linux-kernel - Re: [PATCH 1/2] KVM: x86: fix APIC page invalidation

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Date:   Wed, 6 Dec 2017 09:15:40 +0100
From:   Fabian Grünbichler <f.gruenbichler@...xmox.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>
Subject: Re: [PATCH 1/2] KVM: x86: fix APIC page invalidation

On Thu, Nov 30, 2017 at 07:05:45PM +0100, Radim Krčmář wrote:
> Implementation of the unpinned APIC page didn't update the VMCS address
> cache when invalidation was done through range mmu notifiers.
> This became a problem when the page notifier was removed.
> 
> Re-introduce the arch-specific helper and call it from ...range_start.
> 
> Fixes: 38b9917350cb ("kvm: vmx: Implement set_apic_access_page_addr")
> Fixes: 369ea8242c0f ("mm/rmap: update to new mmu_notifier semantic v2")
> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>

Tested-by: Fabian Grünbichler <f.gruenbichler@...xmox.com>

no further issues observed with this patch applied on top of 4.13 and
4.14 - thanks!

> ---
>  arch/x86/include/asm/kvm_host.h |  3 +++
>  arch/x86/kvm/x86.c              | 14 ++++++++++++++
>  virt/kvm/kvm_main.c             |  8 ++++++++
>  3 files changed, 25 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 977de5fb968b..c16c3f924863 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1435,4 +1435,7 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
>  #define put_smstate(type, buf, offset, val)                      \
>  	*(type *)((buf) + (offset) - 0x7e00) = val
>  
> +void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
> +		unsigned long start, unsigned long end);
> +
>  #endif /* _ASM_X86_KVM_HOST_H */
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index eee8e7faf1af..a219974cdb89 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6778,6 +6778,20 @@ static void kvm_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
>  	kvm_x86_ops->tlb_flush(vcpu);
>  }
>  
> +void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
> +		unsigned long start, unsigned long end)
> +{
> +	unsigned long apic_address;
> +
> +	/*
> +	 * The physical address of apic access page is stored in the VMCS.
> +	 * Update it when it becomes invalid.
> +	 */
> +	apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
> +	if (start <= apic_address && apic_address < end)
> +		kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
> +}
> +
>  void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
>  {
>  	struct page *page = NULL;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index c01cff064ec5..b7f4689e373f 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -135,6 +135,11 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
>  static unsigned long long kvm_createvm_count;
>  static unsigned long long kvm_active_vms;
>  
> +__weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
> +		unsigned long start, unsigned long end)
> +{
> +}
> +
>  bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
>  {
>  	if (pfn_valid(pfn))
> @@ -360,6 +365,9 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
>  		kvm_flush_remote_tlbs(kvm);
>  
>  	spin_unlock(&kvm->mmu_lock);
> +
> +	kvm_arch_mmu_notifier_invalidate_range(kvm, start, end);
> +
>  	srcu_read_unlock(&kvm->srcu, idx);
>  }
>  
> -- 
> 2.14.2
> 
>