[PATCH 5/5] KVM: s390: Add support for channel I/O instructions.

Cornelia Huck
2012-10-31T16:24:38Z

Add a new capability, KVM_CAP_S390_CSS_SUPPORT, which will pass
intercepts for channel I/O instructions to userspace. Only I/O
instructions interacting with I/O interrupts need to be handled
in-kernel:

- TEST PENDING INTERRUPTION (tpi) dequeues and stores pending
interrupts entirely in-kernel.
- TEST SUBCHANNEL (tsch) dequeues pending interrupts in-kernel
and exits via KVM_EXIT_S390_TSCH to userspace for subchannel-
related processing.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
Documentation/virtual/kvm/api.txt | 30 ++++++++++++
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/kvm/intercept.c | 1 +
arch/s390/kvm/interrupt.c | 37 +++++++++++++++
arch/s390/kvm/kvm-s390.c | 12 +++++
arch/s390/kvm/kvm-s390.h | 2 +
arch/s390/kvm/priv.c | 96 +++++++++++++++++++++++++++++++++++++--
arch/s390/kvm/trace-s390.h | 20 ++++++++
include/linux/kvm.h | 11 +++++
include/trace/events/kvm.h | 2 +-
10 files changed, 207 insertions(+), 5 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index a0408cf..2233081 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2294,6 +2294,22 @@ The possible hypercalls are defined in the Power Architecture Platform
Requirements (PAPR) document available from www.power.org (free
developer registration required to access it).

+ /* KVM_EXIT_S390_TSCH */
+ struct {
+ __u16 subchannel_id;
+ __u16 subchannel_nr;
+ __u32 io_int_parm;
+ __u32 io_int_word;
+ __u32 ipb;
+ __u8 dequeued;
+ } s390_tsch;
+
+s390 specific. This exit occurs when KVM_CAP_S390_CSS_SUPPORT has been enabled
+and TEST SUBCHANNEL was intercepted. If dequeued is set, a pending I/O
+interrupt for the target subchannel has been dequeued and subchannel_id,
+subchannel_nr, io_int_parm and io_int_word contain the parameters for that
+interrupt. ipb is needed for instruction parameter decoding.
+
/* Fix the size of the union. */
char padding[256];
};
@@ -2415,3 +2431,17 @@ For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV:
where "num_sets" is the tlb_sizes[] value divided by the tlb_ways[] value.
- The tsize field of mas1 shall be set to 4K on TLB0, even though the
hardware ignores this value for TLB0.
+
+6.4 KVM_CAP_S390_CSS_SUPPORT
+
+Architectures: s390
+Parameters: none
+Returns: 0 on success; -1 on error
+
+This capability enables support for handling of channel I/O instructions.
+
+TEST PENDING INTERRUPTION and the interrupt portion of TEST SUBCHANNEL are
+handled in-kernel, while the other I/O instructions are passed to userspace.
+
+When this capability is enabled, KVM_EXIT_S390_TSCH will occur on TEST
+SUBCHANNEL intercepts.
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 773859e..091c581 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -264,6 +264,7 @@ struct kvm_arch{
debug_info_t *dbf;
struct kvm_s390_float_interrupt float_int;
struct gmap *gmap;
+ int css_support;
};

extern int sie64a(struct kvm_s390_sie_block *, u64 *);
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 754dc9e..9ab2efd 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -273,6 +273,7 @@ static const intercept_handler_t intercept_funcs[] = {
[0x0C >> 2] = handle_instruction_and_prog,
[0x10 >> 2] = handle_noop,
[0x14 >> 2] = handle_noop,
+ [0x18 >> 2] = handle_noop,
[0x1C >> 2] = kvm_s390_handle_wait,
[0x20 >> 2] = handle_validity,
[0x28 >> 2] = handle_stop,
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 6b10267..495a411 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -714,6 +714,43 @@ int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code)
return 0;
}

