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To:     Sean Christopherson <seanjc@google.com>,
        Ben Gardon <bgardon@google.com>
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        Peter Xu <peterx@redhat.com>, Peter Shier <pshier@google.com>,
        Yulei Zhang <yulei.kernel@gmail.com>,
        Wanpeng Li <kernellwp@gmail.com>,
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        Kai Huang <kai.huang@intel.com>,
        Keqian Zhu <zhukeqian1@huawei.com>,
        David Hildenbrand <david@redhat.com>
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From:   Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v4 4/7] KVM: mmu: Add slots_arch_lock for memslot arch
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Date:   Tue, 11 May 2021 21:29:19 +0200
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On 11/05/21 21:21, Sean Christopherson wrote:
>> +	/* Released in install_new_memslots. */
> 
> This needs a much more comprehensive comment, either here or above the declaration
> of slots_arch_lock.  I can't find anything that explicitly states the the lock
> must be held from the time the previous memslots are duplicated/copied until the
> new memslots are set.  Without that information, the rules/expecations are not
> clear.

Indeed, this needs basically a description of the races that can happen, 
as you explained them in the v1 review.

> Unfortunately I'm just whining at this point since I
> don't have a better idea 

Yeah, the synchronize_srcu call in install_new_memslots throws a wrench 
in most alternatives.

Paolo