Re: [PATCH v7 012/102] KVM: x86: Introduce vm_type to differentiate default VMs from confidential VMs

Kai Huang
2022-06-28T02:52:47Z

On Mon, 2022-06-27 at 14:53 -0700, isaku.yamahata@intel.com wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Unlike default VMs, confidential VMs (Intel TDX and AMD SEV-ES) don't allow
> some operations (e.g., memory read/write, register state access, etc).
>
> Introduce vm_type to track the type of the VM to x86 KVM. Other arch KVMs
> already use vm_type, KVM_INIT_VM accepts vm_type, and x86 KVM callback
> vm_init accepts vm_type. So follow them. Further, a different policy can
> be made based on vm_type. Define KVM_X86_DEFAULT_VM for default VM as
> default and define KVM_X86_TDX_VM for Intel TDX VM. The wrapper function
> will be defined as "bool is_td(kvm) { return vm_type == VM_TYPE_TDX; }"
>
> Add a capability KVM_CAP_VM_TYPES to effectively allow device model,
> e.g. qemu, to query what VM types are supported by KVM. This (introduce a
> new capability and add vm_type) is chosen to align with other arch KVMs
> that have VM types already. Other arch KVMs uses different name to query
> supported vm types and there is no common name for it, so new name was
> chosen.
>
> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++++
> arch/x86/include/asm/kvm-x86-ops.h | 1 +
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/include/uapi/asm/kvm.h | 3 +++
> arch/x86/kvm/svm/svm.c | 6 ++++++
> arch/x86/kvm/vmx/main.c | 1 +
> arch/x86/kvm/vmx/tdx.h | 6 +-----
> arch/x86/kvm/vmx/vmx.c | 5 +++++
> arch/x86/kvm/vmx/x86_ops.h | 1 +
> arch/x86/kvm/x86.c | 9 ++++++++-
> include/uapi/linux/kvm.h | 1 +
> tools/arch/x86/include/uapi/asm/kvm.h | 3 +++
> tools/include/uapi/linux/kvm.h | 1 +
> 13 files changed, 54 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 9cbbfdb663b6..b9ab598883b2 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -147,10 +147,31 @@ described as 'basic' will be available.
> The new VM has no virtual cpus and no memory.
> You probably want to use 0 as machine type.
>
> +X86:
> +^^^^
> +
> +Supported vm type can be queried from KVM_CAP_VM_TYPES, which returns the
> +bitmap of supported vm types. The 1-setting of bit @n means vm type with
> +value @n is supported.

Perhaps I am missing something, but I don't understand how the below changes
(except the x86 part above) in Documentation are related to this patch.

> +
> +S390:
> +^^^^^
> +
> In order to create user controlled virtual machines on S390, check
> KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
> privileged user (CAP_SYS_ADMIN).
>
> +MIPS:
> +^^^^^
> +
> +To use hardware assisted virtualization on MIPS (VZ ASE) rather than
> +the default trap & emulate implementation (which changes the virtual
> +memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
> +flag KVM_VM_MIPS_VZ.
> +
> +ARM64:
> +^^^^^^
> +
> On arm64, the physical address size for a VM (IPA Size limit) is limited
> to 40bits by default. The limit can be configured if the host supports the
> extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 75bc44aa8d51..a97cdb203a16 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -19,6 +19,7 @@ KVM_X86_OP(hardware_disable)
> 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(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 aa11525500d3..089e0a4de926 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1141,6 +1141,7 @@ enum kvm_apicv_inhibit {
> };
>
> struct kvm_arch {
> + unsigned long vm_type;
> unsigned long n_used_mmu_pages;
> unsigned long n_requested_mmu_pages;
> unsigned long n_max_mmu_pages;
> @@ -1434,6 +1435,7 @@ struct kvm_x86_ops {
> bool (*has_emulated_msr)(struct kvm *kvm, u32 index);
> void (*vcpu_after_set_cpuid)(struct kvm_vcpu *vcpu);
>
> + bool (*is_vm_type_supported)(unsigned long vm_type);
> unsigned int vm_size;
> int (*vm_init)(struct kvm *kvm);
> void (*vm_destroy)(struct kvm *kvm);
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 50a4e787d5e6..9792ec1cc317 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -531,4 +531,7 @@ struct kvm_pmu_event_filter {
> #define KVM_VCPU_TSC_CTRL 0 /* control group for the timestamp counter (TSC) */
> #define KVM_VCPU_TSC_OFFSET 0 /* attribute for the TSC offset */
>
> +#define KVM_X86_DEFAULT_VM 0
> +#define KVM_X86_TDX_VM 1
> +
> #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 247c0ad458a0..815a07c594f1 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4685,6 +4685,11 @@ static void svm_vm_destroy(struct kvm *kvm)
> sev_vm_destroy(kvm);
> }
>
> +static bool svm_is_vm_type_supported(unsigned long type)
> +{
> + return type == KVM_X86_DEFAULT_VM;
> +}
> +
> static int svm_vm_init(struct kvm *kvm)
> {
> if (!pause_filter_count || !pause_filter_thresh)
> @@ -4712,6 +4717,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> .vcpu_free = svm_vcpu_free,
> .vcpu_reset = svm_vcpu_reset,
>
> + .is_vm_type_supported = svm_is_vm_type_supported,
> .vm_size = sizeof(struct kvm_svm),
> .vm_init = svm_vm_init,
> .vm_destroy = svm_vm_destroy,
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index ac788af17d92..7be4941e4c4d 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -43,6 +43,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> .hardware_disable = vmx_hardware_disable,
> .has_emulated_msr = vmx_has_emulated_msr,
>
> + .is_vm_type_supported = vmx_is_vm_type_supported,
> .vm_size = sizeof(struct kvm_vmx),
> .vm_init = vmx_vm_init,
> .vm_destroy = vmx_vm_destroy,
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 54d7a26ed9ee..2f43db5bbefb 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -17,11 +17,7 @@ struct vcpu_tdx {
>
> static inline bool is_td(struct kvm *kvm)
> {
> - /*
> - * TDX VM type isn't defined yet.
> - * return kvm->arch.vm_type == KVM_X86_TDX_VM;
> - */
> - return false;
> + return kvm->arch.vm_type == KVM_X86_TDX_VM;
> }

