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

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Date:   Wed, 6 Dec 2017 11:00:16 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     王金浦 <jinpuwang@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Fabian Grünbichler <f.gruenbichler@...xmox.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, kvm <kvm@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>
Subject: Re: [PATCH 1/2] KVM: x86: fix APIC page invalidation

On 06/12/2017 10:50, 王金浦 wrote:
> 2017-12-06 3:32 GMT+01:00 Wanpeng Li <kernellwp@...il.com>:
>> 2017-12-01 2:05 GMT+08:00 Radim Krčmář <rkrcmar@...hat.com>:
>>> 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>
> So the patch should be backport to v3.18+?

In practice the invalidate_page callback was enough because the APIC
page is allocated with alloc_page().  But it doesn't hurt.

Paolo

> Thanks,
> Jack
>>
>> Tested-by: Wanpeng Li <wanpeng.li@...mail.com>
>>
>> I observe the windows 2016 guest hang during boot on a heavy memory
>> overcommit host, and this commit fixes it.
>>
>> Regards,
>> Wanpeng Li
>>
>>> ---
>>>  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
>>>
>>> --
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