[patch 2/5] KVM: add kvm_read_guest_atomic()

Marcelo Tosatti
2007-12-21T00:18:23Z

[-- Attachment #1: mmu-atomicity --]
[-- Type: text/plain, Size: 3849 bytes --]

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-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Index: kvm.quilt/arch/x86/kvm/paging_tmpl.h
===================================================================
--- kvm.quilt.orig/arch/x86/kvm/paging_tmpl.h
+++ kvm.quilt/arch/x86/kvm/paging_tmpl.h
@@ -318,10 +318,12 @@ static u64 *FNAME(fetch)(struct kvm_vcpu
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);
@@ -431,9 +433,8 @@ static gpa_t FNAME(gva_to_gpa)(struct kv
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)) {
@@ -443,15 +444,18 @@ static void FNAME(prefetch_page)(struct

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
Index: kvm.quilt/include/linux/kvm_host.h
===================================================================
--- kvm.quilt.orig/include/linux/kvm_host.h
+++ kvm.quilt/include/linux/kvm_host.h
@@ -167,6 +167,8 @@ void kvm_release_page_clean(struct 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);
Index: kvm.quilt/virt/kvm/kvm_main.c
===================================================================
--- kvm.quilt.orig/virt/kvm/kvm_main.c
+++ kvm.quilt/virt/kvm/kvm_main.c
@@ -541,6 +541,26 @@ int kvm_read_guest(struct kvm *kvm, gpa_
}
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)
{