Re: [PATCH v10 12/26] gunyah: vm_mgr: Add/remove user memory regions

[Greg Kroah-Hartman]

On Tue, Feb 14, 2023 at 01:24:16PM -0800, Elliot Berman wrote:
> 
> When launching a virtual machine, Gunyah userspace allocates memory for
> the guest and informs Gunyah about these memory regions through
> SET_USER_MEMORY_REGION ioctl.

It also frees memory, see below.  Why not document that?

> +	case GH_VM_SET_USER_MEM_REGION: {
> +		struct gh_userspace_memory_region region;
> +
> +		if (copy_from_user(&region, argp, sizeof(region)))
> +			return -EFAULT;
> +
> +		/* All other flag bits are reserved for future use */
> +		if (region.flags & ~(GH_MEM_ALLOW_READ | GH_MEM_ALLOW_WRITE | GH_MEM_ALLOW_EXEC |
> +			GH_MEM_LENT))
> +			return -EINVAL;

Nice, thanks for validating that.


> +
> +

Nit, 2 blank lines are not needed :(


> +		if (region.memory_size)
> +			r = gh_vm_mem_alloc(ghvm, &region);
> +		else
> +			r = gh_vm_mem_free(ghvm, region.label);

So if you set the size to 0 it is freed?  Wouldn't a separate ioctl make
more sense?  Where is this logic documented to userspace?

thanks,

greg k-h