KVM: MMU: Partial swapping of guest memory
This allows guest memory to be swapped. Pages which are currently mapped
via shadow page tables are pinned into memory, but all other pages can
be freely swapped.
The patch makes gfn_to_page() elevate the page's reference count, and
introduces kvm_release_page() that pairs with it.
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 2ad14fb..5d7af4b 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -425,6 +425,8 @@
if (!is_rmap_pte(*spte))
return;
page = page_header(__pa(spte));
+ kvm_release_page(pfn_to_page((*spte & PT64_BASE_ADDR_MASK) >>
+ PAGE_SHIFT));
rmapp = gfn_to_rmap(kvm, page->gfns[spte - page->spt]);
if (!*rmapp) {
printk(KERN_ERR "rmap_remove: %p %llx 0->BUG\n", spte, *spte);
@@ -911,6 +913,8 @@
PT_USER_MASK;
if (!was_rmapped)
rmap_add(vcpu, &table[index], v >> PAGE_SHIFT);
+ else
+ kvm_release_page(pfn_to_page(p >> PAGE_SHIFT));
return 0;
}
@@ -925,6 +929,7 @@
1, 3, &table[index]);
if (!new_table) {
pgprintk("nonpaging_map: ENOMEM\n");
+ kvm_release_page(pfn_to_page(p >> PAGE_SHIFT));
return -ENOMEM;
}
@@ -1039,8 +1044,11 @@
paddr = gpa_to_hpa(vcpu->kvm, addr & PT64_BASE_ADDR_MASK);
- if (is_error_hpa(paddr))
+ if (is_error_hpa(paddr)) {
+ kvm_release_page(pfn_to_page((paddr & PT64_BASE_ADDR_MASK)
+ >> PAGE_SHIFT));
return 1;
+ }
return nonpaging_map(vcpu, addr & PAGE_MASK, paddr);
}
@@ -1507,6 +1515,7 @@
} else {
gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, va);
hpa_t hpa = gpa_to_hpa(vcpu, gpa);
+ struct page *page;
if (is_shadow_present_pte(ent)
&& (ent & PT64_BASE_ADDR_MASK) != hpa)
@@ -1519,6 +1528,9 @@
&& !is_error_hpa(hpa))
printk(KERN_ERR "audit: (%s) notrap shadow,"
" valid guest gva %lx\n", audit_msg, va);
+ page = pfn_to_page((gpa & PT64_BASE_ADDR_MASK)
+ >> PAGE_SHIFT);
+ kvm_release_page(page);
}
}