On 2/18/2025 5:19 PM, Alexey Kardashevskiy wrote:
>
>
> On 17/2/25 19:18, Chenyi Qiang wrote:
>> Introduce a new state_change() callback in MemoryAttributeManagerClass to
>> efficiently notify all registered RamDiscardListeners, including VFIO
>> listeners about the memory conversion events in guest_memfd. The
>> existing VFIO listener can dynamically DMA map/unmap the shared pages
>> based on conversion types:
>> - For conversions from shared to private, the VFIO system ensures the
>> discarding of shared mapping from the IOMMU.
>> - For conversions from private to shared, it triggers the population of
>> the shared mapping into the IOMMU.
>>
>> Additionally, there could be some special conversion requests:
>> - When a conversion request is made for a page already in the desired
>> state, the helper simply returns success.
>> - For requests involving a range partially in the desired state, only
>> the necessary segments are converted, ensuring the entire range
>> complies with the request efficiently.
>> - In scenarios where a conversion request is declined by other systems,
>> such as a failure from VFIO during notify_populate(), the helper will
>> roll back the request, maintaining consistency.
>>
>> Opportunistically introduce a helper to trigger the state_change()
>> callback of the class.
>>
>> Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
>> ---
>> Changes in v2:
>> - Do the alignment changes due to the rename to
>> MemoryAttributeManager
>> - Move the state_change() helper definition in this patch.
>> ---
>> include/system/memory-attribute-manager.h | 20 +++
>> system/memory-attribute-manager.c | 148 ++++++++++++++++++++++
>> 2 files changed, 168 insertions(+)
>>
>> diff --git a/include/system/memory-attribute-manager.h b/include/
>> system/memory-attribute-manager.h
>> index 72adc0028e..c3dab4e47b 100644
>> --- a/include/system/memory-attribute-manager.h
>> +++ b/include/system/memory-attribute-manager.h
>> @@ -34,8 +34,28 @@ struct MemoryAttributeManager {
>> struct MemoryAttributeManagerClass {
>> ObjectClass parent_class;
>> +
>> + int (*state_change)(MemoryAttributeManager *mgr, uint64_t offset,
>> uint64_t size,
>> + bool shared_to_private);
>> };
>> +static inline int
>> memory_attribute_manager_state_change(MemoryAttributeManager *mgr,
>> uint64_t offset,
>> + uint64_t
>> size, bool shared_to_private)
>> +{
>> + MemoryAttributeManagerClass *klass;
>> +
>> + if (mgr == NULL) {
>> + return 0;
>> + }
>> +
>> + klass = MEMORY_ATTRIBUTE_MANAGER_GET_CLASS(mgr);
>> + if (klass->state_change) {
>> + return klass->state_change(mgr, offset, size,
>> shared_to_private);
>> + }
>> +
>> + return 0;
>
>
> nit: MemoryAttributeManagerClass without this only callback defined
> should produce some error imho. Or assert.
Nice catch. Will return error if !klass->state_change.
>
>> +}
>> +
>> int memory_attribute_manager_realize(MemoryAttributeManager *mgr,
>> MemoryRegion *mr);
>> void memory_attribute_manager_unrealize(MemoryAttributeManager *mgr);
[..]
>> +
>> +static bool
>> memory_attribute_is_range_discarded(MemoryAttributeManager *mgr,
>> + uint64_t offset,
>> uint64_t size)
>> +{
>> + int block_size = memory_attribute_manager_get_block_size(mgr);
>> + const unsigned long first_bit = offset / block_size;
>> + const unsigned long last_bit = first_bit + (size / block_size) - 1;
>> + unsigned long found_bit;
>> +
>> + /* We fake a shorter bitmap to avoid searching too far. */
>
> Weird comment imho, why is it a "fake"? You check if all pages within
> [offset, offset+size) are discarded. You do not want to search beyond
> the end of this range anyway, right?
Yes. And I think the "fake" is aimed to describe the inconsistency with
the definition of find_next_bit(). find_next_bit() defines the second
argument as "The bitmap size in bits" but "last_bit + 1" is not the size
of shared_bitmap.
>
>> + found_bit = find_next_bit(mgr->shared_bitmap, last_bit + 1,
>> first_bit);
>> + return found_bit > last_bit;
>> +}
>> +
>> +static int memory_attribute_state_change(MemoryAttributeManager *mgr,
>> uint64_t offset,
>> + uint64_t size, bool
>> shared_to_private)
>
> Elsewhere it is just "to_private".
I'm OK to change it to "to_private" to keep alignment.
>
>> +{
>> + int block_size = memory_attribute_manager_get_block_size(mgr);
>> + int ret = 0;
>> +
>> + if (!memory_attribute_is_valid_range(mgr, offset, size)) {
>> + error_report("%s, invalid range: offset 0x%lx, size 0x%lx",
>> + __func__, offset, size);
>> + return -1;
>> + }
>> +
>> + if ((shared_to_private &&
>> memory_attribute_is_range_discarded(mgr, offset, size)) ||
>> + (!shared_to_private &&
>> memory_attribute_is_range_populated(mgr, offset, size))) {
>> + return 0;
>> + }
>> +
>> + if (shared_to_private) {
>> + memory_attribute_notify_discard(mgr, offset, size);
>> + } else {
>> + ret = memory_attribute_notify_populate(mgr, offset, size);
>> + }
>> +
>> + if (!ret) {
>> + unsigned long first_bit = offset / block_size;
>> + unsigned long nbits = size / block_size;
>> +
>> + g_assert((first_bit + nbits) <= mgr->bitmap_size);
>> +
>> + if (shared_to_private) {
>> + bitmap_clear(mgr->shared_bitmap, first_bit, nbits);
>> + } else {
>> + bitmap_set(mgr->shared_bitmap, first_bit, nbits);
>> + }
>> +
>> + return 0;
>
> Do not need this return. Thanks,
Removed. Thanks!
>
>> + }
>> +
>> + return ret;
>> +}
>> +
>> int memory_attribute_manager_realize(MemoryAttributeManager *mgr,
>> MemoryRegion *mr)
>> {
>> uint64_t bitmap_size;
>> @@ -281,8 +426,11 @@ static void
>> memory_attribute_manager_finalize(Object *obj)
>> static void memory_attribute_manager_class_init(ObjectClass *oc,
>> void *data)
>> {
>> + MemoryAttributeManagerClass *mamc =
>> MEMORY_ATTRIBUTE_MANAGER_CLASS(oc);
>> RamDiscardManagerClass *rdmc = RAM_DISCARD_MANAGER_CLASS(oc);
>> + mamc->state_change = memory_attribute_state_change;
>> +
>> rdmc->get_min_granularity =
>> memory_attribute_rdm_get_min_granularity;
>> rdmc->register_listener = memory_attribute_rdm_register_listener;
>> rdmc->unregister_listener =
>> memory_attribute_rdm_unregister_listener;
>
