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[Qemu-devel] [PATCH 06/11] memory: Introduce memory listener hook log_cl
From: |
Peter Xu |
Subject: |
[Qemu-devel] [PATCH 06/11] memory: Introduce memory listener hook log_clear() |
Date: |
Wed, 8 May 2019 14:15:18 +0800 |
Introduce a new memory region listener hook log_clear() to allow the
listeners to hook onto the points where the dirty bitmap is cleared by
the bitmap users.
Previously log_sync() contains two operations:
- dirty bitmap collection, and,
- dirty bitmap clear on remote site.
Let's take KVM as example - log_sync() for KVM will first copy the
kernel dirty bitmap to userspace, and at the same time we'll clear the
dirty bitmap there along with re-protecting all the guest pages again.
We add this new log_clear() interface only to split the old log_sync()
into two separated procedures:
- use log_sync() to collect the collection only, and,
- use log_clear() to clear the remote dirty bitmap.
With the new interface, the memory listener users will still be able
to decide how to implement the log synchronization procedure, e.g.,
they can still only provide log_sync() method only and put all the two
procedures within log_sync() (that's how the old KVM works before
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT is introduced). However with this
new interface the memory listener users will start to have a chance to
postpone the log clear operation explicitly if the module supports.
That can really benefit users like KVM at least for host kernels that
support KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.
There are three places that can clear dirty bits in any one of the
dirty bitmap in the ram_list.dirty_memory[3] array:
cpu_physical_memory_snapshot_and_clear_dirty
cpu_physical_memory_test_and_clear_dirty
cpu_physical_memory_sync_dirty_bitmap
Currently we hook directly into each of the functions to notify about
the log_clear().
Signed-off-by: Peter Xu <address@hidden>
---
exec.c | 12 ++++++++++
include/exec/memory.h | 17 ++++++++++++++
include/exec/ram_addr.h | 3 +++
memory.c | 51 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 83 insertions(+)
diff --git a/exec.c b/exec.c
index 2615b4cfed..ab595e1e4b 100644
--- a/exec.c
+++ b/exec.c
@@ -1355,6 +1355,8 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t
start,
DirtyMemoryBlocks *blocks;
unsigned long end, page;
bool dirty = false;
+ RAMBlock *ramblock;
+ uint64_t mr_offset, mr_size;
if (length == 0) {
return false;
@@ -1366,6 +1368,10 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t
start,
rcu_read_lock();
blocks = atomic_rcu_read(&ram_list.dirty_memory[client]);
+ ramblock = qemu_get_ram_block(start);
+ /* Range sanity check on the ramblock */
+ assert(start >= ramblock->offset &&
+ start + length <= ramblock->offset + ramblock->used_length);
while (page < end) {
unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
@@ -1377,6 +1383,10 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t
start,
page += num;
}
+ mr_offset = (ram_addr_t)(page << TARGET_PAGE_BITS) - ramblock->offset;
+ mr_size = (end - page) << TARGET_PAGE_BITS;
+ memory_region_clear_dirty_bitmap(ramblock->mr, mr_offset, mr_size);
+
rcu_read_unlock();
if (dirty && tcg_enabled()) {
@@ -1432,6 +1442,8 @@ DirtyBitmapSnapshot
*cpu_physical_memory_snapshot_and_clear_dirty
tlb_reset_dirty_range_all(start, length);
}
+ memory_region_clear_dirty_bitmap(mr, addr, length);
+
return snap;
}
diff --git a/include/exec/memory.h b/include/exec/memory.h
index f29300c54d..d752b2a758 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -416,6 +416,7 @@ struct MemoryListener {
void (*log_stop)(MemoryListener *listener, MemoryRegionSection *section,
int old, int new);
void (*log_sync)(MemoryListener *listener, MemoryRegionSection *section);
+ void (*log_clear)(MemoryListener *listener, MemoryRegionSection *section);
void (*log_global_start)(MemoryListener *listener);
void (*log_global_stop)(MemoryListener *listener);
void (*eventfd_add)(MemoryListener *listener, MemoryRegionSection *section,
@@ -1269,6 +1270,22 @@ void memory_region_set_log(MemoryRegion *mr, bool log,
unsigned client);
void memory_region_set_dirty(MemoryRegion *mr, hwaddr addr,
hwaddr size);
+/**
+ * memory_region_clear_dirty_bitmap - clear dirty bitmap for memory range
+ *
+ * This function is called when the caller wants to clear the remote
+ * dirty bitmap of a memory range within the memory region. This can
+ * be used by e.g. KVM to manually clear dirty log when
+ * KVM_CAP_MANUAL_DIRTY_LOG_PROTECT is declared support by the host
+ * kernel.
