From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>, Ben Gardon <bgardon@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Peter Xu <peterx@redhat.com>, Peter Shier <pshier@google.com>,
Yulei Zhang <yulei.kernel@gmail.com>,
Wanpeng Li <kernellwp@gmail.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Kai Huang <kai.huang@intel.com>,
Keqian Zhu <zhukeqian1@huawei.com>,
David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v4 4/7] KVM: mmu: Add slots_arch_lock for memslot arch fields
Date: Tue, 11 May 2021 21:29:19 +0200 [thread overview]
Message-ID: <ef473b52-0b71-a524-ed36-c2c1a9d0fb03@redhat.com> (raw)
In-Reply-To: <YJrZKkW9Cb9t+fU5@google.com>
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
next prev parent reply other threads:[~2021-05-11 19:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 17:16 [PATCH v4 0/7] Lazily allocate memslot rmaps Ben Gardon
2021-05-11 17:16 ` [PATCH v4 1/7] KVM: x86/mmu: Deduplicate rmap freeing Ben Gardon
2021-05-11 17:16 ` [PATCH v4 2/7] KVM: x86/mmu: Factor out allocating memslot rmap Ben Gardon
2021-05-11 17:56 ` Sean Christopherson
2021-05-11 18:17 ` Ben Gardon
2021-05-11 18:56 ` David Hildenbrand
2021-05-11 17:16 ` [PATCH v4 3/7] KVM: mmu: Refactor memslot copy Ben Gardon
2021-05-11 18:47 ` Sean Christopherson
2021-05-11 17:16 ` [PATCH v4 4/7] KVM: mmu: Add slots_arch_lock for memslot arch fields Ben Gardon
2021-05-11 18:55 ` Sean Christopherson
2021-05-11 19:21 ` Sean Christopherson
2021-05-11 19:29 ` Paolo Bonzini [this message]
2021-05-11 17:16 ` [PATCH v4 5/7] KVM: x86/mmu: Add a field to control memslot rmap allocation Ben Gardon
2021-05-11 17:16 ` [PATCH v4 6/7] KVM: x86/mmu: Skip rmap operations if rmaps not allocated Ben Gardon
2021-05-11 19:51 ` Sean Christopherson
2021-05-11 17:16 ` [PATCH v4 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps Ben Gardon
2021-05-11 18:57 ` Sean Christopherson
2021-05-11 20:03 ` Sean Christopherson
2021-05-11 20:04 ` Sean Christopherson
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