[RFC 26/33] KVM: x86: hyper-vsm: Allow setting per-VTL memory attributes

[Nicolas Saenz Julienne]

Introduce KVM_SET_MEMORY_ATTRIBUTES ioctl support for VTL KVM devices.
The attributes are stored in an xarray private to the VTL device.

The following memory attributes are supported:
 - KVM_MEMORY_ATTRIBUTE_READ
 - KVM_MEMORY_ATTRIBUTE_WRITE
 - KVM_MEMORY_ATTRIBUTE_EXECUTE
 - KVM_MEMORY_ATTRIBUTE_NO_ACCESS
Although only some combinations are valid, see code comment below.

Signed-off-by: Nicolas Saenz Julienne <nsa...@amazon.com>
---
 arch/x86/kvm/hyperv.c | 61 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0d8402dba596..bcace0258af1 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -62,6 +62,10 @@
  */
 #define HV_EXT_CALL_MAX (HV_EXT_CALL_QUERY_CAPABILITIES + 64)
 
+#define KVM_HV_VTL_ATTRS                                               \
+       (KVM_MEMORY_ATTRIBUTE_READ | KVM_MEMORY_ATTRIBUTE_WRITE |       \
+        KVM_MEMORY_ATTRIBUTE_EXECUTE | KVM_MEMORY_ATTRIBUTE_NO_ACCESS)
+
 static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
                                bool vcpu_kick);
 
@@ -3025,6 +3029,7 @@ int kvm_vm_ioctl_get_hv_vsm_state(struct kvm *kvm, struct 
kvm_hv_vsm_state *stat
 
 struct kvm_hv_vtl_dev {
        int vtl;
+       struct xarray mem_attrs;
 };
 
 static int kvm_hv_vtl_get_attr(struct kvm_device *dev,
@@ -3047,16 +3052,71 @@ static void kvm_hv_vtl_release(struct kvm_device *dev)
 {
        struct kvm_hv_vtl_dev *vtl_dev = dev->private;
 
+       xa_destroy(&vtl_dev->mem_attrs);
        kfree(vtl_dev);
        kfree(dev); /* alloc by kvm_ioctl_create_device, free by .release */
 }
 
+/*
+ * The TLFS lists the valid memory protection combinations (15.9.3):
+ *  - No access
+ *  - Read-only, no execute
+ *  - Read-only, execute
+ *  - Read/write, no execute
+ *  - Read/write, execute
+ */
+static bool kvm_hv_validate_vtl_mem_attributes(struct kvm_memory_attributes 
*attrs)
+{
+       u64 attr = attrs->attributes;
+
+       if (attr & ~KVM_HV_VTL_ATTRS)
+               return false;
+
+       if (attr == KVM_MEMORY_ATTRIBUTE_NO_ACCESS)
+               return true;
+
+       if (!(attr & KVM_MEMORY_ATTRIBUTE_READ))
+               return false;
+
+       return true;
+}
+
+static long kvm_hv_vtl_ioctl(struct kvm_device *dev, unsigned int ioctl,
+                            unsigned long arg)
+{
+       switch (ioctl) {
+       case KVM_SET_MEMORY_ATTRIBUTES: {
+               struct kvm_hv_vtl_dev *vtl_dev = dev->private;
+               struct kvm_memory_attributes attrs;
+               int r;
+
+               if (copy_from_user(&attrs, (void __user *)arg, sizeof(attrs)))
+                       return -EFAULT;
+
+               r = -EINVAL;
+               if (!kvm_hv_validate_vtl_mem_attributes(&attrs))
+                       return r;
+
+               r = kvm_ioctl_set_mem_attributes(dev->kvm, &vtl_dev->mem_attrs,
+                                                KVM_HV_VTL_ATTRS, &attrs);
+               if (r)
+                       return r;
+               break;
+       }
+       default:
+               return -ENOTTY;
+       }
+
+       return 0;
+}
+
 static int kvm_hv_vtl_create(struct kvm_device *dev, u32 type);
 
 static struct kvm_device_ops kvm_hv_vtl_ops = {
        .name = "kvm-hv-vtl",
        .create = kvm_hv_vtl_create,
        .release = kvm_hv_vtl_release,
+       .ioctl = kvm_hv_vtl_ioctl,
        .get_attr = kvm_hv_vtl_get_attr,
 };
 
@@ -3076,6 +3136,7 @@ static int kvm_hv_vtl_create(struct kvm_device *dev, u32 
type)
                        vtl++;
 
        vtl_dev->vtl = vtl;
+       xa_init(&vtl_dev->mem_attrs);
        dev->private = vtl_dev;
 
        return 0;
-- 
2.40.1