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openvmm_core/loaders: load linux on arm64 based on memory layout #3416

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openvmm_core/loaders: load linux on arm64 based on memory layout #3416

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35 changes: 23 additions & 12 deletions openvmm/openvmm_core/src/worker/vm_loaders/linux.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -785,14 +785,20 @@ pub fn load_linux_arm64(

// Data dependencies:
// - DeviceTree carries the start address of the initrd.
// - The linux loader loads the kernel, the initrd at the said address,
// and the device tree into the guest memory.
// - The linux loader loads the kernel, the initrd at the said address, and
// the device tree into the guest memory.
//
// Thus, we first start with planning the memory layout where
// some space at the loader bottom is reserved for the initrd.

const INITRD_BASE: u64 = 16 << 20; // 16 MB
let initrd_start: u64 = INITRD_BASE;
// Place the initrd at the bottom of guest memory + 16MB, and set the
// minimum kernel address above it, aligned to the next 2MB boundary.
let mem_start = cfg
.mem_layout
.ram()
.first()
.expect("must be at least one ram range")
.range
.start();
const INITRD_OFFSET: u64 = 16 << 20; // 16 MB
let initrd_start: u64 = mem_start + INITRD_OFFSET;
let initrd_end: u64 = initrd_start + initrd_size;
// Align the kernel to 2MB
let kernel_minimum_start_address: u64 = (initrd_end + 0x1fffff) & !0x1fffff;
Expand All @@ -801,13 +807,18 @@ pub fn load_linux_arm64(
// ACPI mode: write EFI + ACPI tables into guest memory, then build a
// minimal "stub" DT that points the kernel's EFI stub at them. The
// kernel discovers all devices through ACPI, not the DT.
const EFI_BASE: u64 = 0x0080_0000; // 8 MB
const EFI_OFFSET: u64 = 0x0080_0000; // 8 MB
const ACPI_TABLES_OFFSET: u64 = 0x2000;
const { assert!(EFI_BASE < INITRD_BASE) };
let rsdp_addr = EFI_BASE + ACPI_TABLES_OFFSET;
const { assert!(EFI_OFFSET < INITRD_OFFSET) };
let rsdp_addr = mem_start + EFI_OFFSET + ACPI_TABLES_OFFSET;
let acpi_tables = build_acpi(rsdp_addr);
let efi_info =
write_efi_and_acpi_tables(gm, EFI_BASE, rsdp_addr, cfg.mem_layout, &acpi_tables)?;
let efi_info = write_efi_and_acpi_tables(
gm,
mem_start + EFI_OFFSET,
rsdp_addr,
cfg.mem_layout,
&acpi_tables,
)?;
build_stub_dt(cfg.cmdline, initrd_start, initrd_end, &efi_info)
.map_err(|e| Error::Dt(DtError(e)))?
} else {
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