[Intel-gfx] [PATCH igt] igt: Add basic framework for GVT-g testing

[Chris Wilson]

On Tue, Jun 21, 2016 at 12:01:02PM +0000, Wang, Zhi A wrote:
> 
> 
> > -----Original Message-----
> > From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> > Sent: Tuesday, June 21, 2016 2:55 PM
> > To: intel-gfx at lists.freedesktop.org
> > Cc: Wang, Zhi A <zhi.a.wang at intel.com>
> > Subject: Re: [PATCH igt] igt: Add basic framework for GVT-g testing
> > 
> > On Tue, Jun 21, 2016 at 12:36:06PM +0100, Chris Wilson wrote:
> > > +static bool is_gvt_enabled(void)
> > > +{
> > > +	FILE *file;
> > > +	int value;
> > > +	bool enabled = false;
> > > +
> > > +	file = fopen("/sys/module/i915/parameters/enable_gvt", "r");
> > > +	if (!file)
> > > +		return false;
> > > +
> > > +	if (fscanf(file, "%d", &value) == 1)
> > > +		enabled = value;
> > > +	fclose(file);
> > > +
> > > +	errno = 0;
> > > +	return enabled;
> > > +}
> > > +
> > > +static void unbind_fbcon(void)
> > > +{
> > > +	char buf[128];
> > > +	const char *path = "/sys/class/vtconsole";
> > > +	DIR *dir;
> > > +	struct dirent *vtcon;
> > > +
> > > +	dir = opendir(path);
> > > +	if (!dir)
> > > +		return;
> > > +
> > > +	while ((vtcon = readdir(dir))) {
> > > +		int fd, len;
> > > +
> > > +		if (strncmp(vtcon->d_name, "vtcon", 5))
> > > +			continue;
> > > +
> > > +		sprintf(buf, "%s/%s/name", path, vtcon->d_name);
> > > +		fd = open(buf, O_RDONLY);
> > > +		if (fd < 0)
> > > +			continue;
> > > +
> > > +		len = read(fd, buf, sizeof(buf) - 1);
> > > +		close(fd);
> > > +		if (len >= 0)
> > > +			buf[len] = '\0';
> > > +
> > > +		if (strstr(buf, "frame buffer device")) {
> > > +			sprintf(buf, "%s/%s/bind", path, vtcon->d_name);
> > > +			fd = open(buf, O_WRONLY);
> > > +			if (fd != -1) {
> > > +				buf[0] = '1';
> > > +				buf[1] = '\n';
> > > +				write(fd, buf, 2);
> > > +				close(fd);
> > > +			}
> > > +			break;
> > > +		}
> > > +	}
> > > +	closedir(dir);
> > > +}
> > > +
> > > +static void unload_i915(void)
> > > +{
> > > +	unbind_fbcon();
> > > +	/* pkill alsact */
> > > +
> > > +	system("/sbin/modprobe -s -r i915"); }
> > > +
> > > +bool igt_gvt_load_module(void)
> > > +{
> > > +	if (is_gvt_enabled())
> > > +		return true;
> > > +
> > > +	unload_i915();
> > > +	system("/sbin/modprobe -s i915 enable_gvt=1");
> > > +
> > > +	return is_gvt_enabled();
> > 
> > Would it be safe to put igt_gvt_unload_module() into an exit handler?
> > 
> Would you mind to elaborate your concern here? I assume you want to register igt_gvt_unload_module() via atexit(). :D

Yes. I was thinking that it would be more convenient to tests to
automatically cleanup and restore the previous state. However, an error
path is likely to leave the module in-use during our atexit handler and
so prevent us from unloading the module. Still it is one thing less to
remember when writing a test case.

The problem with the atexit handler is that it needs to be sigsafe. The
use of fopen here could be problematic for instance.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre