Re: [PATCH v3 3/9] kvm: kvm_luo: Allow kvm preservation with LUO

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] The macro `KHOSER_COPY_TYPEUNSAFE` is undefined in the kernel tree, causing a build failure.
- [Low] `KHOSER_LOAD_PTR` is incorrectly invoked with a `u64` argument instead of a union, causing a build failure.
--

commit c233e1cbb1e57dbd4789fe720442add1dfd010f1
Author: Tarun Sahu <tarunsahu@google.com>

kvm: kvm_luo: Allow kvm preservation with LUO

This commit introduces KVM VM preservation support for the Live Update
Orchestrator (LUO). It registers a file handler to serialize and deserialize
VM state across live updates, primarily focusing on preserving the VM type.

> diff --git a/virt/kvm/kvm_luo.c b/virt/kvm/kvm_luo.c
> new file mode 100644
> index 0000000000000..6728877f16daf
> --- /dev/null
> +++ b/virt/kvm/kvm_luo.c
> @@ -0,0 +1,195 @@

[ ... ]

> +static int kvm_luo_preserve(struct liveupdate_file_op_args *args)
> +{
> +	DECLARE_KHOSER_PTR(sd, struct kvm_luo_ser *);
> +	struct kvm *kvm = args->file->private_data;
> +	struct kvm_luo_ser *ser;

[ ... ]

> +	KHOSER_STORE_PTR(sd, ser);
> +	KHOSER_COPY_TYPEUNSAFE(args->serialized_data, sd);

[Severity: Low]
Is this macro defined somewhere else in the tree?  It looks like
KHOSER_COPY_TYPEUNSAFE is missing from <linux/kho/abi/kexec_handover.h>
and other headers, which causes a build failure here.

> +
> +	return 0;
> +}
> +
> +static atomic_t restored_vm_id = ATOMIC_INIT(0);
> +
> +static int kvm_luo_retrieve(struct liveupdate_file_op_args *args)
> +{
> +	char fdname[ITOA_MAX_LEN + 1];
> +	struct kvm_luo_ser *ser;
> +	struct file *file;
> +	struct kvm *kvm;
> +	int err = 0;
> +
> +	ser = KHOSER_LOAD_PTR(args->serialized_data);

[Severity: Low]
Does this code compile? KHOSER_LOAD_PTR() expects its argument to be a union
declared with DECLARE_KHOSER_PTR(), which provides the expected .ptr and
.phys fields.

Since args->serialized_data is a plain u64, this causes a compilation error
because it tries to access struct/union members on a primitive type.

> +	if (!ser)
> +		return -EINVAL;
> +
> +	snprintf(fdname, sizeof(fdname), "%d",
> +		 atomic_inc_return(&restored_vm_id));
> +
> +	file = kvm_create_vm_file(ser->type, fdname);

[ ... ]

> +static void kvm_luo_unpreserve(struct liveupdate_file_op_args *args)
> +{
> +	struct kvm_luo_ser *ser;
> +
> +	/*
> +	 * in case preservation failed, args->serialized_data will
> +	 * be NULL and kvm_luo_preserve takes care of cleaning up.
> +	 * If preserve succeeds, this condition fails and unpreserve
> +	 * function takes care of cleaning up.
> +	 */
> +	ser = KHOSER_LOAD_PTR(args->serialized_data);

[Severity: Low]
Similar to the issue in kvm_luo_retrieve(), args->serialized_data is a plain
u64 rather than the union KHOSER_LOAD_PTR() expects. Will this cause a build
failure?

> +	if (WARN_ON_ONCE(!ser))
> +		return;
> +
> +	kho_unpreserve_free(ser);
> +}
> +
> +static void kvm_luo_finish(struct liveupdate_file_op_args *args)
> +{
> +	struct kvm_luo_ser *ser;
> +
> +	/*
> +	 * If retrieve_status is true or set to error, nothing to do here.
> +	 * Already cleaned up in kvm_luo_retrieve().
> +	 */
> +	if (args->retrieve_status)
> +		return;
> +
> +	ser = KHOSER_LOAD_PTR(args->serialized_data);

[Severity: Low]
Is there a type mismatch here as well? args->serialized_data is being passed
to KHOSER_LOAD_PTR() as a plain u64.

> +	if (!ser)
> +		return;
> +
> +	kho_restore_free(ser);
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260622184851.2309827-1-tarunsahu@google.com?part=3