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

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Message-ID: <4E0B0800.6030609@redhat.com>
Date:	Wed, 29 Jun 2011 14:09:52 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.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 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.

-- 
error compiling committee.c: too many arguments to function

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