Re: [PATCH 6/7] target/i386: Implement mc->kvm_type() to get VM type

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Mar 19, 2024 at 02:59:59PM +0100, Paolo Bonzini wrote:
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> 
> KVM is introducing a new API to create confidential guests, which
> will be used by TDX and SEV-SNP but is also available for SEV and
> SEV-ES.  The API uses the VM type argument to KVM_CREATE_VM to
> identify which confidential computing technology to use.
> 
> Since there are no other expected uses of VM types, delegate
> mc->kvm_type() for x86 boards to the confidential-guest-support
> object pointed to by ms->cgs.
> 
> For example, if a sev-guest object is specified to confidential-guest-support,
> like,
> 
>   qemu -machine ...,confidential-guest-support=sev0 \
>        -object sev-guest,id=sev0,...
> 
> it will check if a VM type KVM_X86_SEV_VM or KVM_X86_SEV_ES_VM
> is supported, and if so use them together with the KVM_SEV_INIT2
> function of the KVM_MEMORY_ENCRYPT_OP ioctl. If not, it will fall back to
> KVM_SEV_INIT and KVM_SEV_ES_INIT.
> 
> This is a preparatory work towards TDX and SEV-SNP support, but it
> will also enable support for VMSA features such as DebugSwap, which
> are only available via KVM_SEV_INIT2.
> 
> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  target/i386/confidential-guest.h | 19 ++++++++++++++
>  target/i386/kvm/kvm_i386.h       |  2 ++
>  hw/i386/x86.c                    |  6 +++++
>  target/i386/kvm/kvm.c            | 44 ++++++++++++++++++++++++++++++++
>  4 files changed, 71 insertions(+)
> 
> diff --git a/target/i386/confidential-guest.h b/target/i386/confidential-guest.h
> index ca12d5a8fba..532e172a60b 100644
> --- a/target/i386/confidential-guest.h
> +++ b/target/i386/confidential-guest.h
> @@ -36,5 +36,24 @@ struct X86ConfidentialGuest {
>  struct X86ConfidentialGuestClass {
>      /* <private> */
>      ConfidentialGuestSupportClass parent;
> +
> +    /* <public> */
> +    int (*kvm_type)(X86ConfidentialGuest *cg);
>  };
> +
> +/**
> + * x86_confidential_guest_kvm_type:
> + *
> + * Calls #X86ConfidentialGuestClass.unplug callback of @plug_handler.
> + */
> +static inline int x86_confidential_guest_kvm_type(X86ConfidentialGuest *cg)
> +{
> +    X86ConfidentialGuestClass *klass = X86_CONFIDENTIAL_GUEST_GET_CLASS(cg);
> +
> +    if (klass->kvm_type) {
> +        return klass->kvm_type(cg);
> +    } else {
> +        return 0;
> +    }
> +}
>  #endif
> diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
> index 30fedcffea3..02168122787 100644
> --- a/target/i386/kvm/kvm_i386.h
> +++ b/target/i386/kvm/kvm_i386.h
> @@ -37,6 +37,7 @@ bool kvm_hv_vpindex_settable(void);
>  bool kvm_enable_sgx_provisioning(KVMState *s);
>  bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
>  
> +int kvm_get_vm_type(MachineState *ms, const char *vm_type);
>  void kvm_arch_reset_vcpu(X86CPU *cs);
>  void kvm_arch_after_reset_vcpu(X86CPU *cpu);
>  void kvm_arch_do_init_vcpu(X86CPU *cs);
> @@ -49,6 +50,7 @@ void kvm_request_xsave_components(X86CPU *cpu, uint64_t mask);
>  
>  #ifdef CONFIG_KVM
>  
> +bool kvm_is_vm_type_supported(int type);
>  bool kvm_has_adjust_clock_stable(void);
>  bool kvm_has_exception_payload(void);
>  void kvm_synchronize_all_tsc(void);
> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> index ffbda48917f..2d4b148cd25 100644
> --- a/hw/i386/x86.c
> +++ b/hw/i386/x86.c
> @@ -1389,6 +1389,11 @@ static void machine_set_sgx_epc(Object *obj, Visitor *v, const char *name,
>      qapi_free_SgxEPCList(list);
>  }
>  
> +static int x86_kvm_type(MachineState *ms, const char *vm_type)
> +{
> +    return kvm_enabled() ? kvm_get_vm_type(ms, vm_type) : 0;
> +}
> +
>  static void x86_machine_initfn(Object *obj)
>  {
>      X86MachineState *x86ms = X86_MACHINE(obj);
> @@ -1413,6 +1418,7 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
>      mc->cpu_index_to_instance_props = x86_cpu_index_to_props;
>      mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
>      mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
> +    mc->kvm_type = x86_kvm_type;
>      x86mc->save_tsc_khz = true;
>      x86mc->fwcfg_dma_enabled = true;
>      nc->nmi_monitor_handler = x86_nmi;
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index 0ec69109a2b..e109648f260 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -31,6 +31,7 @@
>  #include "sysemu/kvm_int.h"
>  #include "sysemu/runstate.h"
>  #include "kvm_i386.h"
> +#include "../confidential-guest.h"
>  #include "sev.h"
>  #include "xen-emu.h"
>  #include "hyperv.h"
> @@ -161,6 +162,49 @@ static KVMMSRHandlers msr_handlers[KVM_MSR_FILTER_MAX_RANGES];
>  static RateLimit bus_lock_ratelimit_ctrl;
>  static int kvm_get_one_msr(X86CPU *cpu, int index, uint64_t *value);
>  
> +static const char *vm_type_name[] = {
> +    [KVM_X86_DEFAULT_VM] = "default",
> +};
> +
> +bool kvm_is_vm_type_supported(int type)
> +{
> +    uint32_t machine_types;
> +
> +    /*
> +     * old KVM doesn't support KVM_CAP_VM_TYPES but KVM_X86_DEFAULT_VM
> +     * is always supported
> +     */
> +    if (type == KVM_X86_DEFAULT_VM) {
> +        return true;
> +    }
> +
> +    machine_types = kvm_check_extension(KVM_STATE(current_machine->accelerator),
> +                                        KVM_CAP_VM_TYPES);
> +    return !!(machine_types & BIT(type));
> +}
> +
> +int kvm_get_vm_type(MachineState *ms, const char *vm_type)

The 'vm_type' parameter is never used here. What value is it expected
to have, and should be diagnosing an error if some unexpected value
is provided.

> +{
> +    int kvm_type = KVM_X86_DEFAULT_VM;
> +
> +    if (ms->cgs) {
> +        if (!object_dynamic_cast(OBJECT(ms->cgs), TYPE_X86_CONFIDENTIAL_GUEST)) {
> +            error_report("configuration type %s not supported for x86 guests",
> +                         object_get_typename(OBJECT(ms->cgs)));
> +            exit(1);
> +        }
> +        kvm_type = x86_confidential_guest_kvm_type(
> +            X86_CONFIDENTIAL_GUEST(ms->cgs));
> +    }
> +
> +    if (!kvm_is_vm_type_supported(kvm_type)) {
> +        error_report("vm-type %s not supported by KVM", vm_type_name[kvm_type]);
> +        exit(1);
> +    }
> +
> +    return kvm_type;
> +}
> +
>  bool kvm_has_smm(void)
>  {
>      return kvm_vm_check_extension(kvm_state, KVM_CAP_X86_SMM);
> -- 
> 2.44.0
> 
> 

With regards,
Daniel
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