Convert guest virtual address to host physical address

edit

My environment:

Guest : ubuntu-16.04.3-server-amd64.iso (VM) Host . : ubuntu-16.04.3-server-amd64.iso (Nested VM)

I ran the following code in guest:

---[ mmu.c ]---
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <assert.h>
#include <inttypes.h>

#define PAGE_SHIFT  12
#define PAGE_SIZE   (1 << PAGE_SHIFT)
#define PFN_PRESENT (1ull << 63)
#define PFN_PFN     ((1ull << 55) - 1)

int fd;

uint32_t page_offset(uint32_t addr)
{
    return addr & ((1 << PAGE_SHIFT) - 1);
}

uint64_t gva_to_gfn(void *addr)
{
    uint64_t pme, gfn;
    size_t offset;
    offset = ((uintptr_t)addr >> 9) & ~7;
    lseek(fd, offset, SEEK_SET);
    read(fd, &pme, 8);
    if (!(pme & PFN_PRESENT))
        return -1;
    gfn = pme & PFN_PFN;
    return gfn;
}

uint64_t gva_to_gpa(void *addr)
{
    uint64_t gfn = gva_to_gfn(addr);
    assert(gfn != -1);
    return (gfn << PAGE_SHIFT) | page_offset((uint64_t)addr);
}

int main()
{
    uint8_t *ptr;
    uint64_t ptr_mem;

    fd = open("/proc/self/pagemap", O_RDONLY);
    if (fd < 0) {
        perror("open");
        exit(1);
    }

    ptr = malloc(256);
    strcpy(ptr, "Where am I?");
    printf("%s\n", ptr);
    ptr_mem = gva_to_gpa(ptr);
    printf("Your physical address is at 0x%"PRIx64"\n", ptr_mem);

    getchar();
    return 0;
}

output

Where am I? Your physical address is at 0x10

Is 0x10 valid guest physical address ? Else, what I have done wrong here. If it's right, Host physical adddress = Guest Physical address (gpa) + highmem_hva_base

Can anybody please help how to find highmem_hva_base ? What is my phys_mem_base in host?