libipt, time: don't store MTC offset
At TMA, we store the CTC bits below the MTC range in time->mtc_offset and the
CTC bits in the MTC range in time->ctc.
The latter is used to compute last_ctc at the first MTC after TMA.
The former is subtracted from the CTC delta between last and current CTC.
We might as well add the former to last_ctc before computing the CTC delta.
This allows us to merge time->mtc_offset into time->ctc.
Change-Id: Ib01b89a8ffa4796975fb7f26c8182a3d42096fcc
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
diff --git a/libipt/internal/include/pt_time.h b/libipt/internal/include/pt_time.h
index 099f5be..9b59ec7 100644
--- a/libipt/internal/include/pt_time.h
+++ b/libipt/internal/include/pt_time.h
@@ -50,9 +50,6 @@
/* The estimated Fast Counter. */
uint64_t fc;
- /* The number of CTC ticks into the current MTC period (from TMA). */
- uint32_t mtc_offset;
-
/* The adjusted last CTC value (from MTC and TMA). */
uint32_t ctc;
diff --git a/libipt/src/pt_time.c b/libipt/src/pt_time.c
index 6bf4bd9..6066e22 100644
--- a/libipt/src/pt_time.c
+++ b/libipt/src/pt_time.c
@@ -168,7 +168,7 @@
const struct pt_packet_tma *packet,
const struct pt_config *config)
{
- uint32_t ctc, mtc_mask, mtc_offset, mtc_freq, mtc_hi;
+ uint32_t ctc, mtc_freq, mtc_hi, ctc_mask;
uint64_t fc;
if (!time || !packet || !config)
@@ -190,17 +190,16 @@
fc = packet->fc;
mtc_freq = config->mtc_freq;
- mtc_mask = (1u << mtc_freq) - 1u;
- mtc_offset = ctc & mtc_mask;
mtc_hi = mtc_freq + pt_pl_mtc_bit_size;
- /* Mask out the MTC offset and the high order bits. */
- ctc &= pt_pl_mtc_mask << mtc_freq;
+ /* A mask for the relevant CTC bits ignoring high-order bits that are
+ * not provided by MTC.
+ */
+ ctc_mask = (1u << mtc_hi) - 1u;
time->have_tma = 1;
time->base -= fc;
time->fc += fc;
- time->mtc_offset = mtc_offset;
/* If the MTC frequency is low enough that TMA provides the full CTC
* value, we can use the TMA as an MTC.
@@ -220,7 +219,7 @@
time->have_mtc = 1;
/* In both cases, we store the TMA's CTC bits until the next MTC. */
- time->ctc = time->ctc_cyc = ctc;
+ time->ctc = time->ctc_cyc = ctc & ctc_mask;
return 0;
}
@@ -229,7 +228,7 @@
const struct pt_packet_mtc *packet,
const struct pt_config *config)
{
- uint32_t last_ctc, mtc_offset, ctc, ctc_delta;
+ uint32_t last_ctc, ctc, ctc_delta;
uint64_t tsc, base;
uint8_t mtc_freq;
int errcode, have_tsc, have_tma, have_mtc;
@@ -252,7 +251,6 @@
base = time->base;
last_ctc = time->ctc;
- mtc_offset = time->mtc_offset;
mtc_freq = config->mtc_freq;
ctc = packet->ctc << mtc_freq;
@@ -264,7 +262,6 @@
/* Prepare for the next packet in case we error out below. */
time->have_mtc = 1;
time->fc = 0ull;
- time->mtc_offset = 0;
time->ctc = ctc;
/* We recover from previous CYC losses. */
@@ -324,14 +321,6 @@
return errcode;
}
- /* We don't want a wrap-around here. Something must be wrong. */
- if (ctc_delta < mtc_offset) {
- time->lost_mtc += 1;
- return -pte_bad_packet;
- }
-
- ctc_delta -= mtc_offset;
-
errcode = pt_time_ctc_fc(&tsc, ctc_delta, config);
if (errcode < 0)
return errcode;
