feat: added ref to mem alloc kernel api

docs/re.md

@@ -278,6 +278,10 @@ to a number of requirements:
 - 4-KB aligned (aka page-aligned)
 - Its size shall be specified by reading the `IA32_VMX_BASIC[44:32]` MSR (p. 4586)
 
+<!--TODO: how to alloc a page-aligned region ??-->
+> Need to investigate the different allocation strategies[^7] offered by the
+> kernel.
+
 ```c
 #define REGION_SIZE ((__rdmsr(IA32_VMX_BASIC) >> 32) & 0x1fff)
 
@@ -333,3 +337,4 @@ static int vmxon_region_alloc(void) {
 [^4]: [Intel SDM 2024 Vol. 3](https://cdrdv2.intel.com/v1/dl/getContent/671447)
 [^5]: [CPU Registers x86](https://wiki.osdev.org/CPU_Registers_x86)
 [⁶]: [The basics of Intel VT-x extensions](https://research.meekolab.com/the-basics-of-intel-vt-x-extensions#heading-vmxon-execution)
+[^7]: [Memory Allocation Guide](https://www.kernel.org/doc/html/v6.12/core-api/memory-allocation.html#memory-allocation-guide)