On 2024/6/14 上午3:25, Christophe JAILLET wrote:
Le 13/06/2024 à 14:54, Bibo Mao a écrit :
Since dirty_bitmap pointer is allocated with function __vcalloc(),
there is __GFP_ZERO flag set in the implementation about this function
__vcalloc_noprof(). It is not necessary to clear dirty_bitmap buffer
with zero again.
Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
virt/kvm/kvm_main.c | 3 ---
1 file changed, 3 deletions(-)
Hi,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 14841acb8b95..c7d4a041dcfa 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1669,9 +1669,6 @@ static int kvm_prepare_memory_region(struct kvm
*kvm,
r = kvm_alloc_dirty_bitmap(new);
if (r)
return r;
-
- if (kvm_dirty_log_manual_protect_and_init_set(kvm))
- bitmap_set(new->dirty_bitmap, 0, new->npages);
unless I miss something obvious, this does not clear anything, but set
all bits to 1.
0 is not for "write 0" (i.e. clear), but for "start at offset 0".
So all bits are set to 1 in this case.
you are right, I had thought it is to write 0 :(
I do not know whether KVM_DIRTY_LOG_INITIALLY_SET should be enabled on
LoongArch. If it is set, write protection for second MMU will start one
by one in function kvm_arch_mmu_enable_log_dirty_pt_masked() when dirty
log is cleared if it is set, else write protection will start in
function kvm_arch_commit_memory_region() when flag of memslot is changed.
I do not see the obvious benefits between these two write protect
stages. Can anyone give me any hints?
Regards
Bibo Mao
CJ
}
}
base-commit: 83a7eefedc9b56fe7bfeff13b6c7356688ffa670