+struct kvm_s390_interrupt_info *kvm_s390_get_io_int(struct kvm *kvm,
+ u64 cr6, u64 schid)
+{
+ struct kvm_s390_float_interrupt *fi;
+ struct kvm_s390_interrupt_info *inti, *iter;
+
+ if ((!schid && !cr6) || (schid && cr6))
+ return NULL;
+ mutex_lock(&kvm->lock);
+ fi = &kvm->arch.float_int;
+ spin_lock(&fi->lock);
+ inti = NULL;
+ list_for_each_entry(iter, &fi->list, list) {
+ if (!is_ioint(iter->type))
+ continue;
+ if (cr6 && ((cr6 & iter->io.io_int_word) == 0))
+ continue;
+ if (schid) {
+ if (((schid & 0x00000000ffff0000) >> 16) !=
+ iter->io.subchannel_id)
+ continue;
+ if ((schid & 0x000000000000ffff) !=
+ iter->io.subchannel_nr)
+ continue;
+ }
+ inti = iter;
+ break;
+ }
+ if (inti)
+ list_del_init(&inti->list);
+ if (list_empty(&fi->list))
+ atomic_set(&fi->active, 0);
+ spin_unlock(&fi->lock);
+ mutex_unlock(&kvm->lock);
+ return inti;
+}
+
int kvm_s390_inject_vm(struct kvm *kvm,
struct kvm_s390_interrupt *s390int)
{
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c19568b..fcbb711 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -141,6 +141,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_SYNC_REGS:
case KVM_CAP_ONE_REG:
case KVM_CAP_ENABLE_CAP:
+ case KVM_CAP_S390_CSS_SUPPORT:
r = 1;
break;
case KVM_CAP_NR_VCPUS:
@@ -235,6 +236,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
if (!kvm->arch.gmap)
goto out_nogmap;
}
+
+ kvm->arch.css_support = 0;
+
return 0;
out_nogmap:
debug_unregister(kvm->arch.dbf);
@@ -657,6 +661,7 @@ rerun_vcpu:
case KVM_EXIT_INTR:
case KVM_EXIT_S390_RESET:
case KVM_EXIT_S390_UCONTROL:
+ case KVM_EXIT_S390_TSCH:
break;
default:
BUG();
@@ -817,6 +822,13 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
return -EINVAL;

switch (cap->cap) {
+ case KVM_CAP_S390_CSS_SUPPORT:
+ if (!vcpu->kvm->arch.css_support) {
+ vcpu->kvm->arch.css_support = 1;
+ trace_kvm_s390_enable_css(vcpu->kvm);
+ }
+ r = 0;
+ break;
default:
r = -EINVAL;
break;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 7f50229..14a417f 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -76,6 +76,8 @@ int kvm_s390_inject_vcpu(struct kvm_vcpu *vcpu,
struct kvm_s390_interrupt *s390int);
int kvm_s390_inject_program_int(struct kvm_vcpu *vcpu, u16 code);
int kvm_s390_inject_sigp_stop(struct kvm_vcpu *vcpu, int action);
+struct kvm_s390_interrupt_info *kvm_s390_get_io_int(struct kvm *kvm,
+ u64 cr6, u64 schid);

/* implemented in priv.c */
int kvm_s390_handle_b2(struct kvm_vcpu *vcpu);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 2aba96b..7473888 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -135,15 +135,103 @@ static int handle_skey(struct kvm_vcpu *vcpu)
return 0;
}

-static int handle_io_inst(struct kvm_vcpu *vcpu)
+static int handle_tpi(struct kvm_vcpu *vcpu)
{
- VCPU_EVENT(vcpu, 4, "%s", "I/O instruction");
- /* condition code 3 */
+ u32 ipb = vcpu->arch.sie_block->ipb;
+ u64 addr;
+ struct kvm_s390_interrupt_info *inti;
+ int cc;
+
+ addr = ipb >> 28;
+ if (addr > 0)
+ addr = vcpu->run->s.regs.gprs[addr];
+
+ addr += (ipb & 0xfff0000) >> 16;
+
+ inti = kvm_s390_get_io_int(vcpu->kvm, vcpu->run->s.regs.crs[6], 0);
+ if (inti) {
+ if (addr) {
+ /*
+ * Store the two-word I/O interruption code into the
+ * provided area.
+ */
+ put_guest_u16(vcpu, addr, inti->io.subchannel_id);
+ put_guest_u16(vcpu, addr + 2, inti->io.subchannel_nr);
+ put_guest_u32(vcpu, addr + 4, inti->io.io_int_parm);
+ } else {
+ /*
+ * Store the three-word I/O interruption code into
+ * the appropriate lowcore area.
+ */
+ put_guest_u16(vcpu, 184, inti->io.subchannel_id);
+ put_guest_u16(vcpu, 186, inti->io.subchannel_nr);
+ put_guest_u32(vcpu, 188, inti->io.io_int_parm);
+ put_guest_u32(vcpu, 192, inti->io.io_int_word);
+ }
+ cc = 1;
+ } else
+ cc = 0;
+ kfree(inti);
+ /* Set condition code and we're done. */
vcpu->arch.sie_block->gpsw.mask &= ~(3ul << 44);
- vcpu->arch.sie_block->gpsw.mask |= (3 & 3ul) << 44;
+ vcpu->arch.sie_block->gpsw.mask |= (cc & 3ul) << 44;
return 0;
}

