On Fri, Oct 27, 2023 at 11:21:55AM -0700, Sean Christopherson wrote:

From: Chao Peng <redacted>

In confidential computing usages, whether a page is private or shared is
necessary information for KVM to perform operations like page fault
handling, page zapping etc. There are other potential use cases for
per-page memory attributes, e.g. to make memory read-only (or no-exec,
or exec-only, etc.) without having to modify memslots.

Introduce two ioctls (advertised by KVM_CAP_MEMORY_ATTRIBUTES) to allow
userspace to operate on the per-page memory attributes.
 - KVM_SET_MEMORY_ATTRIBUTES to set the per-page memory attributes to
   a guest memory range.

 - KVM_GET_SUPPORTED_MEMORY_ATTRIBUTES to return the KVM supported
   memory attributes.

This ioctl() is already removed. So, the changelog is out-of-date and needs
an update.

+
+:Capability: KVM_CAP_MEMORY_ATTRIBUTES
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_memory_attributes(in)

					   ^ add one space here?

+static bool kvm_pre_set_memory_attributes(struct kvm *kvm,
+					  struct kvm_gfn_range *range)
+{
+	/*
+	 * Unconditionally add the range to the invalidation set, regardless of
+	 * whether or not the arch callback actually needs to zap SPTEs.  E.g.
+	 * if KVM supports RWX attributes in the future and the attributes are
+	 * going from R=>RW, zapping isn't strictly necessary.  Unconditionally
+	 * adding the range allows KVM to require that MMU invalidations add at
+	 * least one range between begin() and end(), e.g. allows KVM to detect
+	 * bugs where the add() is missed.  Rexlaing the rule *might* be safe,

					    ^^^^^^^^ Relaxing

This cannot work, e.g., no @argp in this function and is fixed by a later commit:

	fcbef1e5e5d2 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")