1# Memory Layout 2 3## x86-64 guest physical memory map 4 5This is a survey of the existing memory layout for crosvm on x86-64 when booting a Linux kernel. Some of these values are different when booting a BIOS image; 6see the source. All addresses are in hexadecimal. 7 8| Name/source link | Address | End (exclusive) | Size | Notes | 9| ---------------------------- | ------------- | --------------- | --------- | ---------------------------------------------------------------------------------------- | 10| [`START_OF_RAM_32BITS`] | `0000` | | | RAM | 11| [`ZERO_PAGE_OFFSET`] | `7000` | | | Linux boot_params structure | 12| [`BOOT_STACK_POINTER`] | `8000` | | | Boot SP value | 13| [`boot_pml4_addr`] | `9000` | `A000` | 4 KiB | Boot page table | 14| [`boot_pdpte_addr`] | `A000` | `B000` | 4 KiB | Boot page table | 15| [`boot_pde_addr`] | `B000` | `F000` | 16 KiB | Boot page tables | 16| [`CMDLINE_OFFSET`] | `2_0000` | `2_0800` | 2 KiB | Linux kernel command line | 17| [`SETUP_DATA_START`] | `2_0800` | `E_0000` | 766 KiB | Linux kernel `setup_data` linked list | 18| [`ACPI_HI_RSDP_WINDOW_BASE`] | `E_0000` | | | ACPI tables | 19| [`KERNEL_START_OFFSET`] | `20_0000` | | | Linux kernel image load address | 20| [`initrd_start`] | after kernel | | | Initial RAM disk for Linux kernel (optional) | 21| [`END_ADDR_BEFORE_32BITS`] | after initrd | `D000_0000` | ~3.24 GiB | RAM (\<4G) | 22| [`PROTECTED_VM_FW_START`] | `CFC0_0000` | `D000_0000` | 4 MiB | pVM firmware (if running a protected VM) | 23| [`END_ADDR_BEFORE_32BITS`] | `D000_0000` | `F400_0000` | 576 MiB | Low (\<4G) MMIO allocation area | 24| [`PCIE_CFG_MMIO_START`] | `F400_0000` | `F800_0000` | 64 MiB | PCIe enhanced config (ECAM) | 25| [`RESERVED_MEM_SIZE`] | `F800_0000` | `1_0000_0000` | 128 MiB | LAPIC/IOAPIC/HPET/… | 26| [`IDENTITY_MAP_ADDR`] | `FEFF_C000` | | | Identity map segment | 27| [`TSS_ADDR`] | `FEFF_D000` | | | Boot task state segment | 28| | `1_0000_0000` | | | RAM (>4G) | 29| | (end of RAM) | | | High (>4G) MMIO allocation area | 30 31[`start_of_ram_32bits`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=351?q=START_OF_RAM_32BITS 32[`zero_page_offset`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=368?q=ZERO_PAGE_OFFSET 33[`boot_stack_pointer`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=350?q=BOOT_STACK_POINTER 34[`boot_pml4_addr`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/regs.rs;l=297?q=boot_pml4_addr 35[`boot_pdpte_addr`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/regs.rs;l=298?q=boot_pdpte_addr 36[`boot_pde_addr`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/regs.rs;l=299?q=boot_pde_addr 37[`cmdline_offset`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=373?q=CMDLINE_OFFSET 38[`setup_data_start`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=375?q=SETUP_DATA_START 39[`acpi_hi_rsdp_window_base`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=388?q=ACPI_HI_RSDP_WINDOW_BASE 40[`kernel_start_offset`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=372?q=KERNEL_START_OFFSET 41[`initrd_start`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=1692?q=initrd_start 42[`protected_vm_fw_start`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=394?q=PROTECTED_VM_FW_START 43[`end_addr_before_32bits`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=356?q=END_ADDR_BEFORE_32BITS 44[`pcie_cfg_mmio_start`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=363?q=PCIE_CFG_MMIO_START 45[`reserved_mem_size`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=358?q=RESERVED_MEM_SIZE 46[`identity_map_addr`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=500?q=identity_map_addr_start 47[`tss_addr`]: https://crsrc.org/o/src/platform/crosvm/x86_64/src/lib.rs;l=505?q=tss_addr_start 48 49## aarch64 guest physical memory map 50 51All addresses are IPA in hexadecimal. 52 53### Common layout 54 55These apply for all boot modes. 