From: David Matlack <dmatlack@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Gardon <bgardon@google.com>,
Mingwei Zhang <mizhang@google.com>
Subject: Re: [PATCH v2 04/30] KVM: x86/mmu: Use common iterator for walking invalid TDP MMU roots
Date: Tue, 4 Jan 2022 22:13:11 +0000 [thread overview]
Message-ID: <YdTGd3Anx2jrACRx@google.com> (raw)
In-Reply-To: <20211223222318.1039223-5-seanjc@google.com>
On Thu, Dec 23, 2021 at 10:22:52PM +0000, Sean Christopherson wrote:
> Now that tdp_mmu_next_root() can process both valid and invalid roots,
> extend it to be able to process _only_ invalid roots, add yet another
> iterator macro for walking invalid roots, and use the new macro in
> kvm_tdp_mmu_zap_invalidated_roots().
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Nice cleanup, it's great to see next_invalidated_root() go.
Reviewed-by: David Matlack <dmatlack@google.com>
> ---
> arch/x86/kvm/mmu/tdp_mmu.c | 74 ++++++++++++++------------------------
> 1 file changed, 26 insertions(+), 48 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 577985fa001d..41e975841ea6 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -98,6 +98,12 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
> call_rcu(&root->rcu_head, tdp_mmu_free_sp_rcu_callback);
> }
>
> +enum tdp_mmu_roots_iter_type {
> + ALL_ROOTS = -1,
> + VALID_ROOTS = 0,
> + INVALID_ROOTS = 1,
> +};
> +
> /*
> * Returns the next root after @prev_root (or the first root if @prev_root is
> * NULL). A reference to the returned root is acquired, and the reference to
> @@ -110,10 +116,16 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root,
> */
> static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> struct kvm_mmu_page *prev_root,
> - bool shared, bool only_valid)
> + bool shared,
> + enum tdp_mmu_roots_iter_type type)
> {
> struct kvm_mmu_page *next_root;
>
> + kvm_lockdep_assert_mmu_lock_held(kvm, shared);
> +
> + /* Ensure correctness for the below comparison against role.invalid. */
> + BUILD_BUG_ON(!!VALID_ROOTS || !INVALID_ROOTS);
> +
> rcu_read_lock();
>
> if (prev_root)
> @@ -125,7 +137,7 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> typeof(*next_root), link);
>
> while (next_root) {
> - if ((!only_valid || !next_root->role.invalid) &&
> + if ((type == ALL_ROOTS || (type == !!next_root->role.invalid)) &&
> kvm_tdp_mmu_get_root(kvm, next_root))
> break;
>
> @@ -151,18 +163,21 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> * mode. In the unlikely event that this thread must free a root, the lock
> * will be temporarily dropped and reacquired in write mode.
> */
> -#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _only_valid)\
> - for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _only_valid); \
> +#define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _type) \
> + for (_root = tdp_mmu_next_root(_kvm, NULL, _shared, _type); \
> _root; \
> - _root = tdp_mmu_next_root(_kvm, _root, _shared, _only_valid)) \
> - if (kvm_mmu_page_as_id(_root) != _as_id) { \
> + _root = tdp_mmu_next_root(_kvm, _root, _shared, _type)) \
> + if (_as_id > 0 && kvm_mmu_page_as_id(_root) != _as_id) { \
> } else
>
> +#define for_each_invalid_tdp_mmu_root_yield_safe(_kvm, _root) \
> + __for_each_tdp_mmu_root_yield_safe(_kvm, _root, -1, true, INVALID_ROOTS)
> +
> #define for_each_valid_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
> - __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, true)
> + __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, VALID_ROOTS)
>
> #define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared) \
> - __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, false)
> + __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, ALL_ROOTS)
>
> #define for_each_tdp_mmu_root(_kvm, _root, _as_id) \
> list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \
> @@ -811,28 +826,6 @@ void kvm_tdp_mmu_zap_all(struct kvm *kvm)
> kvm_flush_remote_tlbs(kvm);
> }
>
> -static struct kvm_mmu_page *next_invalidated_root(struct kvm *kvm,
> - struct kvm_mmu_page *prev_root)
> -{
> - struct kvm_mmu_page *next_root;
> -
> - if (prev_root)
> - next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
> - &prev_root->link,
> - typeof(*prev_root), link);
> - else
> - next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots,
> - typeof(*next_root), link);
> -
> - while (next_root && !(next_root->role.invalid &&
> - refcount_read(&next_root->tdp_mmu_root_count)))
> - next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
> - &next_root->link,
> - typeof(*next_root), link);
> -
> - return next_root;
> -}
> -
> /*
> * Since kvm_tdp_mmu_zap_all_fast has acquired a reference to each
> * invalidated root, they will not be freed until this function drops the
> @@ -843,36 +836,21 @@ static struct kvm_mmu_page *next_invalidated_root(struct kvm *kvm,
> */
> void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
> {
> - struct kvm_mmu_page *next_root;
> struct kvm_mmu_page *root;
> bool flush = false;
>
> lockdep_assert_held_read(&kvm->mmu_lock);
>
> - rcu_read_lock();
> -
> - root = next_invalidated_root(kvm, NULL);
> -
> - while (root) {
> - next_root = next_invalidated_root(kvm, root);
> -
> - rcu_read_unlock();
> -
> + for_each_invalid_tdp_mmu_root_yield_safe(kvm, root) {
> flush = zap_gfn_range(kvm, root, 0, -1ull, true, flush, true);
>
> /*
> - * Put the reference acquired in
> - * kvm_tdp_mmu_invalidate_roots
> + * Put the reference acquired in kvm_tdp_mmu_invalidate_roots().
