On Fri, Mar 15, 2019 at 10:38 AM Tzvetomir Stoyanov
<tstoyanov@xxxxxxxxxx> wrote:
>
> In order to match host and guest events, a mapping between guest VCPU
> and the host task, running this VCPU is needed. Extended existing
> struct guest to hold such mapping and added logic in read_qemu_guests()
> function to initialize it. Implemented a new internal API,
> get_guest_vcpu_pid(), to retrieve VCPU-task mapping for given VM.
>
> Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
> ---
> tracecmd/include/trace-local.h | 1 +
> tracecmd/trace-record.c | 52 ++++++++++++++++++++++++++++++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
> index 8413054..62f5e47 100644
> --- a/tracecmd/include/trace-local.h
> +++ b/tracecmd/include/trace-local.h
> @@ -245,6 +245,7 @@ int tracecmd_local_cpu_count(void);
> void tracecmd_set_clock(struct buffer_instance *instance);
> void tracecmd_remove_instance(struct buffer_instance *instance);
>
> +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu);
> /* No longer in event-utils.h */
> void __noreturn die(const char *fmt, ...); /* Can be overriden */
> void *malloc_or_die(unsigned int size); /* Can be overridden */
> diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> index 3950242..b4ea40f 100644
> --- a/tracecmd/trace-record.c
> +++ b/tracecmd/trace-record.c
> @@ -2746,10 +2746,12 @@ static bool is_digits(const char *s)
> return true;
> }
>
> +#define VCPUS_MAX 256
> struct guest {
> char *name;
> int cid;
> int pid;
> + int cpu_pid[VCPUS_MAX];
> };
>
> static struct guest *guests;
> @@ -2767,6 +2769,41 @@ static char *get_qemu_guest_name(char *arg)
> return arg;
> }
>
> +static void read_qemu_guests_pids(char *guest_task, struct guest *guest)
> +{
> + struct dirent *entry_t;
> + char path[PATH_MAX];
> + unsigned int vcpu;
> + char *buf = NULL;
> + DIR *dir;
> + FILE *ft;
> + size_t n;
> +
> + snprintf(path, sizeof(path), "/proc/%s/task", guest_task);
> + dir = opendir(path);
> + if (!dir)
> + return;
> +
> + for (entry_t = readdir(dir); entry_t; entry_t = readdir(dir)) {
> + if (!(entry_t->d_type == DT_DIR && is_digits(entry_t->d_name)))
> + continue;
> + snprintf(path, sizeof(path), "/proc/%s/task/%s/comm",
> + guest_task, entry_t->d_name);
> + ft = fopen(path, "r");
> + if (!ft)
> + continue;
> + getline(&buf, &n, ft);
We need to check the return value of getline(). It can fail (very
unlikely though) and leave the buffer allocated and the next check `if
(buf && ...)` below won't handle this case.
> + if (buf && strncmp(buf, "CPU ", 4) == 0) {
> + vcpu = atoi(buf+4);
> + if (vcpu < VCPUS_MAX)
> + guest->cpu_pid[vcpu] = atoi(entry_t->d_name);
> + }
> + free(buf);
> + fclose(ft);
> + buf = NULL;
There's no need to free() buf here, instead it can be reused for the
next iteration and freed at the very end. Reposting a version I sent
from the review of v4 of this patchset:
static void read_qemu_guest_vcpus(struct guest *guest)
{
struct dirent *entry;
char path[PATH_MAX];
size_t buf_len = 0;
char *buf = NULL;
int vcpu;
DIR *dir;
FILE *f;
snprintf(path, sizeof(path), "/proc/%d/task", guest->pid);
dir = opendir(path);
if (!dir)
return;
for (entry = readdir(dir); entry; entry = readdir(dir)) {
if (!(entry->d_type == DT_DIR && is_digits(entry->d_name)))
continue;
snprintf(path, sizeof(path), "/proc/%d/task/%s/comm",
guest->pid, entry->d_name);
f = fopen(path, "r");
if (!f)
continue;
if (getline(&buf, &buf_len, f) < 0)
goto next;
if (strncmp(buf, "CPU ", 4) != 0)
goto next;
vcpu = atoi(buf + 4);
if (!(vcpu >= 0 && vcpu < VCPUS_MAX))
goto next;
guest->cpu_pid[vcpu] = atoi(entry->d_name);
next:
fclose(f);
}
free(buf);
}
> + }
> +}
> +
> static void read_qemu_guests(void)
> {
> static bool initialized;
> @@ -2828,6 +2865,8 @@ static void read_qemu_guests(void)
> if (!is_qemu)
> goto next;
>
> + read_qemu_guests_pids(entry->d_name, &guest);
> +
> guests = realloc(guests, (guests_len + 1) * sizeof(*guests));
> if (!guests)
> die("Can not allocate guest buffer");
> @@ -2873,6 +2912,19 @@ static char *parse_guest_name(char *guest, int *cid, int *port)
> return guest;
> }
>
> +int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu)
> +{
> + int i;
> +
> + if (!guests || guest_vcpu >= VCPUS_MAX)
> + return -1;
> +
> + for (i = 0; i < guests_len; i++)
> + if (guest_cid == guests[i].cid)
> + return guests[i].cpu_pid[guest_vcpu];
> + return -1;
> +}
> +
> static void set_prio(int prio)
> {
> struct sched_param sp;
> --
> 2.20.1
>
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