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Commit c8cfbb55 authored by Takuya Yoshikawa's avatar Takuya Yoshikawa Committed by Avi Kivity
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KVM: MMU: Use ptep_user for cmpxchg_gpte() 



The address of the gpte was already calculated and stored in ptep_user
before entering cmpxchg_gpte().

This patch makes cmpxchg_gpte() to use that to make it clear that we
are using the same address during walk_addr_generic().

Note that the unlikely annotations are used to show that the conditions
are something unusual rather than for performance.

Signed-off-by: default avatarTakuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 85722cda

arch/x86/kvm/paging_tmpl.h

+12 −14
Original line number Diff line number Diff line
@@ -79,21 +79,19 @@ static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl) 
}



static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,

			 gfn_t table_gfn, unsigned index,

			       pt_element_t __user *ptep_user, unsigned index,

			       pt_element_t orig_pte, pt_element_t new_pte)

{

	int npages;

	pt_element_t ret;

	pt_element_t *table;

	struct page *page;

	gpa_t gpa;



	gpa = mmu->translate_gpa(vcpu, table_gfn << PAGE_SHIFT,

				 PFERR_USER_MASK|PFERR_WRITE_MASK);

	if (gpa == UNMAPPED_GVA)

	npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page);

	/* Check if the user is doing something meaningless. */

	if (unlikely(npages != 1))

		return -EFAULT;



	page = gfn_to_page(vcpu->kvm, gpa_to_gfn(gpa));



	table = kmap_atomic(page, KM_USER0);

	ret = CMPXCHG(&table[index], orig_pte, new_pte);

	kunmap_atomic(table, KM_USER0);
@@ -220,9 +218,9 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
			int ret;

			trace_kvm_mmu_set_accessed_bit(table_gfn, index,

						       sizeof(pte));

			ret = FNAME(cmpxchg_gpte)(vcpu, mmu, table_gfn,

					index, pte, pte|PT_ACCESSED_MASK);

			if (ret < 0) {

			ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index,

						  pte, pte|PT_ACCESSED_MASK);

			if (unlikely(ret < 0)) {

				present = false;

				break;

			} else if (ret)
@@ -279,9 +277,9 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, 
		int ret;



		trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));

		ret = FNAME(cmpxchg_gpte)(vcpu, mmu, table_gfn, index, pte,

			    pte|PT_DIRTY_MASK);

		if (ret < 0) {

		ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index,

					  pte, pte|PT_DIRTY_MASK);

		if (unlikely(ret < 0)) {

			present = false;

			goto error;

		} else if (ret)