linux-kernel - Re: [PATCH v3 5/6] KVM: introduce gfn_to_hva_read/kvm_read_hva/kvm_read_hva

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Message-ID: <4FDFE2D6.1010706@linux.vnet.ibm.com>
Date:	Tue, 19 Jun 2012 10:24:22 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.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 v3 5/6] KVM: introduce gfn_to_hva_read/kvm_read_hva/kvm_read_hva_atomic

On 06/18/2012 06:16 PM, Avi Kivity wrote:

> On 06/12/2012 05:48 AM, Xiao Guangrong wrote:
>> This set of functions is only used to read data from host space, read is
>> a special case in the later patch
>>
>>
>> +/*
>> + * The hva returned by this function is only allowed to be read.
>> + * It should pair with kvm_read_hva() or kvm_read_hva_atomic().
>> + */
>> +static unsigned long gfn_to_hva_read(struct kvm *kvm, gfn_t gfn)
>> +{
>> +	return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL);
>> +}
>> +
>> +static int kvm_read_hva(void *data, void *hva, int len)
>> +{
>> +	return __copy_from_user(data, (void __user *)hva, len);
>> +
>> +}
>> +
>> +static int kvm_read_hva_atomic(void *data, void *hva, int len)
>> +{
>> +	return __copy_from_user_inatomic(data, (void __user *)hva, len);
>> +
>> +}
> 
> Why cast to __user?  Make it __user in the first place.
> 


Okay.

> Also these are just simple wrappers, why to them at all?


For gfn_to_hva_read(), they will call gfn_to_hva_many(...write = false)
in the later patch.

For kvm_read_hva() and kvm_read_hva_atomic(), they are pure wrappers,
i think its name is a good hint to let gfn_to_hva_read to pair with
kvm_read_hva()/kvm_read_hva_atomic().

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