On 21/03/2023 16:49, Oliver Upton wrote:
Hi Suzuki,
On Tue, Mar 21, 2023 at 09:53:06AM +0000, Suzuki K Poulose wrote:
On 20/03/2023 22:09, Oliver Upton wrote:
A subsequent change will allow userspace to convey a filter for
hypercalls through a vm device attribute. Add the requisite boilerplate
for vm attribute accessors.
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
---
arch/arm64/kvm/arm.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3bd732eaf087..b6e26c0e65e5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1439,11 +1439,28 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
}
}
+static int kvm_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ switch (attr->group) {
+ default:
+ return -ENXIO;
+ }
+}
+
+static int kvm_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ switch (attr->group) {
+ default:
+ return -ENXIO;
+ }
+}
+
long kvm_arch_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
struct kvm *kvm = filp->private_data;
void __user *argp = (void __user *)arg;
+ struct kvm_device_attr attr;
switch (ioctl) {
case KVM_CREATE_IRQCHIP: {
@@ -1479,6 +1496,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
return -EFAULT;
return kvm_vm_ioctl_mte_copy_tags(kvm, ©_tags);
}
+ case KVM_HAS_DEVICE_ATTR: {
+ if (copy_from_user(&attr, argp, sizeof(attr)))
+ return -EFAULT;
+
+ return kvm_vm_has_attr(kvm, &attr);
+ }
+ case KVM_SET_DEVICE_ATTR: {
+ if (copy_from_user(&attr, argp, sizeof(attr)))
+ return -EFAULT;
+
+ return kvm_vm_set_attr(kvm, &attr);
+ }
Is there a reason to exclude KVM_GET_DEVICE_ATTR handling ?
The GET_DEVICE_ATTR would effectively be dead code, as the hypercall filter is
a write-only attribute. The filter is constructed through iterative calls to
the attribute, so conveying the end result to userspace w/ the same UAPI
is non-trivial.
Hopefully userspace remembers what it wrote to the field ;-)
Fair enough. I am thinking of using VM DEVICE_ATTR for some of the Arm
CCA Realm Configuration, which are now overloaded with ENABLE_CAP.
We could add GET_DEVICE_ATTR if and when we need it.
Thanks
Suzuki
