linux-kernel - Re: [PATCH 08/10] KVM: introduce readonly_bad

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Date:	Fri, 20 Jul 2012 11:01:28 +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 08/10] KVM: introduce readonly_bad_hva

On 07/19/2012 06:16 PM, Avi Kivity wrote:
> On 07/17/2012 05:45 PM, Xiao Guangrong wrote:
>> In the later patch, it indicates failure when we try to get a writable
>> hva from the readonly slot
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
>> ---
>>  virt/kvm/kvm_main.c |   12 +++++++++++-
>>  1 files changed, 11 insertions(+), 1 deletions(-)
>>
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index b70f1a4..c056736 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -994,9 +994,19 @@ static inline unsigned long bad_hva(void)
>>  	return PAGE_OFFSET;
>>  }
>>
>> +static inline unsigned long readonly_bad_hva(void)
>> +{
>> +	return PAGE_OFFSET + PAGE_SIZE;
>> +}
>> +
>> +static int kvm_is_readonly_bad_hva(unsigned long addr)
>> +{
>> +	return addr == readonly_bad_hva();
>> +}
>> +
>>  int kvm_is_error_hva(unsigned long addr)
>>  {
>> -	return addr == bad_hva();
>> +	return addr == bad_hva() || kvm_is_readonly_bad_hva(addr);
>>  }
> 
> addr >= PAGE_OFFSET.  Or change it to use -E*.

I prefer to the first one, addr >= PAGE_OFFSET, all virtual addresses
between 0 and (~0ULL) are valid, Using PAGE_OFFSET is more readable.

[ is_error_pfn is suitable to use -err because the the range of physical
  address is always limited, for example,  0 ~ 64G on x86.]

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