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>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 7f83f55..136a65d 100644 (file)
--- 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

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9ff5904..a020fb2 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -167,6 +167,8 @@ void kvm_release_page_clean(struct page *page);
 void kvm_release_page_dirty(struct page *page);
 int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
                        int len);
+int kvm_read_guest_atomic(struct kvm *kvm, gpa_t gpa, void *data,
+                         unsigned long len);
 int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
 int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
                         int offset, int len);

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 678e805..8d0b7c1 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -541,6 +541,26 @@ int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len)
 }
 EXPORT_SYMBOL_GPL(kvm_read_guest);
 
+int kvm_read_guest_atomic(struct kvm *kvm, gpa_t gpa, void *data,
+                         unsigned long len)
+{
+       int r;
+       unsigned long addr;
+       gfn_t gfn = gpa >> PAGE_SHIFT;
+       int offset = offset_in_page(gpa);
+
+       addr = gfn_to_hva(kvm, gfn);
+       if (kvm_is_error_hva(addr))
+               return -EFAULT;
+       pagefault_disable();
+       r = __copy_from_user_inatomic(data, (void __user *)addr + offset, len);
+       pagefault_enable();
+       if (r)
+               return -EFAULT;
+       return 0;
+}
+EXPORT_SYMBOL(kvm_read_guest_atomic);
+
 int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
                         int offset, int len)
 {