On Sun, Feb 18, 2018 at 12:00:01PM -0600, Scott Cheloha wrote:
> Hi,
>
> Is it bad if the olatch counts up if the host's wall clock
> is set backward? Or if the olatch makes a big jump for
> the same reason?
>
> Serious question: I don't have any EPT hardware to test
> this (sorry).
>
> While here, it looks like we can (a) roll the olatch-writing
> parts of i8253_do_readback into a loop, and (b) use the
> timespecsub macro from sys/time.h, to make the code briefer.
>
> Anyone down to test?
>
> --
> Scott Cheloha
>
Before I read through this, can you briefly explain what this is trying
to fix?
-ml
> Index: usr.sbin/vmd/i8253.c
> ===================================================================
> RCS file: /cvs/src/usr.sbin/vmd/i8253.c,v
> retrieving revision 1.17
> diff -u -p -r1.17 i8253.c
> --- usr.sbin/vmd/i8253.c 14 Aug 2017 19:46:44 -0000 1.17
> +++ usr.sbin/vmd/i8253.c 18 Feb 2018 17:53:48 -0000
> @@ -25,6 +25,7 @@
> #include <event.h>
> #include <string.h>
> #include <stddef.h>
> +#include <time.h>
> #include <unistd.h>
>
> #include "i8253.h"
> @@ -53,7 +54,7 @@ void
> i8253_init(uint32_t vm_id)
> {
> memset(&i8253_channel, 0, sizeof(struct i8253_channel));
> - gettimeofday(&i8253_channel[0].tv, NULL);
> + clock_gettime(CLOCK_MONOTONIC, &i8253_channel[0].ts);
> i8253_channel[0].start = 0xFFFF;
> i8253_channel[0].mode = TIMER_INTTC;
> i8253_channel[0].last_r = 1;
> @@ -86,8 +87,10 @@ i8253_init(uint32_t vm_id)
> void
> i8253_do_readback(uint32_t data)
> {
> - struct timeval now, delta;
> + struct timespec now, delta;
> uint64_t ns, ticks;
> + int readback_channel[3] = { TIMER_RB_C0, TIMER_RB_C1, TIMER_RB_C2 };
> + int i;
>
> /* bits are inverted here - !TIMER_RB_STATUS == enable chan readback */
> if (data & ~TIMER_RB_STATUS) {
> @@ -98,73 +101,19 @@ i8253_do_readback(uint32_t data)
>
> /* !TIMER_RB_COUNT == enable counter readback */
> if (data & ~TIMER_RB_COUNT) {
> - if (data & TIMER_RB_C0) {
> - gettimeofday(&now, NULL);
> - delta.tv_sec = now.tv_sec - i8253_channel[0].tv.tv_sec;
> - delta.tv_usec = now.tv_usec -
> - i8253_channel[0].tv.tv_usec;
> - if (delta.tv_usec < 0) {
> - delta.tv_sec--;
> - delta.tv_usec += 1000000;
> + for (i = 0; i < 3; i++) {
> + if (data & readback_channel[i]) {
> + clock_gettime(CLOCK_MONOTONIC, &now);
> + timespecsub(&now, &i8253_channel[i].ts, &delta);
> + ns = delta.tv_sec * 1000000000 + delta.tv_nsec;
> + ticks = ns / NS_PER_TICK;
> + if (i8253_channel[i].start)
> + i8253_channel[i].olatch =
> + i8253_channel[i].start -
> + ticks % i8253_channel[i].start;
> + else
> + i8253_channel[i].olatch = 0;
> }
> - if (delta.tv_usec > 1000000) {
> - delta.tv_sec++;
> - delta.tv_usec -= 1000000;
> - }
> - ns = delta.tv_usec * 1000 + delta.tv_sec * 1000000000;
> - ticks = ns / NS_PER_TICK;
> - if (i8253_channel[0].start)
> - i8253_channel[0].olatch =
> - i8253_channel[0].start -
> - ticks % i8253_channel[0].start;
> - else
