I am implementing 'virtio-pmem' as a mechanism to
flush guest writes with 'fake DAX' flushing interface.
Below is the high level details of components:
1] 'virtio-pmem' device expose guest physical address
2] 'virtio-pmem' driver in guest discovers this
information and configures 'libnvdimm'. Guest 'pmem'
driver works on this memory range.
3] Guest 'pmem' driver uses 'virtio-pmem' PV driver to
send flush commands.
I need suggestion implementing part 1]
* When tried with 'hotplug_memory.base' address as guest physical
address, I am facing 'EPT_MISCONFIG' errors when pmem does mkfs.
After digging more it looks like address range I am using as guest
physical address is either already mapped as MMIO or reserved.
Though Guest hot-plugs this physical address into its virtual
memory range when guest tries to read/write the memory KVM cannot
translate the address and throw 'EPT_MISCONFIG' error.
* While I am trying to get the appropriate guest physical address
which is free, I could see memory 'pc_dimm_memory_plug' code
has a function 'pc_dimm_get_free_addr' which works with 'PC DIMM'
class. As I am using 'VIRTIO', there is no way AFAIK this function
can be used by VIRTIO or my PV device code.
I need ideas to get the free guest physical address from my PV
device code so that we can use this range in guest address space.
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