The current error handling is simple with the following assumption:
- QEMU will quit instead of resuming the guest if kvm_convert_memory()
fails, thus no need to do rollback.
- The convert range is required to be in the desired state. It is not
allowed to handle the mixture case.
- The conversion from shared to private is a non-failure operation.
This is sufficient for now as complext error handling is not required.
For future extension, add some potential error handling.
- For private to shared conversion, do the rollback operation if
ram_block_attribute_notify_to_populated() fails.
- For shared to private conversion, still assert it as a non-failure
operation for now. It could be an easy fail path with in-place
conversion, which will likely have to retry the conversion until it
works in the future.
- For mixture case, process individual blocks for ease of rollback.
Signed-off-by: Chenyi Qiang <chenyi.qi...@intel.com>
---
system/ram-block-attribute.c | 116 +++++++++++++++++++++++++++--------
1 file changed, 90 insertions(+), 26 deletions(-)
diff --git a/system/ram-block-attribute.c b/system/ram-block-attribute.c
index 387501b569..0af3396aa4 100644
--- a/system/ram-block-attribute.c
+++ b/system/ram-block-attribute.c
@@ -289,7 +289,12 @@ static int
ram_block_attribute_notify_to_discard(RamBlockAttribute *attr,
}
ret = rdl->notify_discard(rdl, &tmp);
if (ret) {
- break;
+ /*
+ * The current to_private listeners (VFIO dma_unmap and
+ * KVM set_attribute_private) are non-failing operations.
+ * TODO: add rollback operations if it is allowed to fail.
+ */
+ g_assert(ret);
}
}
@@ -300,7 +305,7 @@ static int
ram_block_attribute_notify_to_populated(RamBlockAttribute *attr,
uint64_t offset, uint64_t size)
{
- RamDiscardListener *rdl;
+ RamDiscardListener *rdl, *rdl2;
int ret = 0;
QLIST_FOREACH(rdl, &attr->rdl_list, next) {
@@ -315,6 +320,20 @@ ram_block_attribute_notify_to_populated(RamBlockAttribute
*attr,
}
}
+ if (ret) {
+ /* Notify all already-notified listeners. */
+ QLIST_FOREACH(rdl2, &attr->rdl_list, next) {
+ MemoryRegionSection tmp = *rdl2->section;
+
+ if (rdl == rdl2) {
+ break;
+ }
+ if (!memory_region_section_intersect_range(&tmp, offset, size)) {
+ continue;
+ }
+ rdl2->notify_discard(rdl2, &tmp);
+ }
+ }
return ret;
}
@@ -353,6 +372,9 @@ int ram_block_attribute_state_change(RamBlockAttribute
*attr, uint64_t offset,
const int block_size = ram_block_attribute_get_block_size(attr);
const unsigned long first_bit = offset / block_size;
const unsigned long nbits = size / block_size;
+ const uint64_t end = offset + size;
+ unsigned long bit;
+ uint64_t cur;
int ret = 0;
if (!ram_block_attribute_is_valid_range(attr, offset, size)) {
@@ -361,32 +383,74 @@ int ram_block_attribute_state_change(RamBlockAttribute
*attr, uint64_t offset,
return -1;
}
- /* Already discard/populated */
- if ((ram_block_attribute_is_range_discard(attr, offset, size) &&
- to_private) ||
- (ram_block_attribute_is_range_populated(attr, offset, size) &&
- !to_private)) {
- return 0;
- }
-
- /* Unexpected mixture */
- if ((!ram_block_attribute_is_range_populated(attr, offset, size) &&
- to_private) ||
- (!ram_block_attribute_is_range_discard(attr, offset, size) &&
- !to_private)) {
- error_report("%s, the range is not all in the desired state: "
- "(offset 0x%lx, size 0x%lx), %s",
- __func__, offset, size,
- to_private ? "private" : "shared");
- return -1;
- }
-
if (to_private) {
- bitmap_clear(attr->bitmap, first_bit, nbits);
- ret = ram_block_attribute_notify_to_discard(attr, offset, size);
+ if (ram_block_attribute_is_range_discard(attr, offset, size)) {
+ /* Already private */
+ } else if (!ram_block_attribute_is_range_populated(attr, offset,
+ size)) {
+ /* Unexpected mixture: process individual blocks */
+ for (cur = offset; cur < end; cur += block_size) {
+ bit = cur / block_size;
+ if (!test_bit(bit, attr->bitmap)) {
+ continue;
+ }
+ clear_bit(bit, attr->bitmap);
+ ram_block_attribute_notify_to_discard(attr, cur, block_size);
+ }
+ } else {
+ /* Completely shared */
+ bitmap_clear(attr->bitmap, first_bit, nbits);
+ ram_block_attribute_notify_to_discard(attr, offset, size);
+ }
} else {
- bitmap_set(attr->bitmap, first_bit, nbits);
- ret = ram_block_attribute_notify_to_populated(attr, offset, size);
+ if (ram_block_attribute_is_range_populated(attr, offset, size)) {
+ /* Already shared */
+ } else if (!ram_block_attribute_is_range_discard(attr, offset, size)) {
+ /* Unexpected mixture: process individual blocks */
+ unsigned long *modified_bitmap = bitmap_new(nbits);
+
+ for (cur = offset; cur < end; cur += block_size) {
+ bit = cur / block_size;
+ if (test_bit(bit, attr->bitmap)) {
+ continue;
+ }
+ set_bit(bit, attr->bitmap);
+ ret = ram_block_attribute_notify_to_populated(attr, cur,
+ block_size);
+ if (!ret) {
+ set_bit(bit - first_bit, modified_bitmap);
+ continue;
+ }
+ clear_bit(bit, attr->bitmap);
+ break;
+ }
+
+ if (ret) {
+ /*
+ * Very unexpected: something went wrong. Revert to the old
+ * state, marking only the blocks as private that we converted
+ * to shared.
+ */
+ for (cur = offset; cur < end; cur += block_size) {
+ bit = cur / block_size;
+ if (!test_bit(bit - first_bit, modified_bitmap)) {
+ continue;
+ }
+ assert(test_bit(bit, attr->bitmap));
+ clear_bit(bit, attr->bitmap);
+ ram_block_attribute_notify_to_discard(attr, cur,
+ block_size);
+ }
+ }
+ g_free(modified_bitmap);
+ } else {
+ /* Complete private */
+ bitmap_set(attr->bitmap, first_bit, nbits);
+ ret = ram_block_attribute_notify_to_populated(attr, offset, size);
+ if (ret) {
+ bitmap_clear(attr->bitmap, first_bit, nbits);
+ }
+ }
}
return ret;
--
2.43.5