> - i8253_channel[0].olatch = 0;
> - }
> -
> - if (data & TIMER_RB_C1) {
> - gettimeofday(&now, NULL);
> - delta.tv_sec = now.tv_sec - i8253_channel[1].tv.tv_sec;
> - delta.tv_usec = now.tv_usec -
> - i8253_channel[1].tv.tv_usec;
> - if (delta.tv_usec < 0) {
> - delta.tv_sec--;
> - delta.tv_usec += 1000000;
> - }
> - if (delta.tv_usec > 1000000) {
> - delta.tv_sec++;
> - delta.tv_usec -= 1000000;
> - }
> - ns = delta.tv_usec * 1000 + delta.tv_sec * 1000000000;
> - ticks = ns / NS_PER_TICK;
> - if (i8253_channel[1].start)
> - i8253_channel[1].olatch =
> - i8253_channel[1].start -
> - ticks % i8253_channel[1].start;
> - else
> - i8253_channel[1].olatch = 0;
> - }
> -
> - if (data & TIMER_RB_C2) {
> - gettimeofday(&now, NULL);
> - delta.tv_sec = now.tv_sec - i8253_channel[2].tv.tv_sec;
> - delta.tv_usec = now.tv_usec -
> - i8253_channel[2].tv.tv_usec;
> - if (delta.tv_usec < 0) {
> - delta.tv_sec--;
> - delta.tv_usec += 1000000;
> - }
> - if (delta.tv_usec > 1000000) {
> - delta.tv_sec++;
> - delta.tv_usec -= 1000000;
> - }
> - ns = delta.tv_usec * 1000 + delta.tv_sec * 1000000000;
> - ticks = ns / NS_PER_TICK;
> - if (i8253_channel[2].start)
> - i8253_channel[2].olatch =
> - i8253_channel[2].start -
> - ticks % i8253_channel[2].start;
> - else
> - i8253_channel[2].olatch = 0;
> }
> }
> }
> @@ -188,7 +137,7 @@ vcpu_exit_i8253(struct vm_run_params *vr
> uint32_t out_data;
> uint8_t sel, rw, data, mode;
> uint64_t ns, ticks;
> - struct timeval now, delta;
> + struct timespec now, delta;
> union vm_exit *vei = vrp->vrp_exit;
>
> get_input_data(vei, &out_data);
> @@ -216,21 +165,9 @@ vcpu_exit_i8253(struct vm_run_params *vr
> * rate.
> */
> if (rw == TIMER_LATCH) {
> - gettimeofday(&now, NULL);
> - delta.tv_sec = now.tv_sec -
> - i8253_channel[sel].tv.tv_sec;
> - delta.tv_usec = now.tv_usec -
> - i8253_channel[sel].tv.tv_usec;
> - if (delta.tv_usec < 0) {
> - delta.tv_sec--;
> - delta.tv_usec += 1000000;
> - }
> - if (delta.tv_usec > 1000000) {
> - delta.tv_sec++;
> - delta.tv_usec -= 1000000;
> - }
> - ns = delta.tv_usec * 1000 +
> - delta.tv_sec * 1000000000;
> + clock_gettime(CLOCK_MONOTONIC, &now);
> + timespecsub(&now, &i8253_channel[sel].ts,
> &delta);
> + ns = delta.tv_sec * 1000000000 + delta.tv_nsec;
> ticks = ns / NS_PER_TICK;
> if (i8253_channel[sel].start) {
> i8253_channel[sel].olatch =
> Index: usr.sbin/vmd/i8253.h
> ===================================================================
> RCS file: /cvs/src/usr.sbin/vmd/i8253.h,v
> retrieving revision 1.7
> diff -u -p -r1.7 i8253.h
> --- usr.sbin/vmd/i8253.h 9 Jul 2017 00:51:40 -0000 1.7
> +++ usr.sbin/vmd/i8253.h 18 Feb 2018 17:53:48 -0000
> @@ -29,7 +29,7 @@
>
> /* i8253 registers */
> struct i8253_channel {
> - struct timeval tv; /* timer start time */
> + struct timespec ts; /* timer start time */
> uint16_t start; /* starting value */
> uint16_t olatch; /* output latch */
> uint16_t ilatch; /* input latch */
