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

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