linux-kernel - Re: [PATCH v2 04/22] KVM: x86: introduce vcpu_gva_to

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Message-ID: <4E0B0BCA.5050103@cn.fujitsu.com>
Date:	Wed, 29 Jun 2011 19:26:02 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 04/22] KVM: x86: introduce vcpu_gva_to_gpa to cleanup
 the code

On 06/29/2011 07:09 PM, Avi Kivity wrote:
> On 06/29/2011 01:56 PM, Xiao Guangrong wrote:
>> On 06/29/2011 04:24 PM, Avi Kivity wrote:
>>
>> >>  +static int vcpu_gva_to_gpa(struct kvm_vcpu *vcpu, unsigned long gva,
>> >>  +               gpa_t *gpa, struct x86_exception *exception,
>> >>  +               bool write)
>> >>  +{
>> >>  +    u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
>> >>  +
>> >>  +    if (write)
>> >>  +        access |= PFERR_WRITE_MASK;
>> >
>> >  Needs fetch as well so NX/SMEP can work.
>> >
>>
>> This function is only used by read/write emulator, execute permission is
>> not needed for read/write, no?
> 
> It's not good to have a function which only implements the functionality partially.  It can later be misused.
> 
> You can pass the page-fault-error-code instead of the write parameter, I think it will be simpler.
> 

Actually, we will get the cache mmio info in this function, i think it is pure waste for other
access execpt mmio, what about change the function name to vcpu_gva_to_gpa_mmio?
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