Commit 8e8678e7 authored by Janosch Frank's avatar Janosch Frank
Browse files

KVM: s390: Add capability that forwards operation exceptions 



Setting KVM_CAP_S390_USER_OPEREXEC will forward all operation
exceptions to user space. This also includes the 0x0000 instructions
managed by KVM_CAP_S390_USER_INSTR0. It's helpful if user space wants
to emulate instructions which do not (yet) have an opcode.

While we're at it refine the documentation for
KVM_CAP_S390_USER_INSTR0.

Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Reviewed-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: default avatarChristian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
parent 182a258b

Documentation/virt/kvm/api.rst

+16 −1
Original line number Diff line number Diff line
@@ -7820,7 +7820,7 @@ where 0xff represents CPUs 0-7 in cluster 0. 
:Architectures: s390

:Parameters: none



With this capability enabled, all illegal instructions 0x0000 (2 bytes) will

With this capability enabled, the illegal instruction 0x0000 (2 bytes) will

be intercepted and forwarded to user space. User space can use this

mechanism e.g. to realize 2-byte software breakpoints. The kernel will

not inject an operating exception for these instructions, user space has
@@ -8703,6 +8703,21 @@ This capability indicate to the userspace whether a PFNMAP memory region 
can be safely mapped as cacheable. This relies on the presence of

force write back (FWB) feature support on the hardware.



7.45 KVM_CAP_S390_USER_OPEREXEC

-------------------------------



:Architectures: s390

:Parameters: none



When this capability is enabled KVM forwards all operation exceptions

that it doesn't handle itself to user space. This also includes the

0x0000 instructions managed by KVM_CAP_S390_USER_INSTR0. This is

helpful if user space wants to emulate instructions which are not

(yet) implemented in hardware.



This capability can be enabled dynamically even if VCPUs were already

created and are running.



8. Other capabilities.

======================

arch/s390/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -648,6 +648,7 @@ struct kvm_arch { 
	int user_sigp;

	int user_stsi;

	int user_instr0;

	int user_operexec;

	struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS];

	wait_queue_head_t ipte_wq;

	int ipte_lock_count;

arch/s390/kvm/intercept.c

+3 −0
Original line number Diff line number Diff line
@@ -471,6 +471,9 @@ static int handle_operexc(struct kvm_vcpu *vcpu) 
	if (vcpu->arch.sie_block->ipa == 0xb256)

		return handle_sthyi(vcpu);



	if (vcpu->kvm->arch.user_operexec)

		return -EOPNOTSUPP;



	if (vcpu->arch.sie_block->ipa == 0 && vcpu->kvm->arch.user_instr0)

		return -EOPNOTSUPP;

	rc = read_guest_lc(vcpu, __LC_PGM_NEW_PSW, &newpsw, sizeof(psw_t));

arch/s390/kvm/kvm-s390.c

+7 −0
Original line number Diff line number Diff line
@@ -606,6 +606,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) 
	case KVM_CAP_SET_GUEST_DEBUG:

	case KVM_CAP_S390_DIAG318:

	case KVM_CAP_IRQFD_RESAMPLE:

	case KVM_CAP_S390_USER_OPEREXEC:

		r = 1;

		break;

	case KVM_CAP_SET_GUEST_DEBUG2:
@@ -921,6 +922,12 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) 
		VM_EVENT(kvm, 3, "ENABLE: CAP_S390_CPU_TOPOLOGY %s",

			 r ? "(not available)" : "(success)");

		break;

	case KVM_CAP_S390_USER_OPEREXEC:

		VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_OPEREXEC");

		kvm->arch.user_operexec = 1;

		icpt_operexc_on_all_vcpus(kvm);

		r = 0;

		break;

	default:

		r = -EINVAL;

		break;

include/uapi/linux/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -963,6 +963,7 @@ struct kvm_enable_cap { 
#define KVM_CAP_RISCV_MP_STATE_RESET 242

#define KVM_CAP_ARM_CACHEABLE_PFNMAP_SUPPORTED 243

#define KVM_CAP_GUEST_MEMFD_FLAGS 244

#define KVM_CAP_S390_USER_OPEREXEC 245



struct kvm_irq_routing_irqchip {

	__u32 irqchip;