vmm: Fix compiling error with BHYVE_SNAPSHOT

[gusev.vitaliy_gmail.com]

Summary

error: ignoring return value of function declared with 'warn_unused_result'

sys/amd64/vmm/vmm_snapshot.c:73:3: error: ignoring return value of function
declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]

copyin(buffer->buf, data, data_size);

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[markj]

sys/amd64/vmm/vmm_snapshot.c

103

memcmp() doesn't return an error value. The code should do something like:

error = memcmp(...) != 0 ? EINVAL : 0;

Also, shouldn't there be a copyin()?

This function is rather strange - does it get used anywhere? I can't find any callers.

[gusev.vitaliy_gmail.com]

Removed vm_snapshot_buf_cmp() function in the kernel code.

sys/amd64/vmm/vmm_snapshot.c

103

Yes, you are right, it is only used in userspace via SNAPSHOT_VAR_CMP_OR_LEAVE() in usr.sbin/bhyve/virtio.c :

vi_pci_snapshot_consts[867]    SNAPSHOT_VAR_CMP_OR_LEAVE(vc->vc_nvq, meta, ret, done);
vi_pci_snapshot_consts[868]    SNAPSHOT_VAR_CMP_OR_LEAVE(vc->vc_cfgsize, meta, ret, done);
vi_pci_snapshot_consts[869]    SNAPSHOT_VAR_CMP_OR_LEAVE(vc->vc_hv_caps, meta, ret, done);
vi_pci_snapshot_queues[892]    SNAPSHOT_VAR_CMP_OR_LEAVE(vq->vq_qsize, meta, ret, done);
vi_pci_snapshot_queues[893]    SNAPSHOT_VAR_CMP_OR_LEAVE(vq->vq_num, meta, ret, done);

And current usage memcmp() in kernel with userspace buffer is not safe. So I removed this function for the kernel code.

[gusev.vitaliy_gmail.com]

removed vm_snapshot_buf_cmp() in the kernel code

[markj]

Looks good to me, aside from the comment.

sys/amd64/include/vmm_snapshot.h

100–101

The function prototype should also be guarded by #ifndef _KERNEL.

[gusev.vitaliy_gmail.com]

Move vm_snapshot_buf_cmp prototype under #ifndef _KERNEL.