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From: | Zenghui Yu |
Subject: | Re: [PATCH] kvm: Take into account the unaligned section size when preparing bitmap |
Date: | Thu, 10 Dec 2020 11:31:22 +0800 |
User-agent: | Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 |
On 2020/12/10 10:53, zhukeqian wrote:
On 2020/12/10 10:08, Peter Xu wrote:Keqian, On Thu, Dec 10, 2020 at 09:46:06AM +0800, zhukeqian wrote:Hi, I see that if start or size is not PAGE aligned, it also clears areas which beyond caller's expectation, so do we also need to consider this?
Ah, I really don't anticipate this to happen but ... The question is what's the expectation of the caller if a non-PAGE aligned @start is given. Should we clear dirty state for the page which covers the unaligned @start? Or just skip it?
Could you elaborate? If start_delta != 0, kvm_log_clear_one_slot() should already go the slow path. Thanks,Hi Peter, start_delta /= psize; If start is not PAGE aligned, then start_delta is not PAGE aligned. so I think the above code will implicitly extend our start to be PAGE aligned. I suggest that we should shrink the start and (start + size) to be PAGE aligned at beginning of this function.
I don't object to do so (though haven't checked the code carefully). I also don't think there is much we can do given that the caller doesn't care about which *exact pages* to clear. Thanks, Zenghui
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