u64)1 << _UFFDIO_UNREGISTER |	\
@@ -26,6 +31,9 @@
 	((__u64)1 << _UFFDIO_WAKE |		\
 	 (__u64)1 << _UFFDIO_COPY |		\
 	 (__u64)1 << _UFFDIO_ZEROPAGE)
+#define UFFD_API_RANGE_IOCTLS_BASIC		\
+	((__u64)1 << _UFFDIO_WAKE |		\
+	 (__u64)1 << _UFFDIO_COPY)
 
 /*
  * Valid ioctl command number range with this API is from 0x00 to
@@ -72,6 +80,21 @@ struct uffd_msg {
 		} pagefault;
 
 		struct {
+			__u32	ufd;
+		} fork;
+
+		struct {
+			__u64	from;
+			__u64	to;
+			__u64	len;
+		} remap;
+
+		struct {
+			__u64	start;
+			__u64	end;
+		} madv_dn;
+
+		struct {
 			/* unused reserved fields */
 			__u64	reserved1;
 			__u64	reserved2;
@@ -84,9 +107,9 @@ struct uffd_msg {
  * Start at 0x12 and not at 0 to be more strict against bugs.
  */
 #define UFFD_EVENT_PAGEFAULT	0x12
-#if 0 /* not available yet */
 #define UFFD_EVENT_FORK		0x13
-#endif
+#define UFFD_EVENT_REMAP	0x14
+#define UFFD_EVENT_MADVDONTNEED	0x15
 
 /* flags for UFFD_EVENT_PAGEFAULT */
 #define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
@@ -104,11 +127,37 @@ struct uffdio_api {
 	 * Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
 	 * are to be considered implicitly always enabled in all kernels as
 	 * long as the uffdio_api.api requested matches UFFD_API.
+	 *
+	 * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
+	 * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
+	 * hugetlbfs virtual memory ranges. Adding or not adding
+	 * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
+	 * no real functional effect after UFFDIO_API returns, but
+	 * it's only useful for an initial feature set probe at
+	 * UFFDIO_API time. There are two ways to use it:
+	 *
+	 * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
+	 *    uffdio_api.features before calling UFFDIO_API, an error
+	 *    will be returned by UFFDIO_API on a kernel without
+	 *    hugetlbfs missing support
+	 *
+	 * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
+	 *    uffdio_api.features and instead it will be set by the
+	 *    kernel in the uffdio_api.features if the kernel supports
+	 *    it, so userland can later check if the feature flag is
+	 *    present in uffdio_api.features after UFFDIO_API
+	 *    succeeded.
+	 *
+	 * UFFD_FEATURE_MISSING_SHMEM works the same as
+	 * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
+	 * (i.e. tmpfs and other shmem based APIs).
 	 */
-#if 0 /* not available yet */
 #define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)
 #define UFFD_FEATURE_EVENT_FORK			(1<<1)
-#endif
+#define UFFD_FEATURE_EVENT_REMAP		(1<<2)
+#define UFFD_FEATURE_EVENT_MADVDONTNEED		(1<<3)
+#define UFFD_FEATURE_MISSING_HUGETLBFS		(1<<4)
+#define UFFD_FEATURE_MISSING_SHMEM		(1<<5)
 	__u64 features;
 
 	__u64 ioctls;
-- 
2.9.3

[Qemu-devel] [PATCH v3 14/16] postcopy: Check for userfault+hugepage feature

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

We need extra Linux kernel support (~4.11) to support userfaults
on hugetlbfs; check for them.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 migration/postcopy-ram.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 6b30b43..102fb61 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -81,6 +81,17 @@ static bool ufd_version_check(int ufd)
         return false;
     }
 
+    if (getpagesize() != ram_pagesize_summary()) {
+        bool have_hp = false;
+        /* We've got a huge page */
+#ifdef UFFD_FEATURE_MISSING_HUGETLBFS
+        have_hp = api_struct.features & UFFD_FEATURE_MISSING_HUGETLBFS;
+#endif
+        if (!have_hp) {
+            error_report("Userfault on this host does not support huge pages");
+            return false;
+        }
+    }
     return true;
 }
 
@@ -115,7 +126,6 @@ bool postcopy_ram_supported_by_host(void)
     if (!ufd_version_check(ufd)) {
         goto out;
     }
-    /* TODO: Only allow huge pages if the kernel supports it */
 
     /*
      * userfault and mlock don't go together; we'll put it back later if
-- 
2.9.3

[Qemu-devel] [PATCH v3 15/16] postcopy: Add doc about hugepages and postcopy

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
---
 docs/migration.txt | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/docs/migration.txt b/docs/migration.txt
index 6503c17..b462ead 100644
--- a/docs/migration.txt
+++ b/docs/migration.txt
@@ -482,3 +482,16 @@ request for a page that has already been sent is ignored.  Duplicate requests
 such as this can happen as a page is sent at about the same time the
 destination accesses it.
 
+=== Postcopy with hugepages ===
+
+Postcopy now works with hugetlbfs backed memory:
+  a) The linux kernel on the destination must support userfault on hugepages.
+  b) The huge-page configuration on the source and destination VMs must be
+     identical; i.e. RAMBlocks on both sides must use the same page size.
+  c) Note that -mem-path /dev/hugepages  will fall back to allocating normal
+     RAM if it doesn't have enough hugepages, triggering (b) to fail.
+     Using -mem-prealloc enforces the allocation using hugepages.
+  d) Care should be taken with the size of hugepage used; postcopy with 2MB
+     hugepages works well, however 1GB hugepages are likely to be problematic
+     since it takes ~1 second to transfer a 1GB hugepage across a 10Gbps link,
+     and until the full page is transferred the destination thread is blocked.
-- 
2.9.3

[Qemu-devel] [PATCH v3 16/16] postcopy: Add extra check for COPY function

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

As an extra sanity check, make sure the region we're registering
can perform UFFDIO_COPY;  the COPY will fail later but this
gives a cleaner failure.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/postcopy-ram.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 102fb61..effbeb6 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -378,6 +378,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr,
         error_report("%s userfault register: %s", __func__, strerror(errno));
         return -1;
     }
+    if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
+        error_report("%s userfault: Region doesn't support COPY", __func__);
+        return -1;
+    }
 
     return 0;
 }
-- 
2.9.3

Re: [Qemu-devel] [PATCH v3 16/16] postcopy: Add extra check for COPY function

[Laurent Vivier]

On 24/02/2017 19:28, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> As an extra sanity check, make sure the region we're registering
> can perform UFFDIO_COPY;  the COPY will fail later but this
> gives a cleaner failure.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  migration/postcopy-ram.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 102fb61..effbeb6 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -378,6 +378,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr,
>          error_report("%s userfault register: %s", __func__, strerror(errno));
>          return -1;
>      }
> +    if (!(reg_struct.ioctls & ((__u64)1 << _UFFDIO_COPY))) {
> +        error_report("%s userfault: Region doesn't support COPY", __func__);
> +        return -1;
> +    }
>  
>      return 0;
>  }
> 
Reviewed-by: Laurent Vivier <lvivier@redhat.com>