Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
Merge tag 'char-misc-4.16-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull hyperv fix from Greg KH:
"This is a single hyperv bugfix for 4.16-rc7.
It resolves an issue with the ring-buffer signaling to resolve
reported problems.
It's been in linux-next for a while now with no reported issues"
* tag 'char-misc-4.16-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
Drivers: hv: vmbus: Fix ring buffer signaling
+35
-17
+35
-17
drivers/hv/ring_buffer.c
+35
-17
drivers/hv/ring_buffer.c
···
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}
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EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
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+
/* How many bytes were read in this iterator cycle */
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+
static u32 hv_pkt_iter_bytes_read(const struct hv_ring_buffer_info *rbi,
422
+
u32 start_read_index)
423
+
{
424
+
if (rbi->priv_read_index >= start_read_index)
425
+
return rbi->priv_read_index - start_read_index;
426
+
else
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+
return rbi->ring_datasize - start_read_index +
428
+
rbi->priv_read_index;
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+
}
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+
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/*
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* Update host ring buffer after iterating over packets.
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433
*/
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void hv_pkt_iter_close(struct vmbus_channel *channel)
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{
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struct hv_ring_buffer_info *rbi = &channel->inbound;
426
-
u32 orig_write_sz = hv_get_bytes_to_write(rbi);
437
+
u32 curr_write_sz, pending_sz, bytes_read, start_read_index;
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438
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/*
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* Make sure all reads are done before we update the read index since
···
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431
* is updated.
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*/
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virt_rmb();
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+
start_read_index = rbi->ring_buffer->read_index;
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rbi->ring_buffer->read_index = rbi->priv_read_index;
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+
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+
if (!rbi->ring_buffer->feature_bits.feat_pending_send_sz)
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+
return;
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/*
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* Issue a full memory barrier before making the signaling decision.
···
461
446
*/
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virt_mb();
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448
464
-
/* If host has disabled notifications then skip */
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-
if (rbi->ring_buffer->interrupt_mask)
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+
pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
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+
if (!pending_sz)
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return;
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-
if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) {
469
-
u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
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+
/*
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+
* Ensure the read of write_index in hv_get_bytes_to_write()
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+
* happens after the read of pending_send_sz.
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+
*/
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+
virt_rmb();
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+
curr_write_sz = hv_get_bytes_to_write(rbi);
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+
bytes_read = hv_pkt_iter_bytes_read(rbi, start_read_index);
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460
471
-
/*
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-
* If there was space before we began iteration,
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-
* then host was not blocked. Also handles case where
474
-
* pending_sz is zero then host has nothing pending
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-
* and does not need to be signaled.
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-
*/
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-
if (orig_write_sz > pending_sz)
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-
return;
461
+
/*
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+
* If there was space before we began iteration,
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+
* then host was not blocked.
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+
*/
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465
480
-
/* If pending write will not fit, don't give false hope. */
481
-
if (hv_get_bytes_to_write(rbi) < pending_sz)
482
-
return;
483
-
}
466
+
if (curr_write_sz - bytes_read > pending_sz)
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+
return;
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+
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+
/* If pending write will not fit, don't give false hope. */
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+
if (curr_write_sz <= pending_sz)
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+
return;
484
472
485
473
vmbus_setevent(channel);
486
474
}