From: Sean Christopherson <seanjc@google.com>
To: Ben Gardon <bgardon@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
Peter Shier <pshier@google.com>,
Junaid Shahid <junaids@google.com>,
Jim Mattson <jmattson@google.com>,
Yulei Zhang <yulei.kernel@gmail.com>,
Wanpeng Li <kernellwp@gmail.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Subject: Re: [PATCH v2 1/7] KVM: x86/mmu: Track if shadow MMU active
Date: Tue, 4 May 2021 19:55:16 +0000 [thread overview]
Message-ID: <YJGmpOzaFy9E0f5T@google.com> (raw)
In-Reply-To: <20210429211833.3361994-2-bgardon@google.com>
On Thu, Apr 29, 2021, Ben Gardon wrote:
> Add a field to each VM to track if the shadow / legacy MMU is actually
> in use. If the shadow MMU is not in use, then that knowledge opens the
> door to other optimizations which will be added in future patches.
>
> Signed-off-by: Ben Gardon <bgardon@google.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/mmu/mmu.c | 10 +++++++++-
> arch/x86/kvm/mmu/mmu_internal.h | 2 ++
> arch/x86/kvm/mmu/tdp_mmu.c | 6 ++++--
> arch/x86/kvm/mmu/tdp_mmu.h | 4 ++--
> 5 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index ad22d4839bcc..3900dcf2439e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1122,6 +1122,8 @@ struct kvm_arch {
> */
> spinlock_t tdp_mmu_pages_lock;
> #endif /* CONFIG_X86_64 */
> +
> + bool shadow_mmu_active;
I'm not a fan of the name, "shadow mmu" in KVM almost always means shadow paging
of some form, whereas this covers both shadow paging and legacy TDP support.
But, I think we we can avoid bikeshedding by simply eliminating this flag. More
in later patches.
> };
>
> struct kvm_vm_stat {
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 930ac8a7e7c9..3975272321d0 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3110,6 +3110,11 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> return ret;
> }
>
> +void activate_shadow_mmu(struct kvm *kvm)
> +{
> + kvm->arch.shadow_mmu_active = true;
> +}
> +
> static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
> struct list_head *invalid_list)
> {
> @@ -3280,6 +3285,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> }
> }
>
> + activate_shadow_mmu(vcpu->kvm);
> +
> write_lock(&vcpu->kvm->mmu_lock);
> r = make_mmu_pages_available(vcpu);
> if (r < 0)
> @@ -5467,7 +5474,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
> {
> struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
>
> - kvm_mmu_init_tdp_mmu(kvm);
> + if (!kvm_mmu_init_tdp_mmu(kvm))
> + activate_shadow_mmu(kvm);
Doesn't come into play yet, but I would strongly prefer to open code setting the
necessary flag instead of relying on the helper to never fail.
next prev parent reply other threads:[~2021-05-04 19:55 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 21:18 [PATCH v2 0/7] Lazily allocate memslot rmaps Ben Gardon
2021-04-29 21:18 ` [PATCH v2 1/7] KVM: x86/mmu: Track if shadow MMU active Ben Gardon
2021-05-03 13:42 ` Paolo Bonzini
2021-05-04 17:26 ` Ben Gardon
2021-05-04 20:18 ` Paolo Bonzini
2021-05-04 19:55 ` Sean Christopherson [this message]
2021-05-04 20:26 ` Paolo Bonzini
2021-05-04 20:36 ` Sean Christopherson
2021-04-29 21:18 ` [PATCH v2 2/7] KVM: x86/mmu: Skip rmap operations if shadow MMU inactive Ben Gardon
2021-04-29 21:18 ` [PATCH v2 3/7] KVM: x86/mmu: Deduplicate rmap freeing Ben Gardon
2021-04-29 21:18 ` [PATCH v2 4/7] KVM: x86/mmu: Factor out allocating memslot rmap Ben Gardon
2021-04-29 21:18 ` [PATCH v2 5/7] KVM: mmu: Refactor memslot copy Ben Gardon
2021-04-29 21:18 ` [PATCH v2 6/7] KVM: mmu: Add slots_arch_lock for memslot arch fields Ben Gardon
2021-05-03 13:29 ` Paolo Bonzini
2021-04-29 21:18 ` [PATCH v2 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps Ben Gardon
2021-05-03 13:42 ` Paolo Bonzini
2021-05-03 17:29 ` Ben Gardon
2021-05-04 20:13 ` Sean Christopherson
2021-05-04 20:19 ` Paolo Bonzini
2021-05-04 20:34 ` Sean Christopherson
2021-05-04 20:22 ` Paolo Bonzini
2021-05-03 13:44 ` [PATCH v2 0/7] " Paolo Bonzini
2021-05-03 17:31 ` Ben Gardon
2021-05-04 7:21 ` Paolo Bonzini
2021-05-04 17:28 ` Ben Gardon
2021-05-04 18:17 ` Sean Christopherson
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