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Message-ID: <ZB25pR7cv3mjnn4s@google.com>
Date: Fri, 24 Mar 2023 07:54:29 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Jun Miao <jun.miao@...el.com>
Cc: pbonzini@...hat.com, kvm@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: Fix comments that refer to the non-existent install_new_memslots()
On Thu, Feb 23, 2023, Jun Miao wrote:
> The function of install_new_memslots() was replaced by kvm_swap_active_memslots().
> In order to avoid confusion, fix the comments that refer the non-existent name of
> install_new_memslots which always be ignored.
>
> Fixes: a54d806688fe ("KVM: Keep memslots in tree-based structures instead of array-based ones")
> Signed-off-by: Jun Miao <jun.miao@...el.com>
Two nits, but I'll fix them up when applying. Thanks!
> ---
> Documentation/virt/kvm/locking.rst | 2 +-
> include/linux/kvm_host.h | 4 ++--
> virt/kvm/kvm_main.c | 10 +++++-----
> 3 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst
> index 14c4e9fa501d..6e03ad853c27 100644
> --- a/Documentation/virt/kvm/locking.rst
> +++ b/Documentation/virt/kvm/locking.rst
> @@ -21,7 +21,7 @@ The acquisition orders for mutexes are as follows:
> - kvm->mn_active_invalidate_count ensures that pairs of
> invalidate_range_start() and invalidate_range_end() callbacks
> use the same memslots array. kvm->slots_lock and kvm->slots_arch_lock
> - are taken on the waiting side in install_new_memslots, so MMU notifiers
> + are taken on the waiting side in kvm_swap_active_memslots(), so MMU notifiers
This isn't accurate, kvm_swap_active_memslots() isn't what actually acquires
those locks. I don't see any reason to be super precise, the key takeaway is
that modifying memslots takes the locks _and_ is the waiter. I'll tweak this to:
are taken on the waiting side when modifying memslots, so MMU notifiers
> @@ -1810,11 +1810,11 @@ static int kvm_set_memslot(struct kvm *kvm,
> int r;
>
> /*
> - * Released in kvm_swap_active_memslots.
> + * Released in kvm_swap_active_memslots().
> *
> * Must be held from before the current memslots are copied until
> * after the new memslots are installed with rcu_assign_pointer,
> - * then released before the synchronize srcu in kvm_swap_active_memslots.
> + * then released before the synchronize srcu in kvm_swap_active_memslots().
This block can be massaged slightly to avoid running past 80 chars:
* Must be held from before the current memslots are copied until after
* the new memslots are installed with rcu_assign_pointer, then
* released before the synchronize srcu in kvm_swap_active_memslots().
> *
> * When modifying memslots outside of the slots_lock, must be held
> * before reading the pointer to the current memslots until after all
> --
> 2.32.0
>
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