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Subject[PATCH 40/50] KVM: Support mixed endian machines
Date
From: Tan, Li <li.tan@intel.com>

Currently kvmtrace is not portable. This will prevent from copying a
trace file from big-endian target to little-endian workstation for analysis.
In the patch, kernel outputs metadata containing a magic number to trace
log, and changes 64-bit words to be u64 instead of a pair of u32s.

Signed-off-by: Tan Li <li.tan@intel.com>
Acked-by: Jerone Young <jyoung5@us.ibm.com>
Acked-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
---
include/linux/kvm.h | 4 ++--
virt/kvm/kvm_trace.c | 18 ++++++++++++------
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 1c908ac..0ea064c 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -318,14 +318,14 @@ struct kvm_trace_rec {
__u32 vcpu_id;
union {
struct {
- __u32 cycle_lo, cycle_hi;
+ __u64 cycle_u64;
__u32 extra_u32[KVM_TRC_EXTRA_MAX];
} cycle;
struct {
__u32 extra_u32[KVM_TRC_EXTRA_MAX];
} nocycle;
} u;
-};
+} __attribute__((packed));

#define KVMIO 0xAE

diff --git a/virt/kvm/kvm_trace.c b/virt/kvm/kvm_trace.c
index 0e49547..58141f3 100644
--- a/virt/kvm/kvm_trace.c
+++ b/virt/kvm/kvm_trace.c
@@ -72,11 +72,7 @@ static void kvm_add_trace(void *probe_private, void *call_data,
rec.cycle_in = p->cycle_in;

if (rec.cycle_in) {
- u64 cycle = 0;
-
- cycle = get_cycles();
- rec.u.cycle.cycle_lo = (u32)cycle;
- rec.u.cycle.cycle_hi = (u32)(cycle >> 32);
+ rec.u.cycle.cycle_u64 = get_cycles();

for (i = 0; i < rec.extra_u32; i++)
rec.u.cycle.extra_u32[i] = va_arg(*args, u32);
@@ -114,8 +110,18 @@ static int kvm_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
{
struct kvm_trace *kt;

- if (!relay_buf_full(buf))
+ if (!relay_buf_full(buf)) {
+ if (!prev_subbuf) {
+ /*
+ * executed only once when the channel is opened
+ * save metadata as first record
+ */
+ subbuf_start_reserve(buf, sizeof(u32));
+ *(u32 *)subbuf = 0x12345678;
+ }
+
return 1;
+ }

kt = buf->chan->private_data;
atomic_inc(&kt->lost_records);
--
1.5.6


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