Re: [PATCH] kvm: allow RO page when atomic && !write_fault

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 02/21/2011 05:47 PM, Gleb Natapov wrote:
> On Mon, Feb 21, 2011 at 11:47:36AM +0800, Lai Jiangshan wrote:
>>
>> Atomic-able hva_to_pfn() patches and allow-read-only-page patches
>> are merged almost the same time. But hva_to_pfn() does not handle
>> these two issues well together.
>>
>> When @atomic && !@write_fault && host-is-read-only-page-mapped
>> the code will return fault_page, actually, it will be better
>> if we return the pfn of the read-only-page.
>>
> This patch will conflict with not yet applied https://lkml.org/lkml/2011/2/1/94
> What it the status of that patch?

I will update/resend this patch after the patch you referred applied.

Thanks,
Lai

> 
>> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
>> ---
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 1fa0d29..f49cfc0 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -1060,31 +1060,27 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
>>  	BUG_ON(!write_fault && !writable);
>>  
>>  	if (writable)
>> -		*writable = true;
>> +		*writable = write_fault;
>>  
>>  	if (atomic || async)
>> -		npages = __get_user_pages_fast(addr, 1, 1, page);
>> +		npages = __get_user_pages_fast(addr, 1, write_fault, page);
>>  
>>  	if (unlikely(npages != 1) && !atomic) {
>>  		might_sleep();
>> -
>> -		if (writable)
>> -			*writable = write_fault;
>> -
>>  		npages = get_user_pages_fast(addr, 1, write_fault, page);
>> +	}
>>  
>> -		/* map read fault as writable if possible */
>> -		if (unlikely(!write_fault) && npages == 1) {
>> -			struct page *wpage[1];
>> +	/* map read fault as writable if possible */
>> +	if (unlikely(!write_fault) && npages == 1) {
>> +		struct page *wpage[1];
>>  
>> -			npages = __get_user_pages_fast(addr, 1, 1, wpage);
>> -			if (npages == 1) {
>> -				*writable = true;
>> -				put_page(page[0]);
>> -				page[0] = wpage[0];
>> -			}
>> -			npages = 1;
>> +		npages = __get_user_pages_fast(addr, 1, 1, wpage);
>> +		if (npages == 1) {
>> +			*writable = true;
>> +			put_page(page[0]);
>> +			page[0] = wpage[0];
>>  		}
>> +		npages = 1;
>>  	}
>>  
>>  	if (unlikely(npages != 1)) {
>> --
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> 
> --
> 			Gleb.
> --
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