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Commit 0857b9e9 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
Browse files

KVM: Enable async page fault processing 



If asynchronous hva_to_pfn() is requested call GUP with FOLL_NOWAIT to
avoid sleeping on IO. Check for hwpoison is done at the same time,
otherwise check_user_page_hwpoison() will call GUP again and will put
vcpu to sleep.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 9e02fb96

virt/kvm/kvm_main.c

+21 −2
Original line number Diff line number Diff line
@@ -1037,6 +1037,17 @@ static pfn_t get_fault_pfn(void) 
	return fault_pfn;

}



int get_user_page_nowait(struct task_struct *tsk, struct mm_struct *mm,

	unsigned long start, int write, struct page **page)

{

	int flags = FOLL_TOUCH | FOLL_NOWAIT | FOLL_HWPOISON | FOLL_GET;



	if (write)

		flags |= FOLL_WRITE;



	return __get_user_pages(tsk, mm, start, 1, flags, page, NULL, NULL);

}



static inline int check_user_page_hwpoison(unsigned long addr)

{

	int rc, flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_WRITE;
@@ -1070,7 +1081,14 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, 
		if (writable)

			*writable = write_fault;



		npages = get_user_pages_fast(addr, 1, write_fault, page);

		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) {
@@ -1093,7 +1111,8 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, 
			return get_fault_pfn();



		down_read(&current->mm->mmap_sem);

		if (check_user_page_hwpoison(addr)) {

		if (npages == -EHWPOISON ||

			(!async && check_user_page_hwpoison(addr))) {

			up_read(&current->mm->mmap_sem);

			get_page(hwpoison_page);

			return page_to_pfn(hwpoison_page);