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KVM: reorganize hva_to_pfn 

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@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Xiao Guangrong 2012-08-21 11:00:22 +08:00 committed by Avi Kivity
parent 86ab8cffb4
commit 2fc843117d
1 changed files with 97 additions and 62 deletions
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159
virt/kvm/kvm_main.c
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@ -1041,83 +1041,118 @@ 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;
if (!(async || atomic))
return false;
npages = __get_user_pages_fast(addr, 1, 1, page);
if (npages == 1) {
*pfn = page_to_pfn(page[0]);
if (writable)
*writable = true;
return true;
}
return false;
}
/*
* 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;
pfn_t pfn;
might_sleep();
if (writable)
*writable = write_fault;
if (async) {
down_read(&current->mm->mmap_sem);
npages = get_user_page_nowait(current, current->mm,
addr, write_fault, page);
up_read(&current->mm->mmap_sem);
} else
npages = get_user_pages_fast(addr, 1, write_fault,
page);
if (npages != 1)
return npages;
/* map read fault as writable if possible */
if (unlikely(!write_fault)) {
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;
}
*pfn = page_to_pfn(page[0]);
return npages;
}
static pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
bool write_fault, bool *writable)
{
struct vm_area_struct *vma;
pfn_t pfn = 0;
int npages;
/* we can do it either atomically or asynchronously, not both */
BUG_ON(atomic && async);
BUG_ON(!write_fault && !writable);
if (writable)
*writable = true;
if (hva_to_pfn_fast(addr, atomic, async, write_fault, writable, &pfn))
return pfn;
if (atomic || async)
npages = __get_user_pages_fast(addr, 1, 1, page);
if (atomic)
return KVM_PFN_ERR_FAULT;
if (unlikely(npages != 1) && !atomic) {
might_sleep();
npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
if (npages == 1)
return pfn;
if (writable)
*writable = write_fault;
if (async) {
down_read(&current->mm->mmap_sem);
npages = get_user_page_nowait(current, current->mm,
addr, write_fault, page);
up_read(&current->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;
}
down_read(&current->mm->mmap_sem);
if (npages == -EHWPOISON ||
(!async && check_user_page_hwpoison(addr))) {
pfn = KVM_PFN_ERR_HWPOISON;
goto exit;
}
if (unlikely(npages != 1)) {
struct vm_area_struct *vma;
if (atomic)
return KVM_PFN_ERR_FAULT;
down_read(&current->mm->mmap_sem);
if (npages == -EHWPOISON ||
(!async && check_user_page_hwpoison(addr))) {
up_read(&current->mm->mmap_sem);
return KVM_PFN_ERR_HWPOISON;
}
vma = find_vma_intersection(current->mm, addr, addr+1);
if (vma == NULL)
pfn = KVM_PFN_ERR_FAULT;
else if ((vma->vm_flags & VM_PFNMAP)) {
pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) +
vma->vm_pgoff;
BUG_ON(!kvm_is_mmio_pfn(pfn));
} else {
if (async && (vma->vm_flags & VM_WRITE))
*async = true;
pfn = KVM_PFN_ERR_FAULT;
}
up_read(&current->mm->mmap_sem);
} else
pfn = page_to_pfn(page[0]);
vma = find_vma_intersection(current->mm, addr, addr + 1);
if (vma == NULL)
pfn = KVM_PFN_ERR_FAULT;
else if ((vma->vm_flags & VM_PFNMAP)) {
pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) +
vma->vm_pgoff;
BUG_ON(!kvm_is_mmio_pfn(pfn));
} else {
if (async && (vma->vm_flags & VM_WRITE))
*async = true;
pfn = KVM_PFN_ERR_FAULT;
}
exit:
up_read(&current->mm->mmap_sem);
return pfn;
}