From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 05/15] Coalesce userspace/kernel irqchip interrupt injection
 logic.
Date: Sun, 19 Apr 2009 11:52:07 +0300
Message-ID: <49EAE637.5000204@redhat.com>
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Cc: Gleb Natapov <gleb@redhat.com>, kvm@vger.kernel.org,
	joerg.roedel@amd.com, sheng@linux.intel.com,
	Dmitry Baryshkov <dbaryshkov@gmail.com>
To: Jan Kiszka <jan.kiszka@web.de>
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Jan Kiszka wrote:
>> -
>> -	if (!npt_enabled && event_injection)
>> -		kvm_mmu_unprotect_page_virt(&svm->vcpu, fault_address);
>> +	else {
>> +		if (svm->vcpu.arch.interrupt.pending ||
>> +				svm->vcpu.arch.exception.pending)
>> +			kvm_mmu_unprotect_page_virt(&svm->vcpu, fault_address);
>> +	}
>>     
>
> Without understanding yet why kvm_mmu_unprotect_page_virt is required
> here,

That is needed in case interrupt injection failed because the process of 
injecting the interrupt (usually pushing data on the stack) writes to a 
write-protected page table.

I guess we need nmi_pending here as well.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.