From: Sean Christopherson <seanjc@google.com>
To: Ben Gardon <bgardon@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Peter Shier <pshier@google.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH 4/4] KVM: x86/mmu: Factor out tdp_iter_return_to_root
Date: Fri, 12 Mar 2021 08:35:24 -0800 [thread overview]
Message-ID: <YEuYTF3mzzMCkz5c@google.com> (raw)
In-Reply-To: <20210311231658.1243953-5-bgardon@google.com>
On Thu, Mar 11, 2021, Ben Gardon wrote:
> In tdp_mmu_iter_cond_resched there is a call to tdp_iter_start which
> causes the iterator to continue its walk over the paging structure from
> the root. This is needed after a yield as paging structure could have
> been freed in the interim.
>
> The tdp_iter_start call is not very clear and something of a hack. It
> requires exposing tdp_iter fields not used elsewhere in tdp_mmu.c and
> the effect is not obvious from the function name. Factor a more aptly
> named function out of tdp_iter_start and call it from
> tdp_mmu_iter_cond_resched and tdp_iter_start.
What about calling it tdp_iter_restart()? Or tdp_iter_resume()? Or something
like tdp_iter_restart_at_next() if we want it to give a hint that the next_last
thing is where it restarts.
I think I like tdp_iter_restart() the best. It'd be easy enough to add a
function comment clarifying from where it restarts, and IMO the resulting code
in tdp_mmu_iter_cond_resched() is the most intutive, e.g. it makes it very clear
that the walk is being restarted in some capacity after yielding.
next prev parent reply other threads:[~2021-03-12 16:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 23:16 [PATCH 0/4] Fix RCU warnings in TDP MMU Ben Gardon
2021-03-11 23:16 ` [PATCH 1/4] KVM: x86/mmu: Fix RCU usage in handle_removed_tdp_mmu_page Ben Gardon
2021-03-12 15:37 ` Sean Christopherson
2021-03-12 15:43 ` Paolo Bonzini
2021-03-15 17:08 ` Ben Gardon
2021-03-11 23:16 ` [PATCH 2/4] KVM: x86/mmu: Fix RCU usage for tdp_iter_root_pt Ben Gardon
2021-03-12 16:22 ` Sean Christopherson
2021-03-15 17:13 ` Ben Gardon
2021-03-11 23:16 ` [PATCH 3/4] KVM: x86/mmu: Fix RCU usage when atomically zapping SPTEs Ben Gardon
2021-03-12 16:24 ` Sean Christopherson
2021-03-11 23:16 ` [PATCH 4/4] KVM: x86/mmu: Factor out tdp_iter_return_to_root Ben Gardon
2021-03-12 16:35 ` Sean Christopherson [this message]
2021-03-12 17:00 ` Paolo Bonzini
2021-03-12 17:01 ` [PATCH 0/4] Fix RCU warnings in TDP MMU Paolo Bonzini
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