From: Binbin Wu <binbin.wu@linux.intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Michael Roth <michael.roth@amd.com>
Subject: Re: [PATCH 04/13] KVM: WARN if there are danging MMU invalidations at VM destruction
Date: Wed, 27 Sep 2023 11:16:22 +0800 [thread overview]
Message-ID: <7be47fe7-9587-dd1b-fac1-5c4d5c6e2ff6@linux.intel.com> (raw)
In-Reply-To: <20230921203331.3746712-5-seanjc@google.com>
On 9/22/2023 4:33 AM, Sean Christopherson wrote:
> Add an assertion that there are no in-progress MMU invalidations when a
> VM is being destroyed, with the exception of the scenario where KVM
> unregisters its MMU notifier between an .invalidate_range_start() call and
> the corresponding .invalidate_range_end().
>
> KVM can't detect unpaired calls from the mmu_notifier due to the above
> exception waiver, but the assertion can detect KVM bugs, e.g. such as the
> bug that *almost* escaped initial guest_memfd development.
>
> Link: https://lore.kernel.org/all/e397d30c-c6af-e68f-d18e-b4e3739c5389@linux.intel.com
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> virt/kvm/kvm_main.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 54480655bcce..277afeedd670 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1381,9 +1381,16 @@ static void kvm_destroy_vm(struct kvm *kvm)
> * No threads can be waiting in kvm_swap_active_memslots() as the
> * last reference on KVM has been dropped, but freeing
> * memslots would deadlock without this manual intervention.
> + *
> + * If the count isn't unbalanced, i.e. KVM did NOT unregister between
Nit: Readers can get it according to the code context, but is it better
to add
"MMU notifier" to tell what to "unregister" to make the comment easier to
understand?
> + * a start() and end(), then there shouldn't be any in-progress
> + * invalidations.
> */
> WARN_ON(rcuwait_active(&kvm->mn_memslots_update_rcuwait));
> - kvm->mn_active_invalidate_count = 0;
> + if (kvm->mn_active_invalidate_count)
> + kvm->mn_active_invalidate_count = 0;
> + else
> + WARN_ON(kvm->mmu_invalidate_in_progress);
> #else
> kvm_flush_shadow_all(kvm);
> #endif
next prev parent reply other threads:[~2023-09-27 4:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 20:33 [PATCH 00/13] KVM: guest_memfd fixes Sean Christopherson
2023-09-21 20:33 ` [PATCH 01/13] KVM: Assert that mmu_invalidate_in_progress *never* goes negative Sean Christopherson
2023-09-21 20:33 ` [PATCH 02/13] KVM: Actually truncate the inode when doing PUNCH_HOLE for guest_memfd Sean Christopherson
2023-09-21 20:33 ` [PATCH 03/13] KVM: WARN if *any* MMU invalidation sequence doesn't add a range Sean Christopherson
2023-09-21 20:33 ` [PATCH 04/13] KVM: WARN if there are danging MMU invalidations at VM destruction Sean Christopherson
2023-09-27 3:16 ` Binbin Wu [this message]
2023-09-28 18:11 ` Sean Christopherson
2023-09-21 20:33 ` [PATCH 05/13] KVM: Fix MMU invalidation bookkeeping in guest_memfd Sean Christopherson
2023-09-21 20:33 ` [PATCH 06/13] KVM: Disallow hugepages for incompatible gmem bindings, but let 'em succeed Sean Christopherson
2023-09-22 22:42 ` Michael Roth
2023-09-28 18:31 ` Sean Christopherson
2023-10-02 15:53 ` Michael Roth
2023-10-02 16:49 ` Sean Christopherson
2023-09-21 20:33 ` [PATCH 07/13] KVM: x86/mmu: Track PRIVATE impact on hugepage mappings for all memslots Sean Christopherson
2023-09-27 6:01 ` Binbin Wu
2023-09-27 14:25 ` Sean Christopherson
2023-09-21 20:33 ` [PATCH 08/13] KVM: x86/mmu: Zap shared-only memslots when private attribute changes Sean Christopherson
2023-09-21 20:33 ` [PATCH 09/13] KVM: Always add relevant ranges to invalidation set when changing attributes Sean Christopherson
2023-09-21 20:33 ` [PATCH 10/13] KVM: x86/mmu: Drop repeated add() of to-be-invalidated range Sean Christopherson
2023-09-21 20:33 ` [PATCH 11/13] KVM: selftests: Refactor private mem conversions to prep for punch_hole test Sean Christopherson
2023-09-21 20:33 ` [PATCH 12/13] KVM: selftests: Add a "pure" PUNCH_HOLE on guest_memfd testcase Sean Christopherson
2023-09-21 20:33 ` [PATCH 13/13] KVM: Rename guest_mem.c to guest_memfd.c Sean Christopherson
2023-09-29 2:22 ` [PATCH 00/13] KVM: guest_memfd fixes Sean Christopherson
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