linux-kernel - Re: [PATCH v4 3/6] KVM: MMU: introduce kvm_clear_all_lpage

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Date:	Fri, 03 May 2013 13:57:38 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
CC:	mtosatti@...hat.com, gleb@...hat.com, avi.kivity@...il.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v4 3/6] KVM: MMU: introduce kvm_clear_all_lpage_info

On 05/03/2013 10:15 AM, Takuya Yoshikawa wrote:
> On Sat, 27 Apr 2013 11:13:19 +0800
> Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:
> 
>> This function is used to reset the large page info of all guest pages
>> which will be used in later patch
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
>> ---
>>  arch/x86/kvm/x86.c |   25 +++++++++++++++++++++++++
>>  arch/x86/kvm/x86.h |    2 ++
>>  2 files changed, 27 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 52b4e97..8e4494c 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -6951,6 +6951,31 @@ static void memslot_set_lpage_disallowed(struct kvm_memory_slot *slot,
>>  	}
>>  }
>>  
>> +static void clear_memslot_lpage_info(struct kvm_memory_slot *slot)
>> +{
>> +	int i;
>> +
>> +	for (i = 1; i < KVM_NR_PAGE_SIZES; ++i) {
>> +		int lpages;
>> +		int level = i + 1;
>> +
>> +		lpages = gfn_to_index(slot->base_gfn + slot->npages - 1,
>> +				      slot->base_gfn, level) + 1;
>> +
>> +		memset(slot->arch.lpage_info[i - 1], 0,
>> +		       sizeof(*slot->arch.lpage_info[i - 1]));
>> +		memslot_set_lpage_disallowed(slot, slot->npages, i, lpages);
> 
> This does something other than clearing.

Aha, this API *clears* the count set by kvm mmu. It is meaningful enough,
i think.



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