On 08/11/2012 01:51 AM, Marcelo Tosatti wrote:
> On Tue, Aug 07, 2012 at 05:51:05PM +0800, Xiao Guangrong wrote:
>> We do too many things in hva_to_pfn, this patch reorganize the code,
>> let it be better readable
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
>> ---
>> virt/kvm/kvm_main.c | 159 +++++++++++++++++++++++++++++++--------------------
>> 1 files changed, 97 insertions(+), 62 deletions(-)
>>
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 26ffc87..dd01bcb 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -1043,83 +1043,118 @@ static inline int check_user_page_hwpoison(unsigned long addr)
>> return rc == -EHWPOISON;
>> }
>>
>> -static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
>> - bool write_fault, bool *writable)
>> +/*
>> + * The atomic path to get the writable pfn which will be stored in @pfn,
>> + * true indicates success, otherwise false is returned.
>> + */
>> +static bool hva_to_pfn_fast(unsigned long addr, bool atomic, bool *async,
>> + bool write_fault, bool *writable, pfn_t *pfn)
>> {
>> struct page *page[1];
>> - int npages = 0;
>> - pfn_t pfn;
>> + int npages;
>>
>> - /* we can do it either atomically or asynchronously, not both */
>> - BUG_ON(atomic && async);
>> + if (!(async || atomic))
>> + return false;
>>
>> - BUG_ON(!write_fault && !writable);
>> + npages = __get_user_pages_fast(addr, 1, 1, page);
>> + if (npages == 1) {
>> + *pfn = page_to_pfn(page[0]);
>>
>> - if (writable)
>> - *writable = true;
>> + if (writable)
>> + *writable = true;
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>>
>> - if (atomic || async)
>> - npages = __get_user_pages_fast(addr, 1, 1, page);
>> +/*
>> + * The slow path to get the pfn of the specified host virtual address,
>> + * 1 indicates success, -errno is returned if error is detected.
>> + */
>> +static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
>> + bool *writable, pfn_t *pfn)
>> +{
>> + struct page *page[1];
>> + int npages = 0;
>>
>> - if (unlikely(npages != 1) && !atomic) {
>> - might_sleep();
>> + might_sleep();
>>
>> - if (writable)
>> - *writable = write_fault;
>> -
>> - if (async) {
>> - down_read(¤t->mm->mmap_sem);
>> - npages = get_user_page_nowait(current, current->mm,
>> - addr, write_fault, page);
>> - up_read(¤t->mm->mmap_sem);
>> - } else
>> - 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];
>> -
>> - 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 (writable)
>> + *writable = write_fault;
>> +
>> + if (async) {
>> + down_read(¤t->mm->mmap_sem);
>> + npages = get_user_page_nowait(current, current->mm,
>> + addr, write_fault, page);
>> + up_read(¤t->mm->mmap_sem);
>> + } else
>> + npages = get_user_pages_fast(addr, 1, write_fault,
>> + page);
>> + if (npages != 1)
>> + return npages;
>
> * Returns number of pages pinned. This may be fewer than the number
> * requested. If nr_pages is 0 or negative, returns 0. If no pages
> * were pinned, returns -errno.
> */
> int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> struct page **pages)
>
>
> Current behaviour is
>
> if (atomic || async)
> npages = __get_user_pages_fast(addr, 1, 1, page);
>
> if (npages != 1)
> slow path retry;
>
> The changes above change this, don't they?
Marcelo,
Sorry, I do not know why you thought the logic was changed, in this patch,
the logic is:
/* return true if it is successful. */
if (hva_to_pfn_fast(addr, atomic, async, write_fault, writable, &pfn))
return pfn;
/* atomic can not go to slow path. */
if (atomic)
return KVM_PFN_ERR_FAULT;
/* get pfn by the slow path */
npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
if (npages == 1)
return pfn;
/* the error-handle path. */
......
Did i miss something?
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