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From:
Alexander Bluhm <bluhm@openbsd.org>
Subject:
Re: vmm(4) AMD SEV
To:
Hans-J?rg H?xer <Hans-Joerg_Hoexer@genua.de>
Cc:
Dave Voutila <dv@sisu.io>, tech@openbsd.org
Date:
Mon, 26 Aug 2024 16:13:46 +0200

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On Mon, Aug 26, 2024 at 10:55:02AM +0200, Hans-J?rg H?xer wrote:
> Updated diff below.

I have repeated my tests with this diff, still running fine.

ok?

bluhm

> -----------------------------------------------------------------
> commit 659582f61af2e7b9fe67e83436d5bcae0295f7d8
> Author: Hans-Joerg Hoexer <hshoexer@genua.de>
> Date:   Thu Jul 11 16:23:00 2024 +0200
> 
>     vmm(4): SEV support
>     
>     This changes enables SEV support in vmm(4):
>     
>     - emulate cpuid 0x8000001f so the guest can discover SEV features
>     - allow vmd(8) to enable SEV on VM creation
>     - inform vmd(8) about the c-bit position and ASID assigned to each VCPU
> 
> diff --git a/sys/arch/amd64/amd64/identcpu.c b/sys/arch/amd64/amd64/identcpu.c
> index a6e31e50255..91d267fff64 100644
> --- a/sys/arch/amd64/amd64/identcpu.c
> +++ b/sys/arch/amd64/amd64/identcpu.c
> @@ -66,7 +66,7 @@ char cpu_model[48];
>  int cpuspeed;
>  
>  int amd64_has_xcrypt;
> -int amd64_pos_cbit;
> +int amd64_pos_cbit;	/* C bit position for SEV */
>  int has_rdrand;
>  int has_rdseed;
>  
> diff --git a/sys/arch/amd64/amd64/vmm_machdep.c b/sys/arch/amd64/amd64/vmm_machdep.c
> index 0df3d8b070f..eb6e9258366 100644
> --- a/sys/arch/amd64/amd64/vmm_machdep.c
> +++ b/sys/arch/amd64/amd64/vmm_machdep.c
> @@ -82,9 +82,9 @@ int vcpu_reset_regs(struct vcpu *, struct vcpu_reg_state *);
>  int vcpu_reset_regs_vmx(struct vcpu *, struct vcpu_reg_state *);
>  int vcpu_reset_regs_svm(struct vcpu *, struct vcpu_reg_state *);
>  int vcpu_reload_vmcs_vmx(struct vcpu *);
> -int vcpu_init(struct vcpu *);
> +int vcpu_init(struct vcpu *, struct vm_create_params *);
>  int vcpu_init_vmx(struct vcpu *);
> -int vcpu_init_svm(struct vcpu *);
> +int vcpu_init_svm(struct vcpu *, struct vm_create_params *);
>  int vcpu_run_vmx(struct vcpu *, struct vm_run_params *);
>  int vcpu_run_svm(struct vcpu *, struct vm_run_params *);
>  void vcpu_deinit(struct vcpu *);
> @@ -1890,7 +1890,6 @@ vcpu_reset_regs_svm(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>  {
>  	struct vmcb *vmcb;
>  	int ret;
> -	uint16_t asid;
>  
>  	vmcb = (struct vmcb *)vcpu->vc_control_va;
>  
> @@ -1963,14 +1962,7 @@ vcpu_reset_regs_svm(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>  	svm_setmsrbr(vcpu, MSR_PSTATEDEF(0));
>  
>  	/* Guest VCPU ASID */
> -	if (vmm_alloc_vpid(&asid)) {
> -		DPRINTF("%s: could not allocate asid\n", __func__);
> -		ret = EINVAL;
> -		goto exit;
> -	}
> -
> -	vmcb->v_asid = asid;
> -	vcpu->vc_vpid = asid;
> +	vmcb->v_asid = vcpu->vc_vpid;
>  
>  	/* TLB Control - First time in, flush all*/
>  	vmcb->v_tlb_control = SVM_TLB_CONTROL_FLUSH_ALL;
