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Message-ID: <YoZv8HmRc7tqQbuL@google.com>
Date: Thu, 19 May 2022 16:27:28 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Maxim Levitsky <mlevitsk@...hat.com>
Cc: kvm@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Zhenyu Wang <zhenyuw@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Tom Lendacky <thomas.lendacky@....com>,
Ingo Molnar <mingo@...hat.com>,
David Airlie <airlied@...ux.ie>,
Thomas Gleixner <tglx@...utronix.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
intel-gfx@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
Zhi Wang <zhi.a.wang@...el.com>,
Brijesh Singh <brijesh.singh@....com>,
"H. Peter Anvin" <hpa@...or.com>,
intel-gvt-dev@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org
Subject: Re: [RFC PATCH v3 04/19] KVM: x86: mmu: allow to enable write
tracking externally
On Wed, Apr 27, 2022, Maxim Levitsky wrote:
> This will be used to enable write tracking from nested AVIC code
> and can also be used to enable write tracking in GVT-g module
> when it actually uses it as opposed to always enabling it,
> when the module is compiled in the kernel.
Wrap at ~75.
> No functional change intended.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/include/asm/kvm_page_track.h | 1 +
> arch/x86/kvm/mmu.h | 8 +++++---
> arch/x86/kvm/mmu/mmu.c | 17 ++++++++++-------
> arch/x86/kvm/mmu/page_track.c | 10 ++++++++--
> 5 files changed, 25 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 636df87542555..fc7df778a3d71 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1254,7 +1254,7 @@ struct kvm_arch {
> * is used as one input when determining whether certain memslot
> * related allocations are necessary.
> */
The above comment needs to be rewritten.
> - bool shadow_root_allocated;
> + bool mmu_page_tracking_enabled;
> #if IS_ENABLED(CONFIG_HYPERV)
> hpa_t hv_root_tdp;
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> index eb186bc57f6a9..955a5ae07b10e 100644
> --- a/arch/x86/include/asm/kvm_page_track.h
> +++ b/arch/x86/include/asm/kvm_page_track.h
> @@ -50,6 +50,7 @@ int kvm_page_track_init(struct kvm *kvm);
> void kvm_page_track_cleanup(struct kvm *kvm);
>
> bool kvm_page_track_write_tracking_enabled(struct kvm *kvm);
> +int kvm_page_track_write_tracking_enable(struct kvm *kvm);
> int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot);
>
> void kvm_page_track_free_memslot(struct kvm_memory_slot *slot);
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index 671cfeccf04e9..44d15551f7156 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -269,7 +269,7 @@ int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
> int kvm_mmu_post_init_vm(struct kvm *kvm);
> void kvm_mmu_pre_destroy_vm(struct kvm *kvm);
>
> -static inline bool kvm_shadow_root_allocated(struct kvm *kvm)
> +static inline bool mmu_page_tracking_enabled(struct kvm *kvm)
> {
> /*
> * Read shadow_root_allocated before related pointers. Hence, threads
> @@ -277,9 +277,11 @@ static inline bool kvm_shadow_root_allocated(struct kvm *kvm)
> * see the pointers. Pairs with smp_store_release in
> * mmu_first_shadow_root_alloc.
> */
This comment also needs to be rewritten.
> - return smp_load_acquire(&kvm->arch.shadow_root_allocated);
> + return smp_load_acquire(&kvm->arch.mmu_page_tracking_enabled);
> }
...
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index 2e09d1b6249f3..8857d629036d7 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -21,10 +21,16 @@
>
> bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
This can be static, it's now used only by page_track.c.
> {
> - return IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) ||
> - !tdp_enabled || kvm_shadow_root_allocated(kvm);
> + return mmu_page_tracking_enabled(kvm);
> }
>
> +int kvm_page_track_write_tracking_enable(struct kvm *kvm)
This is too similar to the "enabled" version; "kvm_page_track_enable_write_tracking()"
would maintain namespacing and be less confusing.
Hmm, I'd probably vote to make this a "static inline" in kvm_page_track.h, and
rename mmu_enable_write_tracking() to kvm_mmu_enable_write_tracking and export.
Not a strong preference, just feels silly to export a one-liner.
> +{
> + return mmu_enable_write_tracking(kvm);
> +}
> +EXPORT_SYMBOL_GPL(kvm_page_track_write_tracking_enable);
> +
> +
> void kvm_page_track_free_memslot(struct kvm_memory_slot *slot)
> {
> int i;
> --
> 2.26.3
>
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