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

[Elliot Berman <quic_eberman@xxxxxxxxxxx>]

On 2/15/2023 10:38 PM, Greg Kroah-Hartman wrote:
> 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?

I can mention in commit text, too.

> > +	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? >

We're following KVM convention here. The logic is documented in patch 17/26.

Thanks,
Elliot