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SubjectRe: [RFC PATCH v5 003/104] KVM: TDX: Detect CPU feature on kernel module initialization
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On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> TDX requires several initialization steps for KVM to create guest TDs.
> Detect CPU feature, enable VMX (TDX is based on VMX), detect TDX module
> availability, and initialize TDX module. This patch implements the first
> step to detect CPU feature. Because VMX isn't enabled yet by VMXON
> instruction on KVM kernel module initialization, defer further
> initialization step until VMX is enabled by hardware_enable callback.
>
> Introduce a module parameter, enable_tdx, to explicitly enable TDX KVM
> support. It's off by default to keep same behavior for those who don't use
> TDX. Implement CPU feature detection at KVM kernel module initialization
> as hardware_setup callback to check if CPU feature is available and get
> some CPU parameters.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/kvm/Makefile | 1 +
> arch/x86/kvm/vmx/main.c | 15 ++++++++++-
> arch/x86/kvm/vmx/tdx.c | 53 ++++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/x86_ops.h | 6 +++++
> 4 files changed, 74 insertions(+), 1 deletion(-)
> create mode 100644 arch/x86/kvm/vmx/tdx.c
>
> diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
> index ee4d0999f20f..e2c05195cb95 100644
> --- a/arch/x86/kvm/Makefile
> +++ b/arch/x86/kvm/Makefile
> @@ -24,6 +24,7 @@ kvm-$(CONFIG_KVM_XEN) += xen.o
> kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
> vmx/evmcs.o vmx/nested.o vmx/posted_intr.o vmx/main.o
> kvm-intel-$(CONFIG_X86_SGX_KVM) += vmx/sgx.o
> +kvm-intel-$(CONFIG_INTEL_TDX_HOST) += vmx/tdx.o
>
> kvm-amd-y += svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index b08ea9c42a11..b79fcc8d81dd 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -6,6 +6,19 @@
> #include "nested.h"
> #include "pmu.h"
>
> +static __init int vt_hardware_setup(void)
> +{
> + int ret;
> +
> + ret = vmx_hardware_setup();
> + if (ret)
> + return ret;
> +
> + tdx_hardware_setup(&vt_x86_ops);
> +
> + return 0;
> +}
> +
> struct kvm_x86_ops vt_x86_ops __initdata = {
> .name = "kvm_intel",
>
> @@ -147,7 +160,7 @@ struct kvm_x86_init_ops vt_init_ops __initdata = {
> .cpu_has_kvm_support = vmx_cpu_has_kvm_support,
> .disabled_by_bios = vmx_disabled_by_bios,
> .check_processor_compatibility = vmx_check_processor_compat,
> - .hardware_setup = vmx_hardware_setup,
> + .hardware_setup = vt_hardware_setup,
> .handle_intel_pt_intr = NULL,
>
> .runtime_ops = &vt_x86_ops,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> new file mode 100644
> index 000000000000..1acf08c310c4
> --- /dev/null
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/cpu.h>
> +
> +#include <asm/tdx.h>
> +
> +#include "capabilities.h"
> +#include "x86_ops.h"
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "tdx: " fmt
> +
> +static bool __read_mostly enable_tdx = true;
> +module_param_named(tdx, enable_tdx, bool, 0644);
> +
> +static u64 hkid_mask __ro_after_init;
> +static u8 hkid_start_pos __ro_after_init;
> +
> +static int __init __tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> +{
> + u32 max_pa;
> +
> + if (!enable_ept) {
> + pr_warn("Cannot enable TDX with EPT disabled\n");
> + return -EINVAL;
> + }
> +
> + if (!platform_has_tdx()) {
> + pr_warn("Cannot enable TDX with SEAMRR disabled\n");
> + return -ENODEV;
> + }

This will cause a pr_warn in the logs on all machines that don't have
TDX. Perhaps you can restrict the pr_warn() to machines that have
__seamrr_enabled() == true?

Paolo

> + if (WARN_ON_ONCE(x86_ops->tlb_remote_flush))
> + return -EIO;
> +
> + max_pa = cpuid_eax(0x80000008) & 0xff;
> + hkid_start_pos = boot_cpu_data.x86_phys_bits;
> + hkid_mask = GENMASK_ULL(max_pa - 1, hkid_start_pos);
> +
> + return 0;
> +}
> +
> +void __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> +{
> + /*
> + * This function is called at the initialization. No need to protect
> + * enable_tdx.
> + */
> + if (!enable_tdx)
> + return;
> +
> + if (__tdx_hardware_setup(&vt_x86_ops))
> + enable_tdx = false;
> +}
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 40c64fb1f505..ccf98e79d8c3 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -123,4 +123,10 @@ void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu);
> #endif
> void vmx_setup_mce(struct kvm_vcpu *vcpu);
>
> +#ifdef CONFIG_INTEL_TDX_HOST
> +void __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops);
> +#else
> +static inline void tdx_hardware_setup(struct kvm_x86_ops *x86_ops) {}
> +#endif
> +
> #endif /* __KVM_X86_VMX_X86_OPS_H */

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