KVM: Add kvm_read_guest_atomic()

In preparation for a mmu spinlock, add kvm_read_guest_atomic()
and use it in fetch() and prefetch_page().

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 16 insertions, 12 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 7f83f5557d5e..136a65d72b0a 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -316,10 +316,12 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                                                metaphysical, access,
                                                shadow_ent, &new_page);
                 if (new_page && !metaphysical) {
+                        int r;
                         pt_element_t curr_pte;
-                        kvm_read_guest(vcpu->kvm, walker->pte_gpa[level - 2],
-                                       &curr_pte, sizeof(curr_pte));
-                        if (curr_pte != walker->ptes[level - 2])
+                        r = kvm_read_guest_atomic(vcpu->kvm,
+                                                  walker->pte_gpa[level - 2],
+                                                  &curr_pte, sizeof(curr_pte));
+                        if (r || curr_pte != walker->ptes[level - 2])
                                 return NULL;
                 }
                 shadow_addr = __pa(shadow_page->spt);
@@ -429,9 +431,8 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
 static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *sp)
 {
-        int i, offset = 0;
-        pt_element_t *gpt;
-        struct page *page;
+        int i, offset = 0, r = 0;
+        pt_element_t pt;
 
         if (sp->role.metaphysical
             || (PTTYPE == 32 && sp->role.level > PT_PAGE_TABLE_LEVEL)) {
@@ -441,15 +442,18 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
 
         if (PTTYPE == 32)
                 offset = sp->role.quadrant << PT64_LEVEL_BITS;
-        page = gfn_to_page(vcpu->kvm, sp->gfn);
-        gpt = kmap_atomic(page, KM_USER0);
-        for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
-                if (is_present_pte(gpt[offset + i]))
+
+        for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+                gpa_t pte_gpa = gfn_to_gpa(sp->gfn);
+                pte_gpa += (i+offset) * sizeof(pt_element_t);
+
+                r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &pt,
+                                          sizeof(pt_element_t));
+                if (r || is_present_pte(pt))
                         sp->spt[i] = shadow_trap_nonpresent_pte;
                 else
                         sp->spt[i] = shadow_notrap_nonpresent_pte;
-        kunmap_atomic(gpt, KM_USER0);
-        kvm_release_page_clean(page);
+        }
 }
 
 #undef pt_element_t