+ *
+ * @mr: the memory region to clear the dirty log upon
+ * @start: start address offset within the memory region
+ * @len: length of the memory region to clear dirty bitmap
+ */
+void memory_region_clear_dirty_bitmap(MemoryRegion *mr, hwaddr start,
+ hwaddr len);
+
/**
* memory_region_snapshot_and_clear_dirty: Get a snapshot of the dirty
* bitmap and clear it.
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 69cc528c98..896324281a 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -461,6 +461,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
idx++;
}
}
+
+ /* TODO: split the huge bitmap into smaller chunks */
+ memory_region_clear_dirty_bitmap(rb->mr, start, length);
} else {
ram_addr_t offset = rb->offset;
diff --git a/memory.c b/memory.c
index be16beea76..b4e2c41ba0 100644
--- a/memory.c
+++ b/memory.c
@@ -2064,6 +2064,57 @@ static void memory_region_sync_dirty_bitmap(MemoryRegion
*mr)
}
}
+void memory_region_clear_dirty_bitmap(MemoryRegion *mr, hwaddr start,
+ hwaddr len)
+{
+ MemoryRegionSection mrs;
+ MemoryListener *listener;
+ AddressSpace *as;
+ FlatView *view;
+ FlatRange *fr;
+ hwaddr sec_start, sec_end, sec_size;
+
+ QTAILQ_FOREACH(listener, &memory_listeners, link) {
+ if (!listener->log_clear) {
+ continue;
+ }
+ as = listener->address_space;
+ view = address_space_get_flatview(as);
+ FOR_EACH_FLAT_RANGE(fr, view) {
+ if (!fr->dirty_log_mask || fr->mr != mr) {
+ /*
+ * Clear dirty bitmap operation only applies to those
+ * regions whose dirty logging is at least enabled
+ */
+ continue;
+ }
+
+ mrs = section_from_flat_range(fr, view);
+
+ sec_start = MAX(mrs.offset_within_region, start);
+ sec_end = mrs.offset_within_region + int128_get64(mrs.size);
+ sec_end = MIN(sec_end, start + len);
+
+ if (sec_start >= sec_end) {
+ /*
+ * If this memory region section has no intersection
+ * with the requested range, skip.
+ */
+ continue;
+ }
+
+ /* Valid case; shrink the section if needed */
+ mrs.offset_within_address_space +=
+ sec_start - mrs.offset_within_region;
+ mrs.offset_within_region = sec_start;
+ sec_size = sec_end - sec_start;
+ mrs.size = int128_make64(sec_size);
+ listener->log_clear(listener, &mrs);
+ }
+ flatview_unref(view);
+ }
+}
+
DirtyBitmapSnapshot *memory_region_snapshot_and_clear_dirty(MemoryRegion *mr,
hwaddr addr,
hwaddr size,
--
2.17.1
- [Qemu-devel] [PATCH 00/11] kvm/migration: support KVM_CLEAR_DIRTY_LOG, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 01/11] migration: No need to take rcu during sync_dirty_bitmap, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 02/11] memory: Remove memory_region_get_dirty(), Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 03/11] memory: Don't set migration bitmap when without migration, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 04/11] bitmap: Add bitmap_copy_with_{src|dst}_offset(), Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 05/11] memory: Pass mr into snapshot_and_clear_dirty, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 06/11] memory: Introduce memory listener hook log_clear(),
Peter Xu <=
- [Qemu-devel] [PATCH 07/11] kvm: Update comments for sync_dirty_bitmap, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 08/11] kvm: Persistent per kvmslot dirty bitmap, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 09/11] kvm: Introduce slots lock for memory listener, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 10/11] kvm: Support KVM_CLEAR_DIRTY_LOG, Peter Xu, 2019/05/08
- [Qemu-devel] [PATCH 11/11] migration: Split log_clear() into smaller chunks, Peter Xu, 2019/05/08
- Re: [Qemu-devel] [PATCH 00/11] kvm/migration: support KVM_CLEAR_DIRTY_LOG, Paolo Bonzini, 2019/05/08