github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

KVM: Only bind memslot to guest_memfd instance for CREATE operations

Browse Source 
For additional defense-in-depth, and to avoid having to handle impossible
unwind scenarios when binding to a memslot fails, bind a memslot to a gmem
instance only for CREATE operations, i.e. don't attempt to establish a
binding for MOVE and FLAGS_ONLY operations.  And when FLAGS_ONLY operations
are eventually supported (this is currently all dead code), creating a new
binding would be incorrect; KVM instead needs to do a 1:1 replacement of
the existing binding, i.e. FLAGS_ONLY will need its own dedicated handling.

Update the relevant TODO to make a better guess as to what needs to be done
to support toggling dirty logging for guest_memfd memslots.

Because it's dead code, no functional change intended.

Cc: stable@vger.kernel.org
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Link: https://patch.msgid.link/20260922001332.1121266-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-09-21 17:13:29 -07:00
parent 23a205797c
commit 513333a554
1 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
virt/kvm/kvm_main.c
View File

@ -1742,10 +1742,10 @@ static void kvm_commit_memory_region(struct kvm *kvm,
kvm_destroy_dirty_bitmap(old);
/*
* Unbind the guest_memfd instance as needed; the @new slot has
* already created its own binding. TODO: Drop the WARN when
* dirty logging guest_memfd memslots is supported. Until then,
* flags-only changes on guest_memfd slots should be impossible.
* TODO: Drop the WARN and do the unbind() call only for MOVE
* when dirty logging guest_memfd memslots is supported. Until
* then, flags-only changes on guest_memfd slots should also be
* impossible; unbind the old memslot for defense-in-depth.
*/
if (WARN_ON_ONCE(old->flags & KVM_MEM_GUEST_MEMFD))
kvm_gmem_unbind(old);
@ -2106,7 +2106,7 @@ static int kvm_set_memory_region(struct kvm *kvm,
new->npages = npages;
new->flags = mem->flags;
new->userspace_addr = mem->userspace_addr;
if (mem->flags & KVM_MEM_GUEST_MEMFD) {
if (change == KVM_MR_CREATE && (mem->flags & KVM_MEM_GUEST_MEMFD)) {
r = kvm_gmem_bind(kvm, new, mem->guest_memfd, mem->guest_memfd_offset);
if (r)
goto out;
@ -2119,7 +2119,7 @@ static int kvm_set_memory_region(struct kvm *kvm,
return 0;
out_unbind:
if (mem->flags & KVM_MEM_GUEST_MEMFD)
if (change == KVM_MR_CREATE && (mem->flags & KVM_MEM_GUEST_MEMFD))
kvm_gmem_unbind(new);
out:
kfree(new);