> + * Note, the iterator holds its own reference.
> */
> kvm_tdp_mmu_put_root(kvm, root, true);
> -
> - root = next_root;
> -
> - rcu_read_lock();
> }
>
> - rcu_read_unlock();
> -
> if (flush)
> kvm_flush_remote_tlbs(kvm);
> }
> --
> 2.34.1.448.ga2b2bfdf31-goog
>
next prev parent reply other threads:[~2022-01-04 22:13 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-23 22:22 [PATCH v2 00/30] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 01/30] KVM: x86/mmu: Use common TDP MMU zap helper for MMU notifier unmap hook Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 02/30] KVM: x86/mmu: Move "invalid" check out of kvm_tdp_mmu_get_root() Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 03/30] KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 04/30] KVM: x86/mmu: Use common iterator for walking invalid TDP MMU roots Sean Christopherson
2022-01-04 22:13 ` David Matlack [this message]
2021-12-23 22:22 ` [PATCH v2 05/30] KVM: x86/mmu: Check for present SPTE when clearing dirty bit in TDP MMU Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 06/30] KVM: x86/mmu: Fix wrong/misleading comments in TDP MMU fast zap Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 07/30] KVM: x86/mmu: Formalize TDP MMU's (unintended?) deferred TLB flush logic Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 08/30] KVM: x86/mmu: Document that zapping invalidated roots doesn't need to flush Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 09/30] KVM: x86/mmu: Drop unused @kvm param from kvm_tdp_mmu_get_root() Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 10/30] KVM: x86/mmu: Require mmu_lock be held for write in unyielding root iter Sean Christopherson
2021-12-23 22:22 ` [PATCH v2 11/30] KVM: x86/mmu: Check for !leaf=>leaf, not PFN change, in TDP MMU SP removal Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 12/30] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 13/30] KVM: x86/mmu: Drop RCU after processing each root in MMU notifier hooks Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 14/30] KVM: x86/mmu: Add helpers to read/write TDP MMU SPTEs and document RCU Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 15/30] KVM: x86/mmu: WARN if old _or_ new SPTE is REMOVED in non-atomic path Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 16/30] KVM: x86/mmu: Refactor low-level TDP MMU set SPTE helper to take raw vals Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 17/30] KVM: x86/mmu: Zap only the target TDP MMU shadow page in NX recovery Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 18/30] KVM: x86/mmu: Skip remote TLB flush when zapping all of TDP MMU Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 19/30] KVM: x86/mmu: Add dedicated helper to zap TDP MMU root shadow page Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 20/30] KVM: x86/mmu: Require mmu_lock be held for write to zap TDP MMU range Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 21/30] KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range() Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 22/30] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 23/30] KVM: x86/mmu: Defer TLB flush to caller when freeing TDP MMU shadow pages Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 24/30] KVM: x86/mmu: Allow yielding when zapping GFNs for defunct TDP MMU root Sean Christopherson
2022-01-05 1:25 ` David Matlack
2022-01-05 21:32 ` Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 25/30] KVM: x86/mmu: Zap roots in two passes to avoid inducing RCU stalls Sean Christopherson
2022-01-05 0:19 ` David Matlack
2022-01-05 16:33 ` Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 26/30] KVM: x86/mmu: Zap defunct roots via asynchronous worker Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 27/30] KVM: selftests: Move raw KVM_SET_USER_MEMORY_REGION helper to utils Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 28/30] KVM: selftests: Split out helper to allocate guest mem via memfd Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 29/30] KVM: selftests: Define cpu_relax() helpers for s390 and x86 Sean Christopherson
2021-12-23 22:23 ` [PATCH v2 30/30] KVM: selftests: Add test to populate a VM with the max possible guest mem Sean Christopherson
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