From: Mingwei Zhang <mizhang@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
David Hildenbrand <david@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
David Matlack <dmatlack@google.com>,
Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH v3 14/28] KVM: x86/mmu: Skip remote TLB flush when zapping all of TDP MMU
Date: Thu, 3 Mar 2022 18:50:58 +0000 [thread overview]
Message-ID: <YiEOEjJHqyJJLtFz@google.com> (raw)
In-Reply-To: <20220226001546.360188-15-seanjc@google.com>
On Sat, Feb 26, 2022, Sean Christopherson wrote:
> Don't flush the TLBs when zapping all TDP MMU pages, as the only time KVM
> uses the slow version of "zap everything" is when the VM is being
> destroyed or the owning mm has exited. In either case, KVM_RUN is
> unreachable for the VM, i.e. the guest TLB entries cannot be consumed.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Mingwei Zhang <mizhang@google.com>
> ---
> arch/x86/kvm/mmu/tdp_mmu.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c231b60e1726..87706e9cc6f3 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -874,14 +874,15 @@ bool __kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, int as_id, gfn_t start,
>
> void kvm_tdp_mmu_zap_all(struct kvm *kvm)
> {
> - bool flush = false;
> int i;
>
> + /*
> + * A TLB flush is unnecessary, KVM zaps everything if and only the VM
> + * is being destroyed or the userspace VMM has exited. In both cases,
> + * KVM_RUN is unreachable, i.e. no vCPUs will ever service the request.
> + */
> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> - flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, 0, -1ull, flush);
> -
> - if (flush)
> - kvm_flush_remote_tlbs(kvm);
> + (void)kvm_tdp_mmu_zap_gfn_range(kvm, i, 0, -1ull, false);
> }
>
> /*
> --
> 2.35.1.574.g5d30c73bfb-goog
>
next prev parent reply other threads:[~2022-03-03 18:51 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-26 0:15 [PATCH v3 00/28] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 01/28] KVM: x86/mmu: Use common iterator for walking invalid TDP MMU roots Sean Christopherson
2022-03-02 19:08 ` Mingwei Zhang
2022-03-02 19:51 ` Sean Christopherson
2022-03-03 0:57 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 02/28] KVM: x86/mmu: Check for present SPTE when clearing dirty bit in TDP MMU Sean Christopherson
2022-03-02 19:50 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 03/28] KVM: x86/mmu: Fix wrong/misleading comments in TDP MMU fast zap Sean Christopherson
2022-02-28 23:15 ` Ben Gardon
2022-02-26 0:15 ` [PATCH v3 04/28] KVM: x86/mmu: Formalize TDP MMU's (unintended?) deferred TLB flush logic Sean Christopherson
2022-03-02 23:59 ` Mingwei Zhang
2022-03-03 0:12 ` Sean Christopherson
2022-03-03 1:20 ` Mingwei Zhang
2022-03-03 1:41 ` Sean Christopherson
2022-03-03 4:50 ` Mingwei Zhang
2022-03-03 16:45 ` Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 05/28] KVM: x86/mmu: Document that zapping invalidated roots doesn't need to flush Sean Christopherson
2022-02-28 23:17 ` Ben Gardon
2022-02-26 0:15 ` [PATCH v3 06/28] KVM: x86/mmu: Require mmu_lock be held for write in unyielding root iter Sean Christopherson
2022-02-28 23:26 ` Ben Gardon
2022-02-26 0:15 ` [PATCH v3 07/28] KVM: x86/mmu: Check for !leaf=>leaf, not PFN change, in TDP MMU SP removal Sean Christopherson
2022-03-01 0:11 ` Ben Gardon
2022-03-03 18:02 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 08/28] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte Sean Christopherson
2022-03-03 18:08 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 09/28] KVM: x86/mmu: Drop RCU after processing each root in MMU notifier hooks Sean Christopherson
2022-03-03 18:24 ` Mingwei Zhang
