linux-kernel - Re: [PATCH v2] KVM: nVMX: Fix the NMI IDT-vectoring handling

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Message-ID: <20160922231240.GC25134@potion>
Date:   Fri, 23 Sep 2016 01:12:40 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Bandan Das <bsd@...hat.com>
Subject: Re: [PATCH v2] KVM: nVMX: Fix the NMI IDT-vectoring handling

2016-09-22 17:55+0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@...mail.com>
> 
> Run kvm-unit-tests/eventinj.flat in L1:
> 
> Sending NMI to self
> After NMI to self
> FAIL: NMI
> 
> This test scenario is to test whether VMM can handle NMI IDT-vectoring info correctly.
> 
> At the beginning, L2 writes LAPIC to send a self NMI, the EPT page tables on both L1 
> and L0 are empty so:
> 
> - The L2 accesses memory can generate EPT violation which can be intercepted by L0.
> 
>   The EPT violation vmexit occurred during delivery of this NMI, and the NMI info is 
>   recorded in vmcs02's IDT-vectoring info.
> 
> - L0 walks L1's EPT12 and L0 sees the mapping is invalid, it injects the EPT violation into L1.
> 
>   The vmcs02's IDT-vectoring info is reflected to vmcs12's IDT-vectoring info since 
>   it is a nested vmexit. 
>   
> - L1 receives the EPT violation, then fixes its EPT12.
> - L1 executes VMRESUME to resume L2 which generates vmexit and causes L1 exits to L0.
> - L0 emulates VMRESUME which is called from L1, then return to L2.
> 
>   L0 merges the requirement of vmcs12's IDT-vectoring info and injects it to L2 through 
>   vmcs02.
> 
> - The L2 re-executes the fault instruction and cause EPT violation again.
> - Since the L1's EPT12 is valid, L0 can fix its EPT02
> - L0 resume L2
> 	
>   The EPT violation vmexit occurred during delivery of this NMI again, and the NMI info 
>   is recorded in vmcs02's IDT-vectoring info. L0 should inject the NMI through vmentry 
>   event injection since it is caused by EPT02's EPT violation.
> 
> However, vmx_inject_nmi() refuses to inject NMI from IDT-vectoring info if vCPU is in 
> guest mode, this patch fix it by permitting to inject NMI from IDT-vectoring if it is 
> the L0's responsibility to inject NMI from IDT-vectoring info to L2.
> 
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Jan Kiszka <jan.kiszka@...mens.com>
> Cc: Bandan Das <bsd@...hat.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
> ---

Applied to kvm/queue, thanks.