/*
 * Copyright (c) 2016 HGST, a Western Digital Company.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#ifndef _RDMA_RW_H
#define _RDMA_RW_H

#include <linux/dma-mapping.h>
#include <linux/scatterlist.h>
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>
#include <rdma/mr_pool.h>

struct rdma_rw_ctx {
	/* number of RDMA READ/WRITE WRs (not counting MR WRs) */
	u32			nr_ops;

	/* tag for the union below: */
	u8			type;

	union {
		/* for mapping a single SGE: */
		struct {
			struct ib_sge		sge;
			struct ib_rdma_wr	wr;
		} single;

		/* for mapping of multiple SGEs: */
		struct {
			struct ib_sge		*sges;
			struct ib_rdma_wr	*wrs;
		} map;

		/* for registering multiple WRs: */
		struct rdma_rw_reg_ctx {
			struct ib_sge		sge;
			struct ib_rdma_wr	wr;
			struct ib_reg_wr	reg_wr;
			struct ib_send_wr	inv_wr;
			struct ib_mr		*mr;
		} *reg;

		struct {
			struct rdma_rw_reg_ctx	data;
			struct rdma_rw_reg_ctx	prot;
			struct ib_send_wr	sig_inv_wr;
			struct ib_mr		*sig_mr;
			struct ib_sge		sig_sge;
			struct ib_sig_handover_wr sig_wr;
		} *sig;
	};
};

int rdma_rw_ctx_init(struct rdma_rw_ctx *ctx, struct ib_qp *qp, u8 port_num,
		struct scatterlist *sg, u32 sg_cnt, u32 sg_offset,
		u64 remote_addr, u32 rkey, enum dma_data_direction dir);
void rdma_rw_ctx_destroy(struct rdma_rw_ctx *ctx, struct ib_qp *qp, u8 port_num,
		struct scatterlist *sg, u32 sg_cnt,
		enum dma_data_direction dir);

int rdma_rw_ctx_signature_init(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
		u8 port_num, struct scatterlist *sg, u32 sg_cnt,
		struct scatterlist *prot_sg, u32 prot_sg_cnt,
		struct ib_sig_attrs *sig_attrs, u64 remote_addr, u32 rkey,
		enum dma_data_direction dir);
void rdma_rw_ctx_destroy_signature(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
		u8 port_num, struct scatterlist *sg, u32 sg_cnt,
		struct scatterlist *prot_sg, u32 prot_sg_cnt,
		enum dma_data_direction dir);

struct ib_send_wr *rdma_rw_ctx_wrs(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
		u8 port_num, struct ib_cqe *cqe, struct ib_send_wr *chain_wr);
int rdma_rw_ctx_post(struct rdma_rw_ctx *ctx, struct ib_qp *qp, u8 port_num,
		struct ib_cqe *cqe, struct ib_send_wr *chain_wr);

void rdma_rw_init_qp(struct ib_device *dev, struct ib_qp_init_attr *attr);
int rdma_rw_init_mrs(struct ib_qp *qp, struct ib_qp_init_attr *attr);
void rdma_rw_cleanup_mrs(struct ib_qp *qp);

#endif /* _RDMA_RW_H */
/a>/<a href='/cgit.cgi/linux/net-next.git/commit/net?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>net</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/core?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>core</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/core/gen_stats.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>gen_stats.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/net/core/gen_stats.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/net/core/gen_stats.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/net/core/gen_stats.c?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>net/core/gen_stats.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/core/gen_stats.c?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/core/gen_stats.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 'net/core/gen_stats.c')</div><table summary='diffstat' class='diffstat'>