56 57| Name/source link | Address | End (exclusive) | Size | Notes | 58| --------------------------------- | --------------- | --------------- | ---------- | ------------------------------------------------------------- | 59| [`SERIAL_ADDR[3]`][serial_addr] | `2e8` | `2f0` | 8 bytes | Serial port MMIO | 60| [`SERIAL_ADDR[1]`][serial_addr] | `2f8` | `300` | 8 bytes | Serial port MMIO | 61| [`SERIAL_ADDR[2]`][serial_addr] | `3e8` | `3f0` | 8 bytes | Serial port MMIO | 62| [`SERIAL_ADDR[0]`][serial_addr] | `3f8` | `400` | 8 bytes | Serial port MMIO | 63| [`AARCH64_RTC_ADDR`] | `2000` | `3000` | 4 KiB | Real-time clock | 64| [`AARCH64_VMWDT_ADDR`] | `3000` | `4000` | 4 KiB | Watchdog device | 65| [`AARCH64_PCI_CAM_BASE_DEFAULT`] | `1_0000` | `101_0000` | 16 MiB | PCI configuration (CAM) | 66| [`AARCH64_VIRTFREQ_BASE`] | `104_0000` | `105_0000` | 64 KiB | Virtual cpufreq device | 67| [`AARCH64_PVTIME_IPA_START`] | `1ff_0000` | `200_0000` | 64 KiB | Paravirtualized time | 68| [`AARCH64_PCI_CAM_BASE_DEFAULT`] | `200_0000` | `400_0000` | 32 MiB | Low MMIO allocation area | 69| [`AARCH64_GIC_CPUI_BASE`] | `3ffd_0000` | `3fff_0000` | 128 KiB | vGIC | 70| [`AARCH64_GIC_DIST_BASE`] | `3fff_0000` | `4000_0000` | 64 KiB | vGIC | 71| [`AARCH64_PROTECTED_VM_FW_START`] | `7fc0_0000` | `8000_0000` | 4 MiB | pVM firmware (if running a protected VM) | 72| [`AARCH64_PHYS_MEM_START`] | `8000_0000` | | --mem size | RAM (starts at IPA = 2 GiB) | 73| [`plat_mmio_base`] | after RAM | +0x800000 | 8 MiB | Platform device MMIO region | 74| [`high_mmio_base`] | after plat_mmio | max phys addr | | High MMIO allocation area | 75 76### RAM Layout 77 78The RAM layout depends on the `--fdt-position` setting, which defaults to 79`start` when load using `--bios` and to `end` when using `--kernel`. 80 81In `--kernel` mode, the initrd is always loaded immediately after the kernel, 82with a 16 MiB alignment. 83 84#### --fdt-position=start 85 86| Name/source link | Address | End (exclusive) | Size | Notes | 87| ------------------------- | ----------------- | --------------- | ----- | -------------------------------- | 88| [`fdt_address`] | `8000_0000` | `8020_0000` | 2 MiB | Flattened device tree in RAM | 89| [`payload_address`] | `8020_0000` | | | Kernel/BIOS load location in RAM | 90 91#### --fdt-position=after-payload 92 93| Name/source link | Address | End (exclusive) | Size | Notes | 94| ------------------------- | ----------------------------------- | --------------- | ----- | -------------------------------- | 95| [`payload_address`] | `8000_0000` | | | Kernel/BIOS load location in RAM | 96| [`fdt_address`] | after payload (2 MiB alignment) | | 2 MiB | Flattened device tree in RAM | 97 98#### --fdt-position=end 99 100| Name/source link | Address | End (exclusive) | Size | Notes | 101| ------------------------- | ----------------------------------- | --------------- | ----- | -------------------------------- | 102| [`payload_address`] | `8000_0000` | | | Kernel/BIOS load location in RAM | 103| [`fdt_address`] | before end of RAM (2 MiB alignment) | | 2 MiB | Flattened device tree in RAM | 104 105[serial_addr]: https://crsrc.org/o/src/platform/crosvm/arch/src/serial.rs;l=78?q=SERIAL_ADDR 106[`aarch64_rtc_addr`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=177?q=AARCH64_RTC_ADDR 107[`aarch64_vmwdt_addr`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=187?q=AARCH64_VMWDT_ADDR 108[`aarch64_pci_cfg_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=192?q=AARCH64_PCI_CAM_BASE_DEFAULT 109[`aarch64_virtfreq_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=207?q=AARCH64_VIRTFREQ_BASE 110[`aarch64_mmio_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=196?q=AARCH64_PCI_CAM_BASE_DEFAULT 111[`aarch64_gic_cpui_base`]: https://crsrc.org/o/src/platform/crosvm/devices/src/irqchip/kvm/aarch64.rs;l=106?q=AARCH64_GIC_CPUI_BASE 112[`aarch64_gic_dist_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=105?q=AARCH64_GIC_DIST_BASE 113[`aarch64_pvtime_ipa_start`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=100?q=AARCH64_PVTIME_IPA_START 114[`aarch64_protected_vm_fw_start`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=96?q=AARCH64_PROTECTED_VM_FW_START 115[`aarch64_phys_mem_start`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=85?q=AARCH64_PHYS_MEM_START 116[`plat_mmio_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=835?q=plat_mmio_base 117[`high_mmio_base`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=838?q=high_mmio_base 118[`fdt_address`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=301?q=fdt_address 119[`payload_address`]: https://crsrc.org/o/src/platform/crosvm/aarch64/src/lib.rs;l=301?q=payload_address 120