diff options
| -rw-r--r-- | arch/x86/kvm/vmx/main.c | 1 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx/tdx.c | 51 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 2 |
3 files changed, 54 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c index 97737948774a..e0806dbe7b87 100644 --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -7,6 +7,7 @@ #include "pmu.h" #include "posted_intr.h" #include "tdx.h" +#include "tdx_arch.h" static __init int vt_hardware_setup(void) { diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 57eab6fc9f89..cebe570f2002 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -376,6 +376,19 @@ int tdx_vm_init(struct kvm *kvm) kvm->arch.has_protected_state = true; kvm->arch.has_private_mem = true; + /* + * TDX has its own limit of maximum vCPUs it can support for all + * TDX guests in addition to KVM_MAX_VCPUS. TDX module reports + * such limit via the MAX_VCPU_PER_TD global metadata. In + * practice, it reflects the number of logical CPUs that ALL + * platforms that the TDX module supports can possibly have. + * + * Limit TDX guest's maximum vCPUs to the number of logical CPUs + * the platform has. Simply forwarding the MAX_VCPU_PER_TD to + * userspace would result in an unpredictable ABI. + */ + kvm->max_vcpus = min_t(int, kvm->max_vcpus, num_present_cpus()); + /* Place holder for TDX specific logic. */ return __tdx_td_init(kvm); } @@ -695,6 +708,7 @@ static int __init __do_tdx_bringup(void) static int __init __tdx_bringup(void) { + const struct tdx_sys_info_td_conf *td_conf; int r; /* @@ -728,6 +742,43 @@ static int __init __tdx_bringup(void) goto get_sysinfo_err; /* + * TDX has its own limit of maximum vCPUs it can support for all + * TDX guests in addition to KVM_MAX_VCPUS. Userspace needs to + * query TDX guest's maximum vCPUs by checking KVM_CAP_MAX_VCPU + * extension on per-VM basis. + * + * TDX module reports such limit via the MAX_VCPU_PER_TD global + * metadata. Different modules may report different values. + * Some old module may also not support this metadata (in which + * case this limit is U16_MAX). + * + * In practice, the reported value reflects the maximum logical + * CPUs that ALL the platforms that the module supports can + * possibly have. + * + * Simply forwarding the MAX_VCPU_PER_TD to userspace could + * result in an unpredictable ABI. KVM instead always advertise + * the number of logical CPUs the platform has as the maximum + * vCPUs for TDX guests. + * + * Make sure MAX_VCPU_PER_TD reported by TDX module is not + * smaller than the number of logical CPUs, otherwise KVM will + * report an unsupported value to userspace. + * + * Note, a platform with TDX enabled in the BIOS cannot support + * physical CPU hotplug, and TDX requires the BIOS has marked + * all logical CPUs in MADT table as enabled. Just use + * num_present_cpus() for the number of logical CPUs. + */ + td_conf = &tdx_sysinfo->td_conf; + if (td_conf->max_vcpus_per_td < num_present_cpus()) { + pr_err("Disable TDX: MAX_VCPU_PER_TD (%u) smaller than number of logical CPUs (%u).\n", + td_conf->max_vcpus_per_td, num_present_cpus()); + r = -EINVAL; + goto get_sysinfo_err; + } + + /* * Leave hardware virtualization enabled after TDX is enabled * successfully. TDX CPU hotplug depends on this. */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 2a2d2b6c283e..a4d1f3319a5b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4720,6 +4720,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) break; case KVM_CAP_MAX_VCPUS: r = KVM_MAX_VCPUS; + if (kvm) + r = kvm->max_vcpus; break; case KVM_CAP_MAX_VCPU_ID: r = KVM_MAX_VCPU_IDS; |