97 lines
3.0 KiB
Diff
97 lines
3.0 KiB
Diff
From 8df97294d653219ad03ac031c01b723ed7f6556d Mon Sep 17 00:00:00 2001
|
|
From: Peter Jones <pjones@redhat.com>
|
|
Date: Tue, 7 Nov 2017 17:12:17 -0500
|
|
Subject: [PATCH 198/198] Make pmtimer tsc calibration not take 51 seconds to
|
|
fail.
|
|
|
|
On my laptop running at 2.4GHz, if I run a VM where tsc calibration
|
|
using pmtimer will fail presuming a broken pmtimer, it takes ~51 seconds
|
|
to do so (as measured with the stopwatch on my phone), with a tsc delta
|
|
of 0x1cd1c85300, or around 125 billion cycles.
|
|
|
|
If instead of trying to wait for 5-200ms to show up on the pmtimer, we try
|
|
to wait for 5-200us, it decides it's broken in ~0x7998f9e TSCs, aka ~2
|
|
million cycles, or more or less instantly.
|
|
|
|
Additionally, this reading the pmtimer was returning 0xffffffff anyway,
|
|
and that's obviously an invalid return. I've added a check for that and
|
|
0 so we don't bother waiting for the test if what we're seeing is dead
|
|
pins with no response at all.
|
|
|
|
Signed-off-by: Peter Jones <pjones@redhat.com>
|
|
---
|
|
grub-core/kern/i386/tsc_pmtimer.c | 43 ++++++++++++++++++++++++++++++---------
|
|
1 file changed, 33 insertions(+), 10 deletions(-)
|
|
|
|
diff --git a/grub-core/kern/i386/tsc_pmtimer.c b/grub-core/kern/i386/tsc_pmtimer.c
|
|
index c9c361699..609402b83 100644
|
|
--- a/grub-core/kern/i386/tsc_pmtimer.c
|
|
+++ b/grub-core/kern/i386/tsc_pmtimer.c
|
|
@@ -38,30 +38,53 @@ grub_pmtimer_wait_count_tsc (grub_port_t pmtimer,
|
|
grub_uint64_t start_tsc;
|
|
grub_uint64_t end_tsc;
|
|
int num_iter = 0;
|
|
+ int bad_reads = 0;
|
|
|
|
- start = grub_inl (pmtimer) & 0xffffff;
|
|
+ start = grub_inl (pmtimer) & 0x3fff;
|
|
last = start;
|
|
end = start + num_pm_ticks;
|
|
start_tsc = grub_get_tsc ();
|
|
while (1)
|
|
{
|
|
- cur = grub_inl (pmtimer) & 0xffffff;
|
|
+ cur = grub_inl (pmtimer);
|
|
+
|
|
+ /* If we get 10 reads in a row that are obviously dead pins, there's no
|
|
+ reason to do this thousands of times.
|
|
+ */
|
|
+ if (cur == 0xffffffff || cur == 0)
|
|
+ {
|
|
+ bad_reads++;
|
|
+ grub_dprintf ("pmtimer", "cur: 0x%08x bad_reads: %d\n", cur, bad_reads);
|
|
+
|
|
+ if (bad_reads == 10)
|
|
+ return 0;
|
|
+ }
|
|
+ else if (bad_reads)
|
|
+ bad_reads = 0;
|
|
+
|
|
+ cur &= 0x3fff;
|
|
+
|
|
if (cur < last)
|
|
- cur |= 0x1000000;
|
|
+ cur |= 0x4000;
|
|
num_iter++;
|
|
if (cur >= end)
|
|
{
|
|
end_tsc = grub_get_tsc ();
|
|
+ grub_dprintf ("pmtimer", "tsc delta is 0x%016lx\n",
|
|
+ end_tsc - start_tsc);
|
|
return end_tsc - start_tsc;
|
|
}
|
|
- /* Check for broken PM timer.
|
|
- 50000000 TSCs is between 5 ms (10GHz) and 200 ms (250 MHz)
|
|
- if after this time we still don't have 1 ms on pmtimer, then
|
|
- pmtimer is broken.
|
|
+ /* Check for broken PM timer. 5000 TSCs is between 5us (10GHz) and
|
|
+ 200us (250 MHz). If after this time we still don't have 1us on
|
|
+ pmtimer, then pmtimer is broken.
|
|
*/
|
|
- if ((num_iter & 0xffffff) == 0 && grub_get_tsc () - start_tsc > 5000000) {
|
|
- return 0;
|
|
- }
|
|
+ end_tsc = grub_get_tsc();
|
|
+ if ((num_iter & 0x3fff) == 0 && end_tsc - start_tsc > 5000)
|
|
+ {
|
|
+ grub_dprintf ("pmtimer", "tsc delta is 0x%016lx\n",
|
|
+ end_tsc - start_tsc);
|
|
+ return 0;
|
|
+ }
|
|
}
|
|
}
|
|
|
|
--
|
|
2.14.3
|
|
|