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misc: make topology a 4-tuple of u16s

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This is the second patch in a series intended to let Cloud Hypervisor
support more than 255 vCPUs in guest VMs; the first patch/commit is
https://github.com/cloud-hypervisor/cloud-hypervisor/pull/7231

At the moment, CPU topology in Cloud Hypervisor is using
u8 for components, and somewhat inconsistently:

- struct CpuTopology in vmm/src/vm_config.rs uses four components
  (threads_per_core, cores_per_die, dies_per_package, packages);

- when passed around as a tuple, it is a 3-tuple of u8, with
  some inconsistency:

- in get_x2apic_id in arch/src/x86_64/mod.rs  the three u8
    are assumed to be (correctly)
    threads_per_core, cores_per_die, and dies_per_package, but

- in get_vcpu_topology() in vmm/src/cpu.rs the three-tuple is
    threads_per_core, cores_per_die, and packages (dies_per_package
    is assumed to always be one? not clear).

So for consistency, a 4-tuple is always passed around.

In addition, the types of the tuple components is changed from u8 to
u16, as on x86_64 subcomponents can consume up to 16 bits.

Again, config constraints have not been changed, so this patch
is mostly NOOP.

Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Neel Natu <neelnatu@google.com>
Signed-off-by: Ofir Weisse <oweisse@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
This commit is contained in:
Peter Oskolkov
2025-08-12 22:30:37 +00:00
committed by Rob Bradford
parent 364a0972f0
commit 6e0403a959
7 changed files with 81 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files
arch/src/x86_64/mod.rs
+37 -20
View File
@@ -209,11 +209,11 @@ pub enum Error {
E820Configuration,
}
pub fn get_x2apic_id(cpu_id: u32, topology: Option<(u8, u8, u8)>) -> u32 {
pub fn get_x2apic_id(cpu_id: u32, topology: Option<(u16, u16, u16, u16)>) -> u32 {
if let Some(t) = topology {
let thread_mask_width = u8::BITS - (t.0 - 1).leading_zeros();
let core_mask_width = u8::BITS - (t.1 - 1).leading_zeros();
let die_mask_width = u8::BITS - (t.2 - 1).leading_zeros();
let thread_mask_width = u16::BITS - (t.0 - 1).leading_zeros();
let core_mask_width = u16::BITS - (t.1 - 1).leading_zeros();
let die_mask_width = u16::BITS - (t.2 - 1).leading_zeros();
let thread_id = cpu_id % (t.0 as u32);
let core_id = cpu_id / (t.0 as u32) % (t.1 as u32);
@@ -229,6 +229,13 @@ pub fn get_x2apic_id(cpu_id: u32, topology: Option<(u8, u8, u8)>) -> u32 {
cpu_id
}
pub fn get_max_x2apic_id(topology: (u16, u16, u16, u16)) -> u32 {
get_x2apic_id(
(topology.0 as u32 * topology.1 as u32 * topology.2 as u32 * topology.3 as u32) - 1,
Some(topology),
)
}
#[derive(Copy, Clone, Debug)]
pub enum CpuidReg {
EAX,
@@ -825,7 +832,7 @@ pub fn configure_vcpu(
cpuid: Vec<CpuIdEntry>,
kvm_hyperv: bool,
cpu_vendor: CpuVendor,
topology: Option<(u8, u8, u8)>,
topology: Option<(u16, u16, u16, u16)>,
) -> super::Result<()> {
let x2apic_id = get_x2apic_id(id, topology);
@@ -850,7 +857,7 @@ pub fn configure_vcpu(
assert!(apic_id_patched);
if let Some(t) = topology {
update_cpuid_topology(&mut cpuid, t.0, t.1, t.2, cpu_vendor, id);
update_cpuid_topology(&mut cpuid, t.0, t.1, t.2, t.3, cpu_vendor, id);
}
// The TSC frequency CPUID leaf should not be included when running with HyperV emulation
@@ -953,7 +960,7 @@ pub fn configure_system(
serial_number: Option<&str>,
uuid: Option<&str>,
oem_strings: Option<&[&str]>,
topology: Option<(u8, u8, u8)>,
topology: Option<(u16, u16, u16, u16)>,
) -> super::Result<()> {
// Write EBDA address to location where ACPICA expects to find it
guest_mem
@@ -1361,21 +1368,24 @@ pub fn get_host_cpu_phys_bits(hypervisor: &Arc<dyn hypervisor::Hypervisor>) -> u
fn update_cpuid_topology(
cpuid: &mut Vec<CpuIdEntry>,
threads_per_core: u8,
cores_per_die: u8,
dies_per_package: u8,
threads_per_core: u16,
cores_per_die: u16,
dies_per_package: u16,
packages: u16,
cpu_vendor: CpuVendor,
id: u32,
) {
let x2apic_id = get_x2apic_id(
id,
Some((threads_per_core, cores_per_die, dies_per_package)),
Some((threads_per_core, cores_per_die, dies_per_package, packages)),
);
let thread_width = 8 - (threads_per_core - 1).leading_zeros();
let core_width = (8 - (cores_per_die - 1).leading_zeros()) + thread_width;
let die_width = (8 - (dies_per_package - 1).leading_zeros()) + core_width;
// Note: the topology defined here is per "package" (~NUMA node).
let thread_width = u16::BITS - (threads_per_core - 1).leading_zeros();
let core_width = u16::BITS - (cores_per_die - 1).leading_zeros() + thread_width;
let die_width = u16::BITS - (dies_per_package - 1).leading_zeros() + core_width;
// The very old way: a flat number of logical CPUs per package: CPUID.1H:EBX[23:16] bits.
let mut cpu_ebx = CpuidPatch::get_cpuid_reg(cpuid, 0x1, None, CpuidReg::EBX).unwrap_or(0);
cpu_ebx |= ((dies_per_package as u32) * (cores_per_die as u32) * (threads_per_core as u32))
& (0xff << 16);
@@ -1385,6 +1395,7 @@ fn update_cpuid_topology(
cpu_edx |= 1 << 28;
CpuidPatch::set_cpuid_reg(cpuid, 0x1, None, CpuidReg::EDX, cpu_edx);
// The legacy way: threads+cores per package.
// CPU Topology leaf 0xb
CpuidPatch::set_cpuid_reg(cpuid, 0xb, Some(0), CpuidReg::EAX, thread_width);
CpuidPatch::set_cpuid_reg(
@@ -1407,6 +1418,7 @@ fn update_cpuid_topology(
CpuidPatch::set_cpuid_reg(cpuid, 0xb, Some(1), CpuidReg::ECX, 2 << 8);
CpuidPatch::set_cpuid_reg(cpuid, 0xb, Some(1), CpuidReg::EDX, x2apic_id);
// The modern way: many-level hierarchy (but we here only support four levels).
// CPU Topology leaf 0x1f
CpuidPatch::set_cpuid_reg(cpuid, 0x1f, Some(0), CpuidReg::EAX, thread_width);
CpuidPatch::set_cpuid_reg(
@@ -1721,22 +1733,27 @@ mod tests {
#[test]
fn test_get_x2apic_id() {
let x2apic_id = get_x2apic_id(0, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(0, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 0);
let x2apic_id = get_x2apic_id(1, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(1, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 1);
let x2apic_id = get_x2apic_id(2, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(2, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 2);
let x2apic_id = get_x2apic_id(6, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(6, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 8);
let x2apic_id = get_x2apic_id(7, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(7, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 9);
let x2apic_id = get_x2apic_id(8, Some((2, 3, 1)));
let x2apic_id = get_x2apic_id(8, Some((2, 3, 1, 1)));
assert_eq!(x2apic_id, 10);
let x2apic_id = get_x2apic_id(257, Some((1, 312, 1, 1)));
assert_eq!(x2apic_id, 257);
assert_eq!(255, get_max_x2apic_id((1, 256, 1, 1)));
}
}
arch/src/x86_64/mptable.rs
+1 -1
View File
@@ -136,7 +136,7 @@ pub fn setup_mptable(
offset: GuestAddress,
mem: &GuestMemoryMmap,
num_cpus: u32,
topology: Option<(u8, u8, u8)>,
topology: Option<(u16, u16, u16, u16)>,
) -> Result<()> {
if num_cpus > 0 {
let cpu_id_max = num_cpus - 1;