> @@ -1985,9 +1977,13 @@ vcpu_reset_regs_svm(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>              PATENTRY(6, PAT_UCMINUS) | PATENTRY(7, PAT_UC);
>  
>  	/* NPT */
> -	vmcb->v_np_enable = 1;
> +	vmcb->v_np_enable = SVM_ENABLE_NP;
>  	vmcb->v_n_cr3 = vcpu->vc_parent->vm_map->pmap->pm_pdirpa;
>  
> +	/* SEV */
> +	if (vcpu->vc_sev)
> +		vmcb->v_np_enable |= SVM_ENABLE_SEV;
> +
>  	/* Enable SVME in EFER (must always be set) */
>  	vmcb->v_efer |= EFER_SVME;
>  
> @@ -1998,7 +1994,6 @@ vcpu_reset_regs_svm(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>  
>  	vcpu->vc_parent->vm_map->pmap->eptp = 0;
>  
> -exit:
>  	return ret;
>  }
>  
> @@ -3086,6 +3081,7 @@ vcpu_reset_regs(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>   *
>   * Parameters:
>   *  vcpu: the VCPU structure being initialized
> + *  vcp: parameters provided by vmd(8)
>   *
>   * Return values:
>   *  0: the VCPU was initialized successfully
> @@ -3093,8 +3089,9 @@ vcpu_reset_regs(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
>   *  EINVAL: an error occurred during VCPU initialization
>   */
>  int
> -vcpu_init_svm(struct vcpu *vcpu)
> +vcpu_init_svm(struct vcpu *vcpu, struct vm_create_params *vcp)
>  {
> +	uint16_t asid;
>  	int ret = 0;
>  
>  	/* Allocate VMCB VA */
> @@ -3176,6 +3173,21 @@ vcpu_init_svm(struct vcpu *vcpu)
>  	    (uint64_t)vcpu->vc_svm_ioio_va,
>  	    (uint64_t)vcpu->vc_svm_ioio_pa);
>  
> +	/* Guest VCPU ASID */
> +	if (vmm_alloc_vpid(&asid)) {
> +		DPRINTF("%s: could not allocate asid\n", __func__);
> +		ret = EINVAL;
> +		goto exit;
> +	}
> +	vcpu->vc_vpid = asid;
> +
> +	/* Shall we enable SEV? */
> +	vcpu->vc_sev = vcp->vcp_sev;
> +
> +	/* Inform vmd(8) about ASID and C bit position. */
> +	vcp->vcp_poscbit = amd64_pos_cbit;
> +	vcp->vcp_asid[vcpu->vc_id] = vcpu->vc_vpid;
> +
>  exit:
>  	if (ret)
>  		vcpu_deinit_svm(vcpu);
> @@ -3189,7 +3201,7 @@ exit:
>   * Calls the architecture-specific VCPU init routine
>   */
>  int
> -vcpu_init(struct vcpu *vcpu)
> +vcpu_init(struct vcpu *vcpu, struct vm_create_params *vcp)
>  {
>  	int ret = 0;
>  
> @@ -3207,7 +3219,7 @@ vcpu_init(struct vcpu *vcpu)
>  	if (vmm_softc->mode == VMM_MODE_EPT)
>  		ret = vcpu_init_vmx(vcpu);
>  	else if (vmm_softc->mode == VMM_MODE_RVI)
> -		ret = vcpu_init_svm(vcpu);
> +		ret = vcpu_init_svm(vcpu, vcp);
>  	else
>  		panic("%s: unknown vmm mode: %d", __func__, vmm_softc->mode);
>  
> @@ -6285,7 +6297,7 @@ vmm_handle_cpuid(struct vcpu *vcpu)
>  		*rdx = 0;
>  		break;
>  	case 0x80000000:	/* Extended function level */
> -		*rax = 0x80000008; /* curcpu()->ci_pnfeatset */
> +		*rax = 0x8000001f; /* curcpu()->ci_pnfeatset */
>  		*rbx = 0;
>  		*rcx = 0;
>  		*rdx = 0;
> @@ -6345,6 +6357,12 @@ vmm_handle_cpuid(struct vcpu *vcpu)
>  		*rcx = ecx;
>  		*rdx = edx;
>  		break;
> +	case 0x8000001f:	/* encryption features (AMD) */
> +		*rax = eax;
> +		*rbx = ebx;
> +		*rcx = ecx;
> +		*rdx = edx;
> +		break;