+static int handle_tsch(struct kvm_vcpu *vcpu)
+{
+ struct kvm_s390_interrupt_info *inti;
+
+ inti = kvm_s390_get_io_int(vcpu->kvm, 0,
+ vcpu->run->s.regs.gprs[1]);
+
+ /*
+ * Prepare exit to userspace.
+ * We indicate whether we dequeued a pending I/O interrupt
+ * so that userspace can re-inject it if the instruction gets
+ * a program check. While this may re-order the pending I/O
+ * interrupts, this is no problem since the priority is kept
+ * intact.
+ */
+ vcpu->run->exit_reason = KVM_EXIT_S390_TSCH;
+ vcpu->run->s390_tsch.dequeued = !!inti;
+ if (inti) {
+ vcpu->run->s390_tsch.subchannel_id = inti->io.subchannel_id;
+ vcpu->run->s390_tsch.subchannel_nr = inti->io.subchannel_nr;
+ vcpu->run->s390_tsch.io_int_parm = inti->io.io_int_parm;
+ vcpu->run->s390_tsch.io_int_word = inti->io.io_int_word;
+ }
+ vcpu->run->s390_tsch.ipb = vcpu->arch.sie_block->ipb;
+ kfree(inti);
+ return -EREMOTE;
+}
+
+static int handle_io_inst(struct kvm_vcpu *vcpu)
+{
+ VCPU_EVENT(vcpu, 4, "%s", "I/O instruction");
+
+ if (vcpu->kvm->arch.css_support) {
+ /*
+ * Most I/O instructions will be handled by userspace.
+ * Exceptions are tpi and the interrupt portion of tsch.
+ */
+ if (vcpu->arch.sie_block->ipa == 0xb236)
+ return handle_tpi(vcpu);
+ if (vcpu->arch.sie_block->ipa == 0xb235)
+ return handle_tsch(vcpu);
+ /* Handle in userspace. */
+ return -EOPNOTSUPP;
+ } else {
+ /*
+ * Set condition code 3 to stop the guest from issueing channel
+ * I/O instructions.
+ */
+ vcpu->arch.sie_block->gpsw.mask &= ~(3ul << 44);
+ vcpu->arch.sie_block->gpsw.mask |= (3 & 3ul) << 44;
+ return 0;
+ }
+}
+
static int handle_stfl(struct kvm_vcpu *vcpu)
{
unsigned int facility_list;
diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
index 95fbc1a..13f30f5 100644
--- a/arch/s390/kvm/trace-s390.h
+++ b/arch/s390/kvm/trace-s390.h
@@ -204,6 +204,26 @@ TRACE_EVENT(kvm_s390_stop_request,
);

+/*
+ * Trace point for enabling channel I/O instruction support.
+ */
+TRACE_EVENT(kvm_s390_enable_css,
+ TP_PROTO(void *kvm),
+ TP_ARGS(kvm),
+
+ TP_STRUCT__entry(
+ __field(void *, kvm)
+ ),
+
+ TP_fast_assign(
+ __entry->kvm = kvm;
+ ),
+
+ TP_printk("enabling channel I/O support (kvm @ %p)\n",
+ __entry->kvm)
+ );
+
+
#endif /* _TRACE_KVMS390_H */

/* This part must be outside protection */
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 22859dc..72aa4a3 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -168,6 +168,7 @@ struct kvm_pit_config {
#define KVM_EXIT_PAPR_HCALL 19
#define KVM_EXIT_S390_UCONTROL 20
#define KVM_EXIT_WATCHDOG 21
+#define KVM_EXIT_S390_TSCH 22

/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -285,6 +286,15 @@ struct kvm_run {
__u64 ret;
__u64 args[9];
} papr_hcall;
+ /* KVM_EXIT_S390_TSCH */
+ struct {
+ __u16 subchannel_id;
+ __u16 subchannel_nr;
+ __u32 io_int_parm;
+ __u32 io_int_word;
+ __u32 ipb;
+ __u8 dequeued;
+ } s390_tsch;
/* Fix the size of the union. */
char padding[256];
};
@@ -641,6 +651,7 @@ struct kvm_ppc_smmu_info {
#endif
#define KVM_CAP_IRQFD_RESAMPLE 82
#define KVM_CAP_PPC_BOOKE_WATCHDOG 83
+#define KVM_CAP_S390_CSS_SUPPORT 84

#ifdef KVM_CAP_IRQ_ROUTING

diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 7ef9e75..a23f47c 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -14,7 +14,7 @@
ERSN(SHUTDOWN), ERSN(FAIL_ENTRY), ERSN(INTR), ERSN(SET_TPR), \
ERSN(TPR_ACCESS), ERSN(S390_SIEIC), ERSN(S390_RESET), ERSN(DCR),\
ERSN(NMI), ERSN(INTERNAL_ERROR), ERSN(OSI), ERSN(PAPR_HCALL), \
- ERSN(S390_UCONTROL)
+ ERSN(S390_UCONTROL), ERSN(S390_TSCH)

TRACE_EVENT(kvm_userspace_exit,
TP_PROTO(__u32 reason, int errno),
--
1.7.12.4