Messages in this thread | | | Subject | Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking | From | Jason Wang <> | Date | Thu, 5 Dec 2019 21:12:56 +0800 |
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On 2019/12/5 下午8:08, Peter Xu wrote: > On Thu, Dec 05, 2019 at 02:51:15PM +0800, Jason Wang wrote: >> On 2019/12/5 上午3:52, Peter Xu wrote: >>> On Wed, Dec 04, 2019 at 12:04:53PM +0100, Paolo Bonzini wrote: >>>> On 04/12/19 11:38, Jason Wang wrote: >>>>>> + entry = &ring->dirty_gfns[ring->dirty_index & (ring->size - 1)]; >>>>>> + entry->slot = slot; >>>>>> + entry->offset = offset; >>>>> Haven't gone through the whole series, sorry if it was a silly question >>>>> but I wonder things like this will suffer from similar issue on >>>>> virtually tagged archs as mentioned in [1]. >>>> There is no new infrastructure to track the dirty pages---it's just a >>>> different way to pass them to userspace. >>>> >>>>> Is this better to allocate the ring from userspace and set to KVM >>>>> instead? Then we can use copy_to/from_user() friends (a little bit slow >>>>> on recent CPUs). >>>> Yeah, I don't think that would be better than mmap. >>> Yeah I agree, because I didn't see how copy_to/from_user() helped to >>> do icache/dcache flushings... >> >> It looks to me one advantage is that exact the same VA is used by both >> userspace and kernel so there will be no alias. > Hmm.. but what if the page is mapped more than once in user? Thanks,
Then it's the responsibility of userspace program to do the flush I think.
Thanks
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