linux-kernel - Re: [PATCH] KVM: x86: fix access memslots w/o hold srcu read lock

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Message-ID: <54544A45.1000505@gmail.com>
Date:	Sat, 01 Nov 2014 10:49:41 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	"Chen, Tiejun" <tiejun.chen@...el.com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
CC:	Gleb Natapov <gleb@...nel.org>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Takashi Iwai <tiwai@...e.de>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: fix access memslots w/o hold srcu read lock

Hi Paolo,
On 14/10/31 下午6:36, Paolo Bonzini wrote:
>
> On 31/10/2014 06:30, Chen, Tiejun wrote:
>> @@ -4442,6 +4442,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>>   {
>>          struct vcpu_vmx *vmx = to_vmx(vcpu);
>>          struct msr_data apic_base_msr;
>> +       int idx;
>>
>>          vmx->rmode.vm86_active = 0;
>>
>> @@ -4509,7 +4510,9 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>>                  vmcs_write32(TPR_THRESHOLD, 0);
>>          }
>>
>> +       idx = srcu_read_lock(&vcpu->kvm->srcu);
>>          kvm_vcpu_reload_apic_access_page(vcpu);
>> +       srcu_read_unlock(&vcpu->kvm->srcu, idx);
>>
>>          if (vmx_vm_has_apicv(vcpu->kvm))
>>                  memset(&vmx->pi_desc, 0, sizeof(struct pi_desc));
> Not enough; you can call vcpu_enter_guest -> kvm_apic_accept_events ->
> kvm_vcpu_reset -> vmx_vcpu_reset while under the SRCU lock.  The right
> place to add the lock is kvm_arch_vcpu_setup.

This is also not enough. I see the warning in the below path during the 
test:

kvm_arch_vcpu_ioctl_run
-> kvm_apic_accept_events
-> kvm_vcpu_reset

I just send out the version 3 and hope it can take care all the 
situations. ;-)

Regards,
Wanpeng Li

>
> Thanks,
>
> Paolo
> --
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