If you put this patch before patch:

[PATCH v7 009/102] KVM: TDX: Add placeholders for TDX VM/vcpu structure

Then you don't need to introduce this chunk in above patch and then remove it
here, which is unnecessary and ugly.

And you can even only introduce KVM_X86_DEFAULT_VM but not KVM_X86_TDX_VM in
this patch, so you can make this patch as a infrastructural patch to report VM
type. The KVM_X86_TDX_VM can come with the patch where is_td() is introduced
(in your above patch 9).

To me, it's more clean way to write patch. For instance, this infrastructural
patch can be theoretically used by other series if they have similar thing to
support, but doesn't need to carry is_td() and KVM_X86_TDX_VM burden that you
made.

>
> static inline bool is_td_vcpu(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index b30d73d28e75..5ba62f8b42ce 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7281,6 +7281,11 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
> return err;
> }
>
> +bool vmx_is_vm_type_supported(unsigned long type)
> +{
> + return type == KVM_X86_DEFAULT_VM;
> +}
> +
> #define L1TF_MSG_SMT "L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.\n"
> #define L1TF_MSG_L1D "L1TF CPU bug present and virtualization mitigation disabled, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details.\n"
>
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 2abead2f60f7..a5e85eb4e183 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -25,6 +25,7 @@ void vmx_hardware_unsetup(void);
> int vmx_check_processor_compatibility(void);
> int vmx_hardware_enable(void);
> void vmx_hardware_disable(void);
> +bool vmx_is_vm_type_supported(unsigned long type);
> int vmx_vm_init(struct kvm *kvm);
> void vmx_vm_destroy(struct kvm *kvm);
> int vmx_vcpu_precreate(struct kvm *kvm);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fb7a33fbc136..96dc8f52a137 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4408,6 +4408,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_X86_NOTIFY_VMEXIT:
> r = kvm_caps.has_notify_vmexit;
> break;
> + case KVM_CAP_VM_TYPES:
> + r = BIT(KVM_X86_DEFAULT_VM);
> + if (static_call(kvm_x86_is_vm_type_supported)(KVM_X86_TDX_VM))
> + r |= BIT(KVM_X86_TDX_VM);
> + break;
> default:
> break;
> }
> @@ -11858,9 +11863,11 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> int ret;
> unsigned long flags;
>
> - if (type)
> + if (!static_call(kvm_x86_is_vm_type_supported)(type))
> return -EINVAL;
>
> + kvm->arch.vm_type = type;
> +
> ret = kvm_page_track_init(kvm);
> if (ret)
> goto out;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 7569b4ec199c..6d6785d2685f 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1166,6 +1166,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_S390_PROTECTED_DUMP 217
> #define KVM_CAP_X86_TRIPLE_FAULT_EVENT 218
> #define KVM_CAP_X86_NOTIFY_VMEXIT 219
> +#define KVM_CAP_VM_TYPES 220
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/tools/arch/x86/include/uapi/asm/kvm.h b/tools/arch/x86/include/uapi/asm/kvm.h
> index bf6e96011dfe..71a5851475e7 100644
> --- a/tools/arch/x86/include/uapi/asm/kvm.h
> +++ b/tools/arch/x86/include/uapi/asm/kvm.h
> @@ -525,4 +525,7 @@ struct kvm_pmu_event_filter {
> #define KVM_VCPU_TSC_CTRL 0 /* control group for the timestamp counter (TSC) */
> #define KVM_VCPU_TSC_OFFSET 0 /* attribute for the TSC offset */
>
> +#define KVM_X86_DEFAULT_VM 0
> +#define KVM_X86_TDX_VM 1
> +
> #endif /* _ASM_X86_KVM_H */
> diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
> index 6a184d260c7f..1e89b967e050 100644
> --- a/tools/include/uapi/linux/kvm.h
> +++ b/tools/include/uapi/linux/kvm.h
> @@ -1152,6 +1152,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_DISABLE_QUIRKS2 213
> /* #define KVM_CAP_VM_TSC_CONTROL 214 */
> #define KVM_CAP_SYSTEM_EVENT_DATA 215
> +#define KVM_CAP_VM_TYPES 220
>
> #ifdef KVM_CAP_IRQ_ROUTING
>

--
Thanks,
-Kai