/*
 * RAID-6 data recovery in dual failure mode based on the XC instruction.
 *
 * Copyright IBM Corp. 2016
 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/export.h>
#include <linux/raid/pq.h>

static inline void xor_block(u8 *p1, u8 *p2)
{
	typedef struct { u8 _[256]; } addrtype;

	asm volatile(
		"	xc	0(256,%[p1]),0(%[p2])\n"
		: "+m" (*(addrtype *) p1) : "m" (*(addrtype *) p2),
		  [p1] "a" (p1), [p2] "a" (p2) : "cc");
}

/* Recover two failed data blocks. */
static void raid6_2data_recov_s390xc(int disks, size_t bytes, int faila,
		int failb, void **ptrs)
{
	u8 *p, *q, *dp, *dq;
	const u8 *pbmul;	/* P multiplier table for B data */
	const u8 *qmul;		/* Q multiplier table (for both) */
	int i;

	p = (u8 *)ptrs[disks-2];
	q = (u8 *)ptrs[disks-1];

	/* Compute syndrome with zero for the missing data pages
	   Use the dead data pages as temporary storage for
	   delta p and delta q */
	dp = (u8 *)ptrs[faila];
	ptrs[faila] = (void *)raid6_empty_zero_page;
	ptrs[disks-2] = dp;
	dq = (u8 *)ptrs[failb];
	ptrs[failb] = (void *)raid6_empty_zero_page;
	ptrs[disks-1] = dq;

	raid6_call.gen_syndrome(disks, bytes, ptrs);

	/* Restore pointer table */
	ptrs[faila]   = dp;
	ptrs[failb]   = dq;
	ptrs[disks-2] = p;
	ptrs[disks-1] = q;

	/* Now, pick the proper data tables */
	pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];

	/* Now do it... */
	while (bytes) {
		xor_block(dp, p);
		xor_block(dq, q);
		for (i = 0; i < 256; i++)
			dq[i] = pbmul[dp[i]] ^ qmul[dq[i]];
		xor_block(dp, dq);
		p += 256;
		q += 256;
		dp += 256;
		dq += 256;
		bytes -= 256;
	}
}

/* Recover failure of one data block plus the P block */
static void raid6_datap_recov_s390xc(int disks, size_t bytes, int faila,
		void **ptrs)
{
	u8 *p, *q, *dq;
	const u8 *qmul;		/* Q multiplier table */
	int i;

	p = (u8 *)ptrs[disks-2];
	q = (u8 *)ptrs[disks-1];

	/* Compute syndrome with zero for the missing data page
	   Use the dead data page as temporary storage for delta q */
	dq = (u8 *)ptrs[faila];
	ptrs[faila] = (void *)raid6_empty_zero_page;
	ptrs[disks-1] = dq;

	raid6_call.gen_syndrome(disks, bytes, ptrs);

	/* Restore pointer table */
	ptrs[faila]   = dq;
	ptrs[disks-1] = q;

	/* Now, pick the proper data tables */
	qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];

	/* Now do it... */
	while (bytes) {
		xor_block(dq, q);
		for (i = 0; i < 256; i++)
			dq[i] = qmul[dq[i]];
		xor_block(p, dq);
		p += 256;
		q += 256;
		dq += 256;
		bytes -= 256;
	}
}


const struct raid6_recov_calls raid6_recov_s390xc = {
	.data2 = raid6_2data_recov_s390xc,
	.datap = raid6_datap_recov_s390xc,
	.valid = NULL,
	.name = "s390xc",
	.priority = 1,
};
h: <a href='/cgit.cgi/linux/net-next.git/commit/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>tools</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>perf</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/tests?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>tests</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/tests/evsel-tp-sched.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>evsel-tp-sched.c</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='39cb2c9a316e77f6dfba96c543e55b6672d5a37e'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/tests/evsel-tp-sched.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/tools/perf/tests/evsel-tp-sched.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/tools/perf/tests/evsel-tp-sched.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>tools/perf/tests/evsel-tp-sched.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/perf/tests/evsel-tp-sched.c?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/tools/perf/tests/evsel-tp-sched.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'tools/perf/tests/evsel-tp-sched.c')</div><table summary='diffstat' class='diffstat'>