KVM: kvmtrace: Remove use of bit fields in kvm trace structure

This patch fixes kvmtrace use on big endian systems. When using bit fields the
compiler will lay data out in the wrong order expected when laid down into a
file.
This fixes it by using one variable instead of using bit fields.

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 23 insertions, 11 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 8a3ceadb1366..8a16b083df2e 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -311,9 +311,13 @@ struct kvm_s390_interrupt {
 
 /* This structure represents a single trace buffer record. */
 struct kvm_trace_rec {
-        __u32 event:28;
-        __u32 extra_u32:3;
-        __u32 cycle_in:1;
+        /* variable rec_val
+         * is split into:
+         * bits 0 - 27  -> event id
+         * bits 28 -30  -> number of extra data args of size u32
+         * bits 31      -> binary indicator for if tsc is in record
+         */
+        __u32 rec_val;
         __u32 pid;
         __u32 vcpu_id;
         union {
@@ -327,6 +331,13 @@ struct kvm_trace_rec {
         } u;
 };
 
+#define TRACE_REC_EVENT_ID(val) \
+                (0x0fffffff & (val))
+#define TRACE_REC_NUM_DATA_ARGS(val) \
+                (0x70000000 & ((val) << 28))
+#define TRACE_REC_TCS(val) \
+                (0x80000000 & ((val) << 31))
+
 #define KVMIO 0xAE
 
 /*
diff --git a/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
index 58141f31ea8f..9acb78b3cc9f 100644
--- a/virt/kvm/kvm_trace.c
+++ b/virt/kvm/kvm_trace.c
@@ -54,12 +54,13 @@ static void kvm_add_trace(void *probe_private, void *call_data,
         struct kvm_trace *kt = kvm_trace;
         struct kvm_trace_rec rec;
         struct kvm_vcpu *vcpu;
-        int    i, extra, size;
+        int    i, size;
+        u32    extra;
 
         if (unlikely(kt->trace_state != KVM_TRACE_STATE_RUNNING))
                 return;
 
-        rec.event       = va_arg(*args, u32);
+        rec.rec_val     = TRACE_REC_EVENT_ID(va_arg(*args, u32));
         vcpu            = va_arg(*args, struct kvm_vcpu *);
         rec.pid         = current->tgid;
         rec.vcpu_id     = vcpu->vcpu_id;
@@ -67,21 +68,21 @@ static void kvm_add_trace(void *probe_private, void *call_data,
         extra           = va_arg(*args, u32);
         WARN_ON(!(extra <= KVM_TRC_EXTRA_MAX));
         extra           = min_t(u32, extra, KVM_TRC_EXTRA_MAX);
-        rec.extra_u32   = extra;
 
-        rec.cycle_in    = p->cycle_in;
+        rec.rec_val |= TRACE_REC_TCS(p->cycle_in)
+                        | TRACE_REC_NUM_DATA_ARGS(extra);
 
-        if (rec.cycle_in) {
+        if (p->cycle_in) {
                 rec.u.cycle.cycle_u64 = get_cycles();
 
-                for (i = 0; i < rec.extra_u32; i++)
+                for (i = 0; i < extra; i++)
                         rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
         } else {
-                for (i = 0; i < rec.extra_u32; i++)
+                for (i = 0; i < extra; i++)
                         rec.u.nocycle.extra_u32[i] = va_arg(*args, u32);
         }
 
-        size = calc_rec_size(rec.cycle_in, rec.extra_u32 * sizeof(u32));
+        size = calc_rec_size(p->cycle_in, extra * sizeof(u32));
         relay_write(kt->rchan, &rec, size);
 }