From: Sean Christopherson <seanjc@google.com>
To: David Matlack <dmatlack@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Ben Gardon <bgardon@google.com>,
Junaid Shahid <junaids@google.com>
Subject: Re: [PATCH v2] KVM: x86/mmu: Rename slot_handle_leaf to slot_handle_level_4k
Date: Thu, 21 Oct 2021 16:53:52 +0000 [thread overview]
Message-ID: <YXGbIHAJSPgYh34g@google.com> (raw)
In-Reply-To: <20211019162223.3935109-1-dmatlack@google.com>
On Tue, Oct 19, 2021, David Matlack wrote:
> slot_handle_leaf is a misnomer because it only operates on 4K SPTEs
> whereas "leaf" is used to describe any valid terminal SPTE (4K or
> large page). Rename slot_handle_leaf to slot_handle_level_4k to
> avoid confusion.
>
> Making this change makes it more obvious there is a benign discrepency
> between the legacy MMU and the TDP MMU when it comes to dirty logging.
> The legacy MMU only iterates through 4K SPTEs when zapping for
> collapsing and when clearing D-bits. The TDP MMU, on the other hand,
> iterates through SPTEs on all levels.
>
> The TDP MMU behavior of zapping SPTEs at all levels is technically
> overkill for its current dirty logging implementation, which always
> demotes to 4k SPTES, but both the TDP MMU and legacy MMU zap if and only
> if the SPTE can be replaced by a larger page, i.e. will not spuriously
> zap 2m (or larger) SPTEs. Opportunistically add comments to explain this
> discrepency in the code.
>
> Signed-off-by: David Matlack <dmatlack@google.com>
> ---
Reviewed-by: Sean Christopherson <seanjc@google.com>
prev parent reply other threads:[~2021-10-21 16:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 16:22 [PATCH v2] KVM: x86/mmu: Rename slot_handle_leaf to slot_handle_level_4k David Matlack
2021-10-19 23:38 ` Ben Gardon
2021-10-21 16:53 ` Sean Christopherson [this message]
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