On Sun, 12 Mar 2023 10:55:42 -0700 isaku.yamahata@xxxxxxxxx wrote: > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > TDX has its own limitation on the maximum number of vcpus that the guest > can accommodate. Allow x86 kvm backend to implement its own KVM_ENABLE_CAP > handler and implement TDX backend for KVM_CAP_MAX_VCPUS. user space VMM, > e.g. qemu, can specify its value instead of KVM_MAX_VCPUS. > I think enabling the cap here is actually "configuring the cap". KVM_CAP_MAX _VCPUS is actually always enabled whether userspace enables it or not. It would be nice to configure of the max VCPUS in kvm_arch_vm_ioctl() where routines of configuring a VM should belong. E.g. KVM_SET_MAX_VCPUS. > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > --- > arch/x86/include/asm/kvm-x86-ops.h | 2 ++ > arch/x86/include/asm/kvm_host.h | 2 ++ > arch/x86/kvm/vmx/main.c | 22 ++++++++++++++++++++++ > arch/x86/kvm/vmx/tdx.c | 30 ++++++++++++++++++++++++++++++ > arch/x86/kvm/vmx/tdx.h | 3 +++ > arch/x86/kvm/vmx/x86_ops.h | 2 ++ > arch/x86/kvm/x86.c | 4 ++++ > 7 files changed, 65 insertions(+) > > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h > index 58fbaa05fc8c..7522c193f2b4 100644 > --- a/arch/x86/include/asm/kvm-x86-ops.h > +++ b/arch/x86/include/asm/kvm-x86-ops.h > @@ -21,6 +21,8 @@ KVM_X86_OP(hardware_unsetup) > KVM_X86_OP(has_emulated_msr) > KVM_X86_OP(vcpu_after_set_cpuid) > KVM_X86_OP(is_vm_type_supported) > +KVM_X86_OP_OPTIONAL(max_vcpus); > +KVM_X86_OP_OPTIONAL(vm_enable_cap) > KVM_X86_OP(vm_init) > KVM_X86_OP_OPTIONAL(vm_destroy) > KVM_X86_OP_OPTIONAL_RET0(vcpu_precreate) > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 49e3ca89aced..d98d61e5213d 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1562,7 +1562,9 @@ struct kvm_x86_ops { > void (*vcpu_after_set_cpuid)(struct kvm_vcpu *vcpu); > > bool (*is_vm_type_supported)(unsigned long vm_type); > + int (*max_vcpus)(struct kvm *kvm); > unsigned int vm_size; > + int (*vm_enable_cap)(struct kvm *kvm, struct kvm_enable_cap *cap); > int (*vm_init)(struct kvm *kvm); > void (*vm_destroy)(struct kvm *kvm); > > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c > index 8ddd263eeabc..68bb320d0b6d 100644 > --- a/arch/x86/kvm/vmx/main.c > +++ b/arch/x86/kvm/vmx/main.c > @@ -6,6 +6,7 @@ > #include "nested.h" > #include "pmu.h" > #include "tdx.h" > +#include "tdx_arch.h" > > static bool enable_tdx __ro_after_init; > module_param_named(tdx, enable_tdx, bool, 0444); > @@ -29,6 +30,17 @@ static bool vt_is_vm_type_supported(unsigned long type) > (enable_tdx && tdx_is_vm_type_supported(type)); > } > > +static int vt_max_vcpus(struct kvm *kvm) > +{ > + if (!kvm) > + return KVM_MAX_VCPUS; > + > + if (is_td(kvm)) > + return min3(kvm->max_vcpus, KVM_MAX_VCPUS, TDX_MAX_VCPUS); > + > + return kvm->max_vcpus; > +} > + > static __init int vt_hardware_setup(void) > { > int ret; > @@ -42,6 +54,14 @@ static __init int vt_hardware_setup(void) > return 0; > } > > +static int vt_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) > +{ > + if (is_td(kvm)) > + return tdx_vm_enable_cap(kvm, cap); > + > + return -EINVAL; > +} > + > static int vt_vm_init(struct kvm *kvm) > { > if (is_td(kvm)) > @@ -81,7 +101,9 @@ struct kvm_x86_ops vt_x86_ops __initdata = { > .has_emulated_msr = vmx_has_emulated_msr, > > .is_vm_type_supported = vt_is_vm_type_supported, > + .max_vcpus = vt_max_vcpus, > .vm_size = sizeof(struct kvm_vmx), > + .vm_enable_cap = vt_vm_enable_cap, > .vm_init = vt_vm_init, > .vm_destroy = vmx_vm_destroy, > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index d759028a698e..8b02e605cfb5 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -16,6 +16,36 @@ > offsetof(struct tdsysinfo_struct, cpuid_configs)) \ > / sizeof(struct tdx_cpuid_config)) > > +int tdx_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) > +{ > + int r; > + > + switch (cap->cap) { > + case KVM_CAP_MAX_VCPUS: { > + if (cap->flags || cap->args[0] == 0) > + return -EINVAL; > + if (cap->args[0] > KVM_MAX_VCPUS) > + return -E2BIG; > + if (cap->args[0] > TDX_MAX_VCPUS) > + return -E2BIG; > + > + mutex_lock(&kvm->lock); > + if (kvm->created_vcpus) > + r = -EBUSY; > + else { > + kvm->max_vcpus = cap->args[0]; > + r = 0; > + } > + mutex_unlock(&kvm->lock); > + break; > + } > + default: > + r = -EINVAL; > + break; > + } > + return r; > +} > + > int tdx_hardware_enable(void) > { > return tdx_cpu_enable(); > diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h > index 2210c8c1e893..3860aa351bd9 100644 > --- a/arch/x86/kvm/vmx/tdx.h > +++ b/arch/x86/kvm/vmx/tdx.h > @@ -3,6 +3,9 @@ > #define __KVM_X86_TDX_H > > #ifdef CONFIG_INTEL_TDX_HOST > + > +#include "tdx_ops.h" > + > struct kvm_tdx { > struct kvm kvm; > /* TDX specific members follow. */ > diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h > index c70749114e9e..8118647aa8ca 100644 > --- a/arch/x86/kvm/vmx/x86_ops.h > +++ b/arch/x86/kvm/vmx/x86_ops.h > @@ -143,6 +143,7 @@ int tdx_hardware_enable(void); > bool tdx_is_vm_type_supported(unsigned long type); > int tdx_dev_ioctl(void __user *argp); > > +int tdx_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap); > int tdx_vm_ioctl(struct kvm *kvm, void __user *argp); > #else > static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -ENOSYS; } > @@ -150,6 +151,7 @@ static inline int tdx_hardware_enable(void) { return -EOPNOTSUPP; } > static inline bool tdx_is_vm_type_supported(unsigned long type) { return false; } > static inline int tdx_dev_ioctl(void __user *argp) { return -EOPNOTSUPP; }; > > +static inline int tdx_vm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) { return -EINVAL; }; > static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOPNOTSUPP; } > #endif > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 8687623929c3..7b02dd40ef21 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4500,6 +4500,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > break; > case KVM_CAP_MAX_VCPUS: > r = KVM_MAX_VCPUS; > + if (kvm_x86_ops.max_vcpus) > + r = static_call(kvm_x86_max_vcpus)(kvm); > break; > case KVM_CAP_MAX_VCPU_ID: > r = KVM_MAX_VCPU_IDS; > @@ -6439,6 +6441,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > break; > default: > r = -EINVAL; > + if (kvm_x86_ops.vm_enable_cap) > + r = static_call(kvm_x86_vm_enable_cap)(kvm, cap); > break; > } > return r;