>  	default:
>  		DPRINTF("%s: unsupported rax=0x%llx\n", __func__, *rax);
>  		*rax = 0;
> diff --git a/sys/arch/amd64/include/cpu.h b/sys/arch/amd64/include/cpu.h
> index f5aada4d4d3..67cef9c37b8 100644
> --- a/sys/arch/amd64/include/cpu.h
> +++ b/sys/arch/amd64/include/cpu.h
> @@ -415,6 +415,7 @@ void	x86_print_cacheinfo(struct cpu_info *);
>  void	identifycpu(struct cpu_info *);
>  int	cpu_amd64speed(int *);
>  extern int cpuspeed;
> +extern int amd64_pos_cbit;
>  
>  /* machdep.c */
>  void	dumpconf(void);
> diff --git a/sys/arch/amd64/include/vmmvar.h b/sys/arch/amd64/include/vmmvar.h
> index 3f35e520926..855855ad2a7 100644
> --- a/sys/arch/amd64/include/vmmvar.h
> +++ b/sys/arch/amd64/include/vmmvar.h
> @@ -624,6 +624,7 @@ enum {
>  
>  /* Forward declarations */
>  struct vm;
> +struct vm_create_params;
>  
>  /*
>   * Implementation-specific cpu state
> @@ -636,6 +637,9 @@ struct vmcb_segment {
>  	uint64_t			vs_base;		/* 008h */
>  };
>  
> +#define SVM_ENABLE_NP	(1ULL << 0)
> +#define SVM_ENABLE_SEV	(1ULL << 1)
> +
>  struct vmcb {
>  	union {
>  		struct {
> @@ -893,6 +897,7 @@ struct vcpu {
>  	paddr_t vc_svm_hsa_pa;
>  	vaddr_t vc_svm_ioio_va;
>  	paddr_t vc_svm_ioio_pa;
> +	int vc_sev;				/* [I] */
>  };
>  
>  SLIST_HEAD(vcpu_head, vcpu);
> @@ -921,7 +926,7 @@ int	vmm_start(void);
>  int	vmm_stop(void);
>  int	vm_impl_init(struct vm *, struct proc *);
>  void	vm_impl_deinit(struct vm *);
> -int	vcpu_init(struct vcpu *);
> +int	vcpu_init(struct vcpu *, struct vm_create_params *);
>  void	vcpu_deinit(struct vcpu *);
>  int	vm_rwregs(struct vm_rwregs_params *, int);
>  int	vcpu_reset_regs(struct vcpu *, struct vcpu_reg_state *);
> diff --git a/sys/dev/vmm/vmm.c b/sys/dev/vmm/vmm.c
> index 4d4866f70dc..35c00943302 100644
> --- a/sys/dev/vmm/vmm.c
> +++ b/sys/dev/vmm/vmm.c
> @@ -399,13 +399,13 @@ vm_create(struct vm_create_params *vcp, struct proc *p)
>  		vcpu = pool_get(&vcpu_pool, PR_WAITOK | PR_ZERO);
>  
>  		vcpu->vc_parent = vm;
> -		if ((ret = vcpu_init(vcpu)) != 0) {
> +		vcpu->vc_id = vm->vm_vcpu_ct;
> +		vm->vm_vcpu_ct++;
> +		if ((ret = vcpu_init(vcpu, vcp)) != 0) {
>  			printf("failed to init vcpu %d for vm %p\n", i, vm);
>  			vm_teardown(&vm);
>  			return (ret);
>  		}
> -		vcpu->vc_id = vm->vm_vcpu_ct;
> -		vm->vm_vcpu_ct++;
>  		/* Publish vcpu to list, inheriting the reference. */
>  		SLIST_INSERT_HEAD(&vm->vm_vcpu_list, vcpu, vc_vcpu_link);
>  	}
> diff --git a/sys/dev/vmm/vmm.h b/sys/dev/vmm/vmm.h
> index ac682bc2c45..677885c8fc0 100644
> --- a/sys/dev/vmm/vmm.h
> +++ b/sys/dev/vmm/vmm.h
> @@ -49,9 +49,12 @@ struct vm_create_params {
>  	size_t			vcp_ncpus;
>  	struct vm_mem_range	vcp_memranges[VMM_MAX_MEM_RANGES];
>  	char			vcp_name[VMM_MAX_NAME_LEN];
> +	int			vcp_sev;
>  
>          /* Output parameter from VMM_IOC_CREATE */
>          uint32_t		vcp_id;
> +        uint32_t		vcp_poscbit;
> +        uint32_t		vcp_asid[VMM_MAX_VCPUS];
>  };
>  
>  struct vm_info_result {