2022-03-03 18:32 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 10/28] KVM: x86/mmu: Add helpers to read/write TDP MMU SPTEs and document RCU Sean Christopherson
2022-03-03 18:34 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 11/28] KVM: x86/mmu: WARN if old _or_ new SPTE is REMOVED in non-atomic path Sean Christopherson
2022-03-03 18:37 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 12/28] KVM: x86/mmu: Refactor low-level TDP MMU set SPTE helper to take raw vals Sean Christopherson
2022-03-03 18:47 ` Mingwei Zhang
2022-02-26 0:15 ` [PATCH v3 13/28] KVM: x86/mmu: Zap only the target TDP MMU shadow page in NX recovery Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 14/28] KVM: x86/mmu: Skip remote TLB flush when zapping all of TDP MMU Sean Christopherson
2022-03-01 0:19 ` Ben Gardon
2022-03-03 18:50 ` Mingwei Zhang [this message]
2022-02-26 0:15 ` [PATCH v3 15/28] KVM: x86/mmu: Add dedicated helper to zap TDP MMU root shadow page Sean Christopherson
2022-03-01 0:32 ` Ben Gardon
2022-03-03 21:19 ` Mingwei Zhang
2022-03-03 21:24 ` Mingwei Zhang
2022-03-03 23:06 ` Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 16/28] KVM: x86/mmu: Require mmu_lock be held for write to zap TDP MMU range Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 17/28] KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range() Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 18/28] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 19/28] KVM: x86/mmu: Defer TLB flush to caller when freeing TDP MMU shadow pages Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 20/28] KVM: x86/mmu: Allow yielding when zapping GFNs for defunct TDP MMU root Sean Christopherson
2022-03-01 18:21 ` Paolo Bonzini
2022-03-01 19:43 ` Sean Christopherson
2022-03-01 20:12 ` Paolo Bonzini
2022-03-02 2:13 ` Sean Christopherson
2022-03-02 14:54 ` Paolo Bonzini
2022-03-02 17:43 ` Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 21/28] KVM: x86/mmu: Zap roots in two passes to avoid inducing RCU stalls Sean Christopherson
2022-03-01 0:43 ` Ben Gardon
2022-02-26 0:15 ` [PATCH v3 22/28] KVM: x86/mmu: Zap defunct roots via asynchronous worker Sean Christopherson
2022-03-01 17:57 ` Ben Gardon
2022-03-02 17:25 ` Paolo Bonzini
2022-03-02 17:35 ` Sean Christopherson
2022-03-02 18:33 ` David Matlack
2022-03-02 18:36 ` Paolo Bonzini
2022-03-02 18:01 ` Sean Christopherson
2022-03-02 18:20 ` Paolo Bonzini
2022-03-02 19:33 ` Sean Christopherson
2022-03-02 20:14 ` Paolo Bonzini
2022-03-02 20:47 ` Sean Christopherson
2022-03-02 21:22 ` Paolo Bonzini
2022-03-02 22:25 ` Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 23/28] KVM: x86/mmu: Check for a REMOVED leaf SPTE before making the SPTE Sean Christopherson
2022-03-01 18:06 ` Ben Gardon
2022-02-26 0:15 ` [PATCH v3 24/28] KVM: x86/mmu: WARN on any attempt to atomically update REMOVED SPTE Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 25/28] KVM: selftests: Move raw KVM_SET_USER_MEMORY_REGION helper to utils Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 26/28] KVM: selftests: Split out helper to allocate guest mem via memfd Sean Christopherson
2022-02-28 23:36 ` David Woodhouse
2022-03-02 18:36 ` Paolo Bonzini
2022-03-02 21:55 ` David Woodhouse
2022-02-26 0:15 ` [PATCH v3 27/28] KVM: selftests: Define cpu_relax() helpers for s390 and x86 Sean Christopherson
2022-02-26 0:15 ` [PATCH v3 28/28] KVM: selftests: Add test to populate a VM with the max possible guest mem Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YiEOEjJHqyJJLtFz@google.com \
--to=mizhang@google.com \
--cc=bgardon@google.com \
--cc=borntraeger@linux.ibm.com \
--cc=david@redhat.com \
--cc=dmatlack@google.com \
--cc=frankja@linux.ibm.com \
--cc=imbrenda@linux.ibm.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).