vfio/iommu_type1: Add support for manual dirty log clear

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZUKK


CVE: NA

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In the past, we clear dirty log immediately after sync dirty
log to userspace. This may cause redundant dirty handling if
userspace handles dirty log iteratively:

After vfio clears dirty log, new dirty log starts to generate.
These new dirty log will be reported to userspace even if they
are generated before userspace handles the same dirty page.
That's to say, we should minimize the time gap of dirty log
clearing and dirty log handling.

This adds two user interfaces. Note that user should clear dirty
log before handle corresponding dirty pages.
1. GET_BITMAP_NOCLEAR: get dirty log without clear.
2. CLEAR_BITMAP: manually clear dirty log.

Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Reviewed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>