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* [Regression] "iommu/amd: Relax locking in dma_ops path" makes tg3 ethernet transmit queue timeout
@ 2020-05-18  9:06 Kai-Heng Feng
  2020-05-18 13:32 ` Joerg Roedel
  0 siblings, 1 reply; 9+ messages in thread
From: Kai-Heng Feng @ 2020-05-18  9:06 UTC (permalink / raw)
  To: jroedel; +Cc: iommu, open list

Hi,

Broadcom ethernet tg3 unusable after commit 92d420ec028d ("iommu/amd: Relax locking in dma_ops path").
After a short period it stops:
[  122.717144] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:303 dev_watchdog+0x237/0x240()
[  122.717152] NETDEV WATCHDOG: enp3s0 (tg3): transmit queue 0 timed out

After testing the patch section by section, this is the part that caused the regression:

@@ -2578,19 +2580,8 @@ static dma_addr_t map_page(struct device *dev, struct page *page,
 
        dma_mask = *dev->dma_mask;
 
-       spin_lock_irqsave(&domain->lock, flags);
-
-       addr = __map_single(dev, domain->priv, paddr, size, dir, false,
+       return __map_single(dev, domain->priv, paddr, size, dir, false,
                            dma_mask);
-       if (addr == DMA_ERROR_CODE)
-               goto out;
-
-       domain_flush_complete(domain);
-
-out:
-       spin_unlock_irqrestore(&domain->lock, flags);
-
-       return addr;
 }

Particularly, as soon as the spinlock is removed, the issue can be reproduced.
Function domain_flush_complete() doesn't seem to affect the status.

However, the .map_page callback was removed by be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api"), so there's no easy revert for this issue.

This is still reproducible as of today's mainline kernel, v5.7-rc6.

Kai-Heng
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^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2020-08-23 13:20 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-18  9:06 [Regression] "iommu/amd: Relax locking in dma_ops path" makes tg3 ethernet transmit queue timeout Kai-Heng Feng
2020-05-18 13:32 ` Joerg Roedel
2020-05-18 14:05   ` Kai-Heng Feng
2020-05-18 15:32     ` Kai-Heng Feng
2020-06-29 12:33       ` Kai-Heng Feng
2020-08-21 13:43         ` Joerg Roedel
2020-08-21 13:50           ` Kai-Heng Feng
2020-08-21 14:43             ` Joerg Roedel
2020-08-23 13:19               ` Kai-Heng Feng

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