This will allow us to use the subpage protection feature.
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
virt/kvm/kvmi.c | 46 +++++++++++++++++++++++++++++++++++++--------
virt/kvm/kvmi_int.h | 1 +
2 files changed, 39 insertions(+), 8 deletions(-)
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index 4a9a4430a460..e18dfffa25ac 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -32,6 +32,7 @@ static void kvmi_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
static const u8 full_access = KVMI_PAGE_ACCESS_R |
KVMI_PAGE_ACCESS_W |
KVMI_PAGE_ACCESS_X;
+static const u32 default_write_access_bitmap;
void *kvmi_msg_alloc(void)
{
@@ -57,23 +58,32 @@ static struct kvmi_mem_access *__kvmi_get_gfn_access(struct kvmi *ikvm,
return radix_tree_lookup(&ikvm->access_tree, gfn);
}
+/*
+ * TODO: intercept any SPP change made on pages present in our radix tree.
+ *
+ * bitmap must have the same value as the corresponding SPPT entry.
+ */
static int kvmi_get_gfn_access(struct kvmi *ikvm, const gfn_t gfn,
- u8 *access)
+ u8 *access, u32 *write_bitmap)
{
struct kvmi_mem_access *m;
+ *write_bitmap = default_write_access_bitmap;
*access = full_access;
read_lock(&ikvm->access_tree_lock);
m = __kvmi_get_gfn_access(ikvm, gfn);
- if (m)
+ if (m) {
*access = m->access;
+ *write_bitmap = m->write_bitmap;
+ }
read_unlock(&ikvm->access_tree_lock);
return m ? 0 : -1;
}
-static int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access)
+static int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access,
+ u32 write_bitmap)
{
struct kvmi_mem_access *m;
struct kvmi_mem_access *__m;
@@ -87,6 +97,7 @@ static int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access)
m->gfn = gfn;
m->access = access;
+ m->write_bitmap = write_bitmap;
if (radix_tree_preload(GFP_KERNEL)) {
err = -KVM_ENOMEM;
@@ -100,6 +111,7 @@ static int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access)
__m = __kvmi_get_gfn_access(ikvm, gfn);
if (__m) {
__m->access = access;
+ __m->write_bitmap = write_bitmap;
kvmi_arch_update_page_tracking(kvm, NULL, __m);
if (access == full_access) {
radix_tree_delete(&ikvm->access_tree, gfn);
@@ -124,12 +136,22 @@ static int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access)
return err;
}
+static bool spp_access_allowed(gpa_t gpa, unsigned long bitmap)
+{
+ u32 off = (gpa & ~PAGE_MASK);
+ u32 spp = off / 128;
+
+ return test_bit(spp, &bitmap);
+}
+
static bool kvmi_restricted_access(struct kvmi *ikvm, gpa_t gpa, u8 access)
{
+ u32 allowed_bitmap;
u8 allowed_access;
int err;
- err = kvmi_get_gfn_access(ikvm, gpa_to_gfn(gpa), &allowed_access);
+ err = kvmi_get_gfn_access(ikvm, gpa_to_gfn(gpa), &allowed_access,
+ &allowed_bitmap);
if (err)
return false;
@@ -138,8 +160,14 @@ static bool kvmi_restricted_access(struct kvmi *ikvm, gpa_t gpa, u8 access)
* We want to be notified only for violations involving access
* bits that we've specifically cleared
*/
- if ((~allowed_access) & access)
+ if ((~allowed_access) & access) {
+ bool write_access = (access & KVMI_PAGE_ACCESS_W);
+
+ if (write_access && spp_access_allowed(gpa, allowed_bitmap))
+ return false;
+
return true;
+ }
return false;
}
@@ -1126,8 +1154,9 @@ void kvmi_handle_requests(struct kvm_vcpu *vcpu)
int kvmi_cmd_get_page_access(struct kvmi *ikvm, u64 gpa, u8 *access)
{
gfn_t gfn = gpa_to_gfn(gpa);
+ u32 ignored_write_bitmap;
- kvmi_get_gfn_access(ikvm, gfn, access);
+ kvmi_get_gfn_access(ikvm, gfn, access, &ignored_write_bitmap);
return 0;
}
@@ -1136,10 +1165,11 @@ int kvmi_cmd_set_page_access(struct kvmi *ikvm, u64 gpa, u8 access)
{
gfn_t gfn = gpa_to_gfn(gpa);
u8 ignored_access;
+ u32 write_bitmap;
- kvmi_get_gfn_access(ikvm, gfn, &ignored_access);
+ kvmi_get_gfn_access(ikvm, gfn, &ignored_access, &write_bitmap);
- return kvmi_set_gfn_access(ikvm->kvm, gfn, access);
+ return kvmi_set_gfn_access(ikvm->kvm, gfn, access, write_bitmap);
}
int kvmi_cmd_control_events(struct kvm_vcpu *vcpu, unsigned int event_id,
diff --git a/virt/kvm/kvmi_int.h b/virt/kvm/kvmi_int.h
index 3f0c7a03b4a1..d9a10a3b7082 100644
--- a/virt/kvm/kvmi_int.h
+++ b/virt/kvm/kvmi_int.h
@@ -141,6 +141,7 @@ struct kvmi {
struct kvmi_mem_access {
gfn_t gfn;
u8 access;
+ u32 write_bitmap;
struct kvmi_arch_mem_access arch;
};
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