[PATCH 01/12] KVM: s390: reverse bit ordering of irqs in pending mask

Christian Borntraeger
2018-01-16T20:02:06Z

From: Michael Mueller <mimu@linux.vnet.ibm.com>

This patch prepares a simplification of bit operations between the irq
pending mask for emulated interrupts and the Interruption Pending Mask
(IPM) which is part of the Guest Interruption State Area (GISA), a feature
that allows interrupt delivery to guests by means of the SIE instruction.

Without that change, a bit-wise *or* operation on parts of these two masks
would either require a look-up table of size 256 bytes to map the IPM
to the emulated irq pending mask bit orientation (all bits mirrored at half
byte) or a sequence of up to 8 condidional branches to perform tests of
single bit positions. Both options are to reject either by performance or
space utilization reasons.

Beyond that this change will be transparent.

Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
arch/s390/include/asm/kvm_host.h | 54 ++++++++++++++++++++--------------------
arch/s390/kvm/interrupt.c | 10 ++++----
2 files changed, 32 insertions(+), 32 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index e16a9f2a44ad..9981721f258f 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -409,35 +409,35 @@ struct kvm_vcpu_stat {
#define PGM_PER 0x80
#define PGM_CRYPTO_OPERATION 0x119

-/* irq types in order of priority */
+/* irq types in ascend order of priorities */
enum irq_types {
- IRQ_PEND_MCHK_EX = 0,
- IRQ_PEND_SVC,
- IRQ_PEND_PROG,
- IRQ_PEND_MCHK_REP,
- IRQ_PEND_EXT_IRQ_KEY,
- IRQ_PEND_EXT_MALFUNC,
- IRQ_PEND_EXT_EMERGENCY,
- IRQ_PEND_EXT_EXTERNAL,
- IRQ_PEND_EXT_CLOCK_COMP,
- IRQ_PEND_EXT_CPU_TIMER,
- IRQ_PEND_EXT_TIMING,
- IRQ_PEND_EXT_SERVICE,
- IRQ_PEND_EXT_HOST,
- IRQ_PEND_PFAULT_INIT,
- IRQ_PEND_PFAULT_DONE,
- IRQ_PEND_VIRTIO,
- IRQ_PEND_IO_ISC_0,
- IRQ_PEND_IO_ISC_1,
- IRQ_PEND_IO_ISC_2,
- IRQ_PEND_IO_ISC_3,
- IRQ_PEND_IO_ISC_4,
- IRQ_PEND_IO_ISC_5,
- IRQ_PEND_IO_ISC_6,
- IRQ_PEND_IO_ISC_7,
- IRQ_PEND_SIGP_STOP,
+ IRQ_PEND_SET_PREFIX = 0,
IRQ_PEND_RESTART,
- IRQ_PEND_SET_PREFIX,
+ IRQ_PEND_SIGP_STOP,
+ IRQ_PEND_IO_ISC_7,
+ IRQ_PEND_IO_ISC_6,
+ IRQ_PEND_IO_ISC_5,
+ IRQ_PEND_IO_ISC_4,
+ IRQ_PEND_IO_ISC_3,
+ IRQ_PEND_IO_ISC_2,
+ IRQ_PEND_IO_ISC_1,
+ IRQ_PEND_IO_ISC_0,
+ IRQ_PEND_VIRTIO,
+ IRQ_PEND_PFAULT_DONE,
+ IRQ_PEND_PFAULT_INIT,
+ IRQ_PEND_EXT_HOST,
+ IRQ_PEND_EXT_SERVICE,
+ IRQ_PEND_EXT_TIMING,
+ IRQ_PEND_EXT_CPU_TIMER,
+ IRQ_PEND_EXT_CLOCK_COMP,
+ IRQ_PEND_EXT_EXTERNAL,
+ IRQ_PEND_EXT_EMERGENCY,
+ IRQ_PEND_EXT_MALFUNC,
+ IRQ_PEND_EXT_IRQ_KEY,
+ IRQ_PEND_MCHK_REP,
+ IRQ_PEND_PROG,
+ IRQ_PEND_SVC,
+ IRQ_PEND_MCHK_EX,
IRQ_PEND_COUNT
};

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index f8eb2cfa763a..b94173560dcf 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -189,8 +189,8 @@ static int cpu_timer_irq_pending(struct kvm_vcpu *vcpu)

static inline int is_ioirq(unsigned long irq_type)
{
- return ((irq_type >= IRQ_PEND_IO_ISC_0) &&
- (irq_type <= IRQ_PEND_IO_ISC_7));
+ return ((irq_type >= IRQ_PEND_IO_ISC_7) &&
+ (irq_type <= IRQ_PEND_IO_ISC_0));
}

static uint64_t isc_to_isc_bits(int isc)
@@ -211,12 +211,12 @@ static inline unsigned long pending_irqs(struct kvm_vcpu *vcpu)

static inline int isc_to_irq_type(unsigned long isc)
{
- return IRQ_PEND_IO_ISC_0 + isc;
+ return IRQ_PEND_IO_ISC_0 - isc;
}

static inline int irq_type_to_isc(unsigned long irq_type)
{
- return irq_type - IRQ_PEND_IO_ISC_0;
+ return IRQ_PEND_IO_ISC_0 - irq_type;
}

static unsigned long disable_iscs(struct kvm_vcpu *vcpu,
@@ -1155,7 +1155,7 @@ int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)

while ((irqs = deliverable_irqs(vcpu)) && !rc) {
/* bits are in the order of interrupt priority */
- irq_type = find_first_bit(&irqs, IRQ_PEND_COUNT);
+ irq_type = find_last_bit(&irqs, IRQ_PEND_COUNT);
if (is_ioirq(irq_type)) {
rc = __deliver_io(vcpu, irq_type);
} else {
--
2.13.4