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vmm: raise the (v)CPU limit on kvm/x86_64

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Raise the max number of supported (v)CPUs on kvm x86_64 hosts
to 8192 (the max allowed value of CONFIG_NR_CPUS in the Linux kernel).

Other platfroms keep their existing CPU limits pending further
development and testing.

The change has been tested on Intel and AMD hosts.

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
2025-09-05 20:36:25 +00:00
committed by Bo Chen
parent 57bc78da4f
commit 05d222f0eb
6 changed files with 97 additions and 45 deletions
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56
vmm/src/cpu.rs
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@@ -196,8 +196,8 @@ pub enum Error {
#[error("Error setting up AMX")]
AmxEnable(#[source] anyhow::Error),
#[error("Maximum number of vCPUs exceeds host limit")]
MaximumVcpusExceeded,
#[error("Maximum number of vCPUs {0} exceeds host limit {1}")]
MaximumVcpusExceeded(u32, u32),
#[cfg(feature = "sev_snp")]
#[error("Failed to set sev control register")]
@@ -698,12 +698,16 @@ impl CpuManager {
numa_nodes: &NumaNodes,
#[cfg(feature = "sev_snp")] sev_snp_enabled: bool,
) -> Result<Arc<Mutex<CpuManager>>> {
if u32::from(config.max_vcpus) > hypervisor.get_max_vcpus() {
return Err(Error::MaximumVcpusExceeded);
if config.max_vcpus > hypervisor.get_max_vcpus() {
return Err(Error::MaximumVcpusExceeded(
config.max_vcpus,
hypervisor.get_max_vcpus(),
));
}
let mut vcpu_states = Vec::with_capacity(usize::from(config.max_vcpus));
vcpu_states.resize_with(usize::from(config.max_vcpus), VcpuState::default);
let max_vcpus = usize::try_from(config.max_vcpus).unwrap();
let mut vcpu_states = Vec::with_capacity(max_vcpus);
vcpu_states.resize_with(max_vcpus, VcpuState::default);
let hypervisor_type = hypervisor.hypervisor_type();
#[cfg(target_arch = "x86_64")]
let cpu_vendor = hypervisor.get_cpu_vendor();
@@ -755,7 +759,7 @@ impl CpuManager {
let affinity = if let Some(cpu_affinity) = config.affinity.as_ref() {
cpu_affinity
.iter()
.map(|a| (a.vcpu as u32, a.host_cpus.clone()))
.map(|a| (a.vcpu, a.host_cpus.clone()))
.collect()
} else {
BTreeMap::new()
@@ -781,7 +785,7 @@ impl CpuManager {
#[cfg(feature = "guest_debug")]
vm_debug_evt,
selected_cpu: 0,
vcpus: Vec::with_capacity(usize::from(config.max_vcpus)),
vcpus: Vec::with_capacity(max_vcpus),
seccomp_action,
vm_ops,
acpi_address: None,
@@ -895,10 +899,10 @@ impl CpuManager {
},
|t| {
(
t.threads_per_core.into(),
t.cores_per_die.into(),
t.dies_per_package.into(),
t.packages.into(),
t.threads_per_core,
t.cores_per_die,
t.dies_per_package,
t.packages,
)
},
);
@@ -934,7 +938,7 @@ impl CpuManager {
self.present_vcpus()
);
if desired_vcpus > self.config.max_vcpus as u32 {
if desired_vcpus > self.config.max_vcpus {
return Err(Error::DesiredVCpuCountExceedsMax);
}
@@ -1245,7 +1249,7 @@ impl CpuManager {
inserting: bool,
paused: Option<bool>,
) -> Result<()> {
if desired_vcpus > self.config.max_vcpus as u32 {
if desired_vcpus > self.config.max_vcpus {
return Err(Error::DesiredVCpuCountExceedsMax);
}
@@ -1418,11 +1422,11 @@ impl CpuManager {
}
pub fn boot_vcpus(&self) -> u32 {
self.config.boot_vcpus as u32
self.config.boot_vcpus
}
pub fn max_vcpus(&self) -> u32 {
self.config.max_vcpus as u32
self.config.max_vcpus
}
#[cfg(target_arch = "x86_64")]
@@ -1456,10 +1460,10 @@ impl CpuManager {
pub fn get_vcpu_topology(&self) -> Option<(u16, u16, u16, u16)> {
self.config.topology.clone().map(|t| {
(
t.threads_per_core.into(),
t.cores_per_die.into(),
t.dies_per_package.into(),
t.packages.into(),
t.threads_per_core,
t.cores_per_die,
t.dies_per_package,
t.packages,
)
})
}
@@ -1475,7 +1479,7 @@ impl CpuManager {
{
madt.write(36, arch::layout::APIC_START.0);
for cpu in 0..self.config.max_vcpus as u32 {
for cpu in 0..self.config.max_vcpus {
let x2apic_id = get_x2apic_id(cpu, self.get_vcpu_topology());
let lapic = LocalX2Apic {
@@ -1483,7 +1487,7 @@ impl CpuManager {
length: 16,
processor_id: cpu,
apic_id: x2apic_id,
flags: if cpu < self.config.boot_vcpus as u32 {
flags: if cpu < self.config.boot_vcpus {
1 << MADT_CPU_ENABLE_FLAG
} else {
0
@@ -1535,8 +1539,8 @@ impl CpuManager {
r#type: acpi::ACPI_APIC_GENERIC_CPU_INTERFACE,
length: 80,
reserved0: 0,
cpu_interface_number: cpu as u32,
uid: cpu as u32,
cpu_interface_number: cpu,
uid: cpu,
flags: 1,
parking_version: 0,
performance_interrupt: 0,
@@ -2274,7 +2278,7 @@ impl Aml for CpuManager {
let uid = aml::Name::new("_CID".into(), &aml::EISAName::new("PNP0A05"));
// Bundle methods together under a common object
let methods = CpuMethods {
max_vcpus: self.config.max_vcpus as u32,
max_vcpus: self.config.max_vcpus,
dynamic: self.dynamic,
};
let mut cpu_data_inner: Vec<&dyn Aml> = vec![&hid, &uid, &methods];
@@ -2282,7 +2286,7 @@ impl Aml for CpuManager {
#[cfg(target_arch = "x86_64")]
let topology = self.get_vcpu_topology();
let mut cpu_devices = Vec::new();
for cpu_id in 0..(self.config.max_vcpus as u32) {
for cpu_id in 0..self.config.max_vcpus {
let proximity_domain = *self.proximity_domain_per_cpu.get(&cpu_id).unwrap_or(&0);
let cpu_device = Cpu {
cpu_id,