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[Qemu-devel] [RFC v2 5/6] memory: replace cpu_physical_memory_reset_dirt
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [RFC v2 5/6] memory: replace cpu_physical_memory_reset_dirty() with test-and-clear |
Date: |
Tue, 2 Dec 2014 11:23:18 +0000 |
The cpu_physical_memory_reset_dirty() function is sometimes used
together with cpu_physical_memory_get_dirty(). This is not atomic since
two separate accesses to the dirty memory bitmap are made.
Turn cpu_physical_memory_reset_dirty() into the atomic
cpu_physical_memory_test_and_clear_dirty().
The cpu_physical_memory_clear_dirty_range() function is no longer used
and can be dropped.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
cputlb.c | 4 ++--
exec.c | 23 +++++++++++++++++------
include/exec/ram_addr.h | 27 +++++++--------------------
memory.c | 11 ++++-------
4 files changed, 30 insertions(+), 35 deletions(-)
diff --git a/cputlb.c b/cputlb.c
index a55518a..3d5b9a7 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -125,8 +125,8 @@ void tlb_flush_page(CPUState *cpu, target_ulong addr)
can be detected */
void tlb_protect_code(ram_addr_t ram_addr)
{
- cpu_physical_memory_reset_dirty(ram_addr, TARGET_PAGE_SIZE,
- DIRTY_MEMORY_CODE);
+ cpu_physical_memory_test_and_clear_dirty(ram_addr, TARGET_PAGE_SIZE,
+ DIRTY_MEMORY_CODE);
}
/* update the TLB so that writes in physical page 'phys_addr' are no longer
diff --git a/exec.c b/exec.c
index 71ac104..72bdb2e 100644
--- a/exec.c
+++ b/exec.c
@@ -845,16 +845,27 @@ static void tlb_reset_dirty_range_all(ram_addr_t start,
ram_addr_t length)
}
/* Note: start and end must be within the same ram block. */
-void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t length,
- unsigned client)
+bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start,
+ ram_addr_t length,
+ unsigned client)
{
- if (length == 0)
- return;
- cpu_physical_memory_clear_dirty_range(start, length, client);
+ unsigned long end, page;
+ bool dirty;
- if (tcg_enabled()) {
+ if (length == 0) {
+ return false;
+ }
+
+ end = TARGET_PAGE_ALIGN(start + length) >> TARGET_PAGE_BITS;
+ page = start >> TARGET_PAGE_BITS;
+ dirty = bitmap_test_and_clear_atomic(ram_list.dirty_memory[client],
+ page, end - page);
+
+ if (dirty && tcg_enabled()) {
tlb_reset_dirty_range_all(start, length);
}
+
+ return dirty;
}
static void cpu_physical_memory_set_dirty_tracking(bool enable)
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 87a8b28..cdcbe9a 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -175,20 +175,9 @@ static inline void
cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
}
#endif /* not _WIN32 */
-static inline void cpu_physical_memory_clear_dirty_range(ram_addr_t start,
- ram_addr_t length,
- unsigned client)
-{
- unsigned long end, page;
-
- assert(client < DIRTY_MEMORY_NUM);
- end = TARGET_PAGE_ALIGN(start + length) >> TARGET_PAGE_BITS;
- page = start >> TARGET_PAGE_BITS;
- bitmap_clear(ram_list.dirty_memory[client], page, end - page);
-}
-
-void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t length,
- unsigned client);
+bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start,
+ ram_addr_t length,
+ unsigned client);
static inline
uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned long *dest,
@@ -217,12 +206,10 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(unsigned
long *dest,
}
} else {
for (addr = 0; addr < length; addr += TARGET_PAGE_SIZE) {
- if (cpu_physical_memory_get_dirty(start + addr,
- TARGET_PAGE_SIZE,
- DIRTY_MEMORY_MIGRATION)) {
- cpu_physical_memory_reset_dirty(start + addr,
- TARGET_PAGE_SIZE,
- DIRTY_MEMORY_MIGRATION);
+ if (cpu_physical_memory_test_and_clear_dirty(
+ start + addr,
+ TARGET_PAGE_SIZE,
+ DIRTY_MEMORY_MIGRATION)) {
long k = (start + addr) >> TARGET_PAGE_BITS;
if (!test_and_set_bit(k, dest)) {
num_dirty++;
diff --git a/memory.c b/memory.c
index 15cf9eb..4d7761e 100644
--- a/memory.c
+++ b/memory.c
@@ -1375,13 +1375,9 @@ void memory_region_set_dirty(MemoryRegion *mr, hwaddr
addr,
bool memory_region_test_and_clear_dirty(MemoryRegion *mr, hwaddr addr,
hwaddr size, unsigned client)
{
- bool ret;
assert(mr->terminates);
- ret = cpu_physical_memory_get_dirty(mr->ram_addr + addr, size, client);
- if (ret) {
- cpu_physical_memory_reset_dirty(mr->ram_addr + addr, size, client);
- }
- return ret;
+ return cpu_physical_memory_test_and_clear_dirty(mr->ram_addr + addr,
+ size, client);
}
@@ -1425,7 +1421,8 @@ void memory_region_reset_dirty(MemoryRegion *mr, hwaddr
addr,
hwaddr size, unsigned client)
{
assert(mr->terminates);
- cpu_physical_memory_reset_dirty(mr->ram_addr + addr, size, client);
+ cpu_physical_memory_test_and_clear_dirty(mr->ram_addr + addr, size,
+ client);
}
int memory_region_get_fd(MemoryRegion *mr)
--
2.1.0
- [Qemu-devel] [RFC v2 0/6] memory: make dirty_memory[] accesses atomic, Stefan Hajnoczi, 2014/12/02
- [Qemu-devel] [RFC v2 1/6] bitmap: add atomic set functions, Stefan Hajnoczi, 2014/12/02
- [Qemu-devel] [RFC v2 2/6] bitmap: add atomic test and clear, Stefan Hajnoczi, 2014/12/02
- [Qemu-devel] [RFC v2 3/6] memory: use atomic ops for setting dirty memory bits, Stefan Hajnoczi, 2014/12/02
- [Qemu-devel] [RFC v2 4/6] migration: move dirty bitmap sync to ram_addr.h, Stefan Hajnoczi, 2014/12/02
- [Qemu-devel] [RFC v2 5/6] memory: replace cpu_physical_memory_reset_dirty() with test-and-clear,
Stefan Hajnoczi <=
- [Qemu-devel] [RFC v2 6/6] memory: make cpu_physical_memory_sync_dirty_bitmap() fully atomic, Stefan Hajnoczi, 2014/12/02