KVM: Avoid guest virtual addresses in string pio userspace interface

The current string pio interface communicates using guest virtual addresses,
relying on userspace to translate addresses and to check permissions.  This
interface cannot fully support guest smp, as the check needs to take into
account two pages at one in case an unaligned string transfer straddles a
page boundary.

Change the interface not to communicate guest addresses at all; instead use
a buffer page (mmaped by userspace) and do transfers there.  The kernel
manages the virtual to physical translation and can perform the checks
atomically by taking the appropriate locks.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 2d905770fd88..4843e95e54e1 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -735,6 +735,15 @@ hpa_t gva_to_hpa(struct kvm_vcpu *vcpu, gva_t gva)
 	return gpa_to_hpa(vcpu, gpa);
 }
 
+struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva)
+{
+	gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, gva);
+
+	if (gpa == UNMAPPED_GVA)
+		return NULL;
+	return pfn_to_page(gpa_to_hpa(vcpu, gpa) >> PAGE_SHIFT);
+}
+
 static void nonpaging_new_cr3(struct kvm_vcpu *vcpu)
 {
 }