KVM: MMU: Keep a reverse mapping of non-writable translations
The current kvm mmu only reverse maps writable translation. This is used
to write-protect a page in case it becomes a pagetable.
But with swapping support, we need a reverse mapping of read-only pages as
well: when we evict a page, we need to remove any mapping to it, whether
writable or not.
Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 14e54e3..bbf5eb4 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -211,8 +211,8 @@
static int is_rmap_pte(u64 pte)
{
- return (pte & (PT_WRITABLE_MASK | PT_PRESENT_MASK))
- == (PT_WRITABLE_MASK | PT_PRESENT_MASK);
+ return pte != shadow_trap_nonpresent_pte
+ && pte != shadow_notrap_nonpresent_pte;
}
static void set_shadow_pte(u64 *sptep, u64 spte)
@@ -488,7 +488,6 @@
{
unsigned long *rmapp;
u64 *spte;
- u64 *prev_spte;
gfn = unalias_gfn(kvm, gfn);
rmapp = gfn_to_rmap(kvm, gfn);
@@ -497,13 +496,11 @@
while (spte) {
BUG_ON(!spte);
BUG_ON(!(*spte & PT_PRESENT_MASK));
- BUG_ON(!(*spte & PT_WRITABLE_MASK));
rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
- prev_spte = spte;
- spte = rmap_next(kvm, rmapp, spte);
- rmap_remove(kvm, prev_spte);
- set_shadow_pte(prev_spte, *prev_spte & ~PT_WRITABLE_MASK);
+ if (is_writeble_pte(*spte))
+ set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
kvm_flush_remote_tlbs(kvm);
+ spte = rmap_next(kvm, rmapp, spte);
}
}
@@ -908,14 +905,18 @@
table = __va(table_addr);
if (level == 1) {
+ int was_rmapped;
+
pte = table[index];
+ was_rmapped = is_rmap_pte(pte);
if (is_shadow_present_pte(pte) && is_writeble_pte(pte))
return 0;
mark_page_dirty(vcpu->kvm, v >> PAGE_SHIFT);
page_header_update_slot(vcpu->kvm, table, v);
table[index] = p | PT_PRESENT_MASK | PT_WRITABLE_MASK |
PT_USER_MASK;
- rmap_add(vcpu, &table[index], v >> PAGE_SHIFT);
+ if (!was_rmapped)
+ rmap_add(vcpu, &table[index], v >> PAGE_SHIFT);
return 0;
}
@@ -1424,10 +1425,8 @@
pt = page->spt;
for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
/* avoid RMW */
- if (pt[i] & PT_WRITABLE_MASK) {
- rmap_remove(kvm, &pt[i]);
+ if (pt[i] & PT_WRITABLE_MASK)
pt[i] &= ~PT_WRITABLE_MASK;
- }
}
}