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

[Elliot Berman]

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