From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: 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,
Hou Wenlong <houwenlong93@linux.alibaba.com>,
Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH 27/28] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched
Date: Tue, 30 Nov 2021 15:45:00 +0000 [thread overview]
Message-ID: <YaZG/NopJ7YaVUjD@google.com> (raw)
In-Reply-To: <df9d430c-2065-804b-2343-d4bcdb7b2464@redhat.com>
On Tue, Nov 30, 2021, Paolo Bonzini wrote:
> On 11/20/21 05:50, Sean Christopherson wrote:
> > if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
> > - rcu_read_unlock();
> > -
> > if (flush)
> > kvm_flush_remote_tlbs(kvm);
> > + rcu_read_unlock();
> > +
>
> Couldn't this sleep in kvm_make_all_cpus_request, whilst in an RCU read-side
> critical section?
No. And if kvm_make_all_cpus_request() can sleep, the TDP MMU is completely hosed
as tdp_mmu_zap_spte_atomic() and handle_removed_tdp_mmu_page() currently call
kvm_flush_remote_tlbs_with_range() while under RCU protection.
kvm_make_all_cpus_request_except() disables preemption via get_cpu(), and
smp_call_function() doubles down on disabling preemption as the inner helpers
require preemption to be disabled, so anything below them should complain if
there's a might_sleep(). hv_remote_flush_tlb_with_range() takes a spinlock, so
nothing in there should be sleeping either.
next prev parent reply other threads:[~2021-11-30 15:45 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-20 4:50 [PATCH 00/28] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing Sean Christopherson
2021-11-20 4:50 ` [PATCH 01/28] KVM: x86/mmu: Use yield-safe TDP MMU root iter in MMU notifier unmapping Sean Christopherson
2021-11-22 19:48 ` Ben Gardon
2021-11-30 8:03 ` Paolo Bonzini
2021-11-20 4:50 ` [PATCH 02/28] KVM: x86/mmu: Skip tlb flush if it has been done in zap_gfn_range() Sean Christopherson
2021-11-20 4:50 ` [PATCH 03/28] KVM: x86/mmu: Remove spurious TLB flushes in TDP MMU zap collapsible path Sean Christopherson
2021-11-20 4:50 ` [PATCH 04/28] KVM: x86/mmu: Retry page fault if root is invalidated by memslot update Sean Christopherson
2021-11-22 19:54 ` Ben Gardon
2021-12-01 20:49 ` Paolo Bonzini
2021-12-08 19:17 ` Sean Christopherson
2021-11-20 4:50 ` [PATCH 05/28] KVM: x86/mmu: Check for present SPTE when clearing dirty bit in TDP MMU Sean Christopherson
2021-11-22 19:57 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 06/28] KVM: x86/mmu: Formalize TDP MMU's (unintended?) deferred TLB flush logic Sean Christopherson
2021-11-20 4:50 ` [PATCH 07/28] KVM: x86/mmu: Document that zapping invalidated roots doesn't need to flush Sean Christopherson
2021-11-20 4:50 ` [PATCH 08/28] KVM: x86/mmu: Drop unused @kvm param from kvm_tdp_mmu_get_root() Sean Christopherson
2021-11-22 20:02 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 09/28] KVM: x86/mmu: Require mmu_lock be held for write in unyielding root iter Sean Christopherson
2021-11-22 20:10 ` Ben Gardon
2021-11-22 20:19 ` Sean Christopherson
2021-11-20 4:50 ` [PATCH 10/28] KVM: x86/mmu: Allow yielding when zapping GFNs for defunct TDP MMU root Sean Christopherson
2021-11-22 21:30 ` Ben Gardon
2021-11-22 22:40 ` Sean Christopherson
2021-11-22 23:03 ` Ben Gardon
2021-12-14 23:45 ` Sean Christopherson
2021-12-14 23:52 ` Sean Christopherson
2021-11-20 4:50 ` [PATCH 11/28] KVM: x86/mmu: Check for !leaf=>leaf, not PFN change, in TDP MMU SP removal Sean Christopherson
2021-11-20 4:50 ` [PATCH 12/28] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte Sean Christopherson
2021-11-22 21:45 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 13/28] KVM: x86/mmu: Drop RCU after processing each root in MMU notifier hooks Sean Christopherson
2021-11-22 21:47 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 14/28] KVM: x86/mmu: Add helpers to read/write TDP MMU SPTEs and document RCU Sean Christopherson
2021-11-22 21:55 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 15/28] KVM: x86/mmu: Take TDP MMU roots off list when invalidating all roots Sean Christopherson
2021-11-22 22:20 ` Ben Gardon
2021-11-22 23:08 ` Sean Christopherson
2021-11-23 0:03 ` Ben Gardon
2021-12-14 23:34 ` Sean Christopherson
2021-11-20 4:50 ` [PATCH 16/28] KVM: x86/mmu: WARN if old _or_ new SPTE is REMOVED in non-atomic path Sean Christopherson
2021-11-22 21:57 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 17/28] KVM: x86/mmu: Terminate yield-friendly walk if invalid root observed Sean Christopherson
2021-11-22 22:25 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 18/28] KVM: x86/mmu: Refactor low-level TDP MMU set SPTE helper to take raw vals Sean Christopherson
2021-11-22 22:29 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 19/28] KVM: x86/mmu: Zap only the target TDP MMU shadow page in NX recovery Sean Christopherson
2021-11-22 22:43 ` Ben Gardon
2021-11-23 1:16 ` Sean Christopherson
2021-11-23 19:35 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 20/28] KVM: x86/mmu: Use common TDP MMU zap helper for MMU notifier unmap hook Sean Christopherson
2021-11-22 22:49 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 21/28] KVM: x86/mmu: Add TDP MMU helper to zap a root Sean Christopherson
2021-11-22 22:54 ` Ben Gardon
2021-11-22 23:15 ` Sean Christopherson
2021-11-22 23:38 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 22/28] KVM: x86/mmu: Skip remote TLB flush when zapping all of TDP MMU Sean Christopherson
2021-11-22 23:00 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 23/28] KVM: x86/mmu: Use "zap root" path for "slow" zap of all TDP MMU SPTEs Sean Christopherson
2021-11-20 4:50 ` [PATCH 24/28] KVM: x86/mmu: Add dedicated helper to zap TDP MMU root shadow page Sean Christopherson
2021-11-23 1:04 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 25/28] KVM: x86/mmu: Require mmu_lock be held for write to zap TDP MMU range Sean Christopherson
2021-11-23 19:58 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 26/28] KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range() Sean Christopherson
2021-11-23 19:58 ` Ben Gardon
2021-11-20 4:50 ` [PATCH 27/28] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched Sean Christopherson
2021-11-23 19:58 ` Ben Gardon
2021-11-24 18:42 ` Sean Christopherson
2021-11-30 11:29 ` Paolo Bonzini
2021-11-30 15:45 ` Sean Christopherson [this message]
2021-11-30 16:16 ` Paolo Bonzini
2021-11-20 4:50 ` [PATCH 28/28] KVM: x86/mmu: Defer TLB flush to caller when freeing TDP MMU shadow pages Sean Christopherson
2021-11-23 20:12 ` Ben Gardon
2021-12-01 17:53 ` [PATCH 00/28] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing David Matlack
2021-12-02 2:03 ` Sean Christopherson
2021-12-03 0:16 ` David Matlack
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