Re: [PATCH v10 017/108] KVM: TDX: Refuse to unplug the last cpu on the package

Binbin Wu
2022-11-02T08:06:31Z

On 2022/10/30 14:22, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> In order to reclaim TDX host key id, (i.e. when deleting guest TD), needs
> to call TDH.PHYMEM.PAGE.WBINVD on all packages. If we have used TDX host
> key id, refuse to offline the last online cpu.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/include/asm/kvm-x86-ops.h | 1 +
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/vmx/main.c | 1 +
> arch/x86/kvm/vmx/tdx.c | 40 +++++++++++++++++++++++++++++-
> arch/x86/kvm/vmx/x86_ops.h | 2 ++
> arch/x86/kvm/x86.c | 27 ++++++++++++--------
> 6 files changed, 61 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 3a29a6b31ee8..0ceb8e58a6c0 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -17,6 +17,7 @@ BUILD_BUG_ON(1)
> KVM_X86_OP(hardware_enable)
> KVM_X86_OP(hardware_disable)
> KVM_X86_OP(hardware_unsetup)
> +KVM_X86_OP_OPTIONAL_RET0(offline_cpu)
> KVM_X86_OP(has_emulated_msr)
> KVM_X86_OP(vcpu_after_set_cpuid)
> KVM_X86_OP(is_vm_type_supported)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 2870155ce6fb..50b39d0071ff 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1466,6 +1466,7 @@ struct kvm_x86_ops {
> int (*hardware_enable)(void);
> void (*hardware_disable)(void);
> void (*hardware_unsetup)(void);
> + int (*offline_cpu)(void);
> bool (*has_emulated_msr)(struct kvm *kvm, u32 index);
> void (*vcpu_after_set_cpuid)(struct kvm_vcpu *vcpu);
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index d01a946a18cf..0918d1e6d2f3 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -67,6 +67,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> .name = "kvm_intel",
>
> .hardware_unsetup = vt_hardware_unsetup,
> + .offline_cpu = tdx_offline_cpu,
> .check_processor_compatibility = vmx_check_processor_compatibility,
>
> .hardware_enable = vmx_hardware_enable,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index ec88dde0d300..64229c3b3c5a 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -42,6 +42,7 @@ static struct tdx_capabilities tdx_caps;
> */
> static DEFINE_MUTEX(tdx_lock);
> static struct mutex *tdx_mng_key_config_lock;
> +static atomic_t nr_configured_hkid;
>
> static __always_inline hpa_t set_hkid_to_hpa(hpa_t pa, u16 hkid)
> {
> @@ -222,7 +223,8 @@ void tdx_mmu_release_hkid(struct kvm *kvm)
> pr_err("tdh_mng_key_freeid failed. HKID %d is leaked.\n",
> kvm_tdx->hkid);
> return;
> - }
> + } else
> + atomic_dec(&nr_configured_hkid);
>
> free_hkid:
> tdx_hkid_free(kvm_tdx);
> @@ -371,6 +373,8 @@ int tdx_vm_init(struct kvm *kvm)
> if (ret)
> break;
> }
> + if (!ret)
> + atomic_inc(&nr_configured_hkid);
> cpus_read_unlock();
> free_cpumask_var(packages);
> if (ret)
> @@ -514,3 +518,37 @@ void tdx_hardware_unsetup(void)
> /* kfree accepts NULL. */
> kfree(tdx_mng_key_config_lock);
> }
> +
> +int tdx_offline_cpu(void)
> +{
> + int curr_cpu = smp_processor_id();
> + cpumask_var_t packages;
> + int ret = 0;
> + int i;
> +
> + if (!atomic_read(&nr_configured_hkid))
> + return 0;
> +
> + /*
> + * To reclaim hkid, need to call TDH.PHYMEM.PAGE.WBINVD on all packages.
> + * If this is the last online cpu on the package, refuse offline.
> + */
> + if (!zalloc_cpumask_var(&packages, GFP_KERNEL))
> + return -ENOMEM;
> +
> + for_each_online_cpu(i) {
> + if (i != curr_cpu)
> + cpumask_set_cpu(topology_physical_package_id(i), packages);
> + }
> + if (!cpumask_test_cpu(topology_physical_package_id(curr_cpu), packages))
> + ret = -EBUSY;
> + free_cpumask_var(packages);
> + if (ret)
> + /*
> + * Because it's hard for human operator to understand the
> + * reason, warn it.
> + */
> + pr_warn("TDX requires all packages to have an online CPU. "
> + "Delete all TDs in order to offline all CPUs of a package.\n");
> + return ret;
> +}
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 95da978c9aa9..b2cb5786830a 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -134,6 +134,7 @@ void vmx_setup_mce(struct kvm_vcpu *vcpu);
> int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops);
> bool tdx_is_vm_type_supported(unsigned long type);
> void tdx_hardware_unsetup(void);
> +int tdx_offline_cpu(void);
>
> int tdx_vm_init(struct kvm *kvm);
> void tdx_mmu_release_hkid(struct kvm *kvm);
> @@ -142,6 +143,7 @@ void tdx_vm_free(struct kvm *kvm);
> static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return 0; }
> static inline bool tdx_is_vm_type_supported(unsigned long type) { return false; }
> static inline void tdx_hardware_unsetup(void) {}
> +static inline int tdx_offline_cpu(void) { return 0; }
>
> static inline int tdx_vm_init(struct kvm *kvm) { return -EOPNOTSUPP; }
> static inline void tdx_mmu_release_hkid(struct kvm *kvm) {}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4b22196cb12c..25c30c8c2d9b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12337,16 +12337,23 @@ int kvm_arch_online_cpu(unsigned int cpu, int usage_count)
>
> int kvm_arch_offline_cpu(unsigned int cpu, int usage_count)
> {
> - if (usage_count) {
> - /*
> - * arch callback kvm_arch_hardware_disable() assumes that
> - * preemption is disabled for historical reason. Disable
> - * preemption until all arch callbacks are fixed.
> - */
> - preempt_disable();
> - hardware_disable(NULL);
> - preempt_enable();
> - }
> + int ret;
> +
> + if (!usage_count)
> + return 0;
> +
> + ret = static_call(kvm_x86_offline_cpu)();

Use static_call_cond instead?
Seems the new interface for x86 is only implemented for Intel.

> + if (ret)
> + return ret;
> +
> + /*
> + * arch callback kvm_arch_hardware_disable() assumes that preemption is
> + * disabled for historical reason. Disable preemption until all arch
> + * callbacks are fixed.
> + */
> + preempt_disable();
> + hardware_disable(NULL);
> + preempt_enable();
> return 